Red Hat Enterprise Linux 9 Configuring and using database servers

Red Hat Enterprise Linux 9

Configuring and using database servers

Installing, configuring, backing up and migrating data on database servers

Last Updated: 2024-08-05

Red Hat Enterprise Linux 9 Configuring and using database servers

Installing, configuring, backing up and migrating data on database servers

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Abstract

Install the MariaDB, MySQL, or PostgreSQL database server on Red Hat Enterprise Linux 9.

Configure the chosen database server, back up your data, and migrate your data to a later version

of the database server.

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Table of Contents

PROVIDING FEEDBACK ON RED HAT DOCUMENTATION

CHAPTER 1. INTRODUCTION TO DATABASE SERVERS

CHAPTER 2. USING MARIADB

2.1. INSTALLING MARIADB

2.1.1. Running multiple MariaDB versions in containers

2.2. CONFIGURING MARIADB

2.3. SETTING UP TLS ENCRYPTION ON A MARIADB SERVER

2.3.1. Placing the CA certificate, server certificate, and private key on the MariaDB server

2.3.2. Configuring TLS on a MariaDB server

2.3.3. Requiring TLS encrypted connections for specific user accounts

2.4. GLOBALLY ENABLING TLS ENCRYPTION IN MARIADB CLIENTS

2.4.1. Configuring the MariaDB client to use TLS encryption by default

2.5. BACKING UP MARIADB DATA

2.5.1. Performing logical backup with mariadb-dump

2.5.2. Performing physical online backup using the Mariabackup utility

2.5.3. Restoring data using the Mariabackup utility

2.5.4. Performing file system backup

2.5.5. Replication as a backup solution

2.6. MIGRATING TO MARIADB 10.5

2.6.1. Notable differences between MariaDB 10.3 and MariaDB 10.5

2.6.2. Migrating from a RHEL 8 version of MariaDB 10.3 to a RHEL 9 version of MariaDB 10.5

2.7. UPGRADING FROM MARIADB 10.5 TO MARIADB 10.11

2.7.1. Notable differences between MariaDB 10.5 and MariaDB 10.11

2.7.2. Upgrading from a RHEL 9 version of MariaDB 10.5 to MariaDB 10.11

2.8. REPLICATING MARIADB WITH GALERA

2.8.1. Introduction to MariaDB Galera Cluster

2.8.2. Components to build MariaDB Galera Cluster

2.8.3. Deploying MariaDB Galera Cluster

2.8.4. Adding a new node to MariaDB Galera Cluster

2.8.5. Restarting MariaDB Galera Cluster

2.9. DEVELOPING MARIADB CLIENT APPLICATIONS

CHAPTER 3. USING MYSQL

3.1. INSTALLING MYSQL

3.1.1. Running multiple MySQL and MariaDB versions in containers

3.2. CONFIGURING MYSQL

3.3. SETTING UP TLS ENCRYPTION ON A MYSQL SERVER

3.3.1. Placing the CA certificate, server certificate, and private key on the MySQL server

3.3.2. Configuring TLS on a MySQL server

3.3.3. Requiring TLS encrypted connections for specific user accounts

3.4. GLOBALLY ENABLING TLS ENCRYPTION WITH CA CERTIFICATE VALIDATION IN MYSQL CLIENTS

3.4.1. Configuring the MySQL client to use TLS encryption by default

3.5. BACKING UP MYSQL DATA

3.5.1. Performing logical backup with mysqldump

3.5.2. Performing file system backup

3.5.3. Replication as a backup solution

3.6. MIGRATING TO A RHEL 9 VERSION OF MYSQL 8.0

3.7. REPLICATING MYSQL

3.7.1. Configuring a MySQL source server

3.7.2. Configuring a MySQL replica server

Table of Contents

3.7.3. Creating a replication user on the MySQL source server

3.7.4. Connecting the replica server to the source server

3.7.5. Verification

3.7.6. Additional resources

3.8. DEVELOPING MYSQL CLIENT APPLICATIONS

CHAPTER 4. USING POSTGRESQL

4.1. INSTALLING POSTGRESQL

4.1.1. Running multiple PostgreSQL versions in containers

4.2. CREATING POSTGRESQL USERS

4.3. CONFIGURING POSTGRESQL

4.4. CONFIGURING TLS ENCRYPTION ON A POSTGRESQL SERVER

4.5. BACKING UP POSTGRESQL DATA

4.5.1. Backing up PostgreSQL data with an SQL dump

4.5.1.1. Advantages and disadvantages of an SQL dump

4.5.1.2. Performing an SQL dump using pg_dump

4.5.1.3. Performing an SQL dump using pg_dumpall

4.5.1.4. Restoring a database dumped using pg_dump

4.5.1.5. Restoring databases dumped using pg_dumpall

4.5.1.6. Performing an SQL dump of a database on another server

4.5.1.7. Handling SQL errors during restore

4.5.1.8. Additional resources

4.5.2. Backing up PostgreSQL data with a file system level backup

4.5.2.1. Advantages and limitations of file system backing up

4.5.2.2. Performing file system level backing up

4.5.3. Backing up PostgreSQL data by continuous archiving

4.5.3.1. Introduction to continuous archiving

4.5.3.2. Advantages and disadvantages of continuous archiving

4.5.3.3. Setting up WAL archiving

4.5.3.4. Making a base backup

4.5.3.5. Restoring the database using a continuous archive backup

4.5.3.6. Additional resources

4.6. MIGRATING TO A RHEL 9 VERSION OF POSTGRESQL

4.6.1. Notable differences between PostgreSQL 15 and PostgreSQL 16

4.6.2. Notable differences between PostgreSQL 13 and PostgreSQL 15

4.6.3. Fast upgrade using the pg_upgrade utility

4.6.4. Dump and restore upgrade

Red Hat Enterprise Linux 9 Configuring and using database servers

Table of Contents

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Red Hat Enterprise Linux 9 Configuring and using database servers

CHAPTER 1. INTRODUCTION TO DATABASE SERVERS

A database server is a service that provides features of a database management system (DBMS). DBMS

provides utilities for database administration and interacts with end users, applications, and databases.

Red Hat Enterprise Linux 9 provides the following database management systems:

MariaDB 10.5

MariaDB 10.11 - available since RHEL 9.4

MySQL 8.0

PostgreSQL 13

PostgreSQL 15 - available since RHEL 9.2

PostgreSQL 16 - available since RHEL 9.4

Redis 6

CHAPTER 1. INTRODUCTION TO DATABASE SERVERS

CHAPTER 2. USING MARIADB

The MariaDB server is an open source fast and robust database server that is based on the MySQL

technology. MariaDB is a relational database that converts data into structured information and

provides an SQL interface for accessing data. It includes multiple storage engines and plugins, as well as

geographic information system (GIS) and JavaScript Object Notation (JSON) features.

Learn how to install and configure MariaDB on a RHEL system, how to back up MariaDB data, how to

migrate from an earlier MariaDB version, and how to replicate a database using the MariaDB Galera

Cluster.

2.1. INSTALLING MARIADB

RHEL 9.0 provides MariaDB 10.5 as the initial version of this Application Stream, which can be installed

easily as an RPM package. Additional MariaDB versions are provided as modules with a shorter life cycle

in minor releases of RHEL 9.

RHEL 9.4 introduced MariaDB 10.11 as the mariadb:10.11 module stream.

NOTE

By design, it is impossible to install more than one version (stream) of the same module in

parallel. Therefore, you must choose only one of the available streams from the mariadb

module. You can use different versions of the MariaDB database server in containers,

see Running multiple MariaDB versions in containers .

The MariaDB and MySQL database servers cannot be installed in parallel in RHEL 9 due

to conflicting RPM packages. You can use the MariaDB and MySQL database servers in

parallel in containers, see Running multiple MySQL and MariaDB versions in containers .

To install MariaDB, use the following procedure.

Procedure

1. Install MariaDB server packages:

a. For MariaDB 10.5 from the RPM package:

# dnf install mariadb-server

b. For MariaDB 10.11 by selecting stream (version) 11 from the mariadb module and

specifying the server profile, for example:

# dnf module install mariadb:10.11/server

2. Start the mariadb service:

# systemctl start mariadb.service

3. Enable the mariadb service to start at boot:

# systemctl enable mariadb.service

Red Hat Enterprise Linux 9 Configuring and using database servers

2.1.1. Running multiple MariaDB versions in containers

To run different versions of MariaDB on the same host, run them in containers because you cannot

install multiple versions (streams) of the same module in parallel.

Prerequisites

The container-tools meta-package is installed.

Procedure

1. Use your Red Hat Customer Portal account to authenticate to the registry.redhat.io registry:

# podman login registry.redhat.io

Skip this step if you are already logged in to the container registry.

2. Run MariaDB 10.5 in a container:

$ podman run -d --name <container_name> -e

MYSQL_ROOT_PASSWORD=<mariadb_root_password> -p <host_port_1>:3306

rhel9/mariadb-105

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

3. Run MariaDB 10.11 in a container:

$ podman run -d --name <container_name> -e

MYSQL_ROOT_PASSWORD=<mariadb_root_password> -p <host_port_2>:3306

rhel9/mariadb-1011

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

NOTE

The container names and host ports of the two database servers must differ.

4. To ensure that clients can access the database server on the network, open the host ports in

the firewall:

# firewall-cmd --permanent --add-port={<host_port_1>/tcp,<host_port_2>/tcp,...}

# firewall-cmd --reload

Verification

1. Display information about running containers:

$ podman ps

2. Connect to the database server and log in as root:

CHAPTER 2. USING MARIADB

# mysql -u root -p -h localhost -P <host_port> --protocol tcp

Additional resources

Building, running, and managing containers

Browse containers in the Red Hat Ecosystem Catalog

2.2. CONFIGURING MARIADB

To configure the MariaDB server for networking, use the following procedure.

Procedure

1. Edit the [mysqld] section of the /etc/my.cnf.d/mariadb-server.cnf file. You can set the

following configuration directives:

bind-address - is the address on which the server listens. Possible options are:

a host name

an IPv4 address

an IPv6 address

skip-networking - controls whether the server listens for TCP/IP connections. Possible

values are:

0 - to listen for all clients

1 - to listen for local clients only

port - the port on which MariaDB listens for TCP/IP connections.

2. Restart the mariadb service:

# systemctl restart mariadb.service

2.3. SETTING UP TLS ENCRYPTION ON A MARIADB SERVER

By default, MariaDB uses unencrypted connections. For secure connections, enable TLS support on

the MariaDB server and configure your clients to establish encrypted connections.

2.3.1. Placing the CA certificate, server certificate, and private key on the MariaDB

server

Before you can enable TLS encryption in the MariaDB server, store the certificate authority (CA)

certificate, the server certificate, and the private key on the MariaDB server.

Prerequisites

The following files in Privacy Enhanced Mail (PEM) format have been copied to the server:

The private key of the server: server.example.com.key.pem

Red Hat Enterprise Linux 9 Configuring and using database servers

The server certificate: server.example.com.crt.pem

The Certificate Authority (CA) certificate: ca.crt.pem

For details about creating a private key and certificate signing request (CSR), as well as about

requesting a certificate from a CA, see your CA’s documentation.

Procedure

1. Store the CA and server certificates in the /etc/pki/tls/certs/ directory:

# mv <path>/server.example.com.crt.pem /etc/pki/tls/certs/

# mv <path>/ca.crt.pem /etc/pki/tls/certs/

2. Set permissions on the CA and server certificate that enable the MariaDB server to read the

files:

# chmod 644 /etc/pki/tls/certs/server.example.com.crt.pem /etc/pki/tls/certs/ca.crt.pem

Because certificates are part of the communication before a secure connection is established,

any client can retrieve them without authentication. Therefore, you do not need to set strict

permissions on the CA and server certificate files.

3. Store the server’s private key in the /etc/pki/tls/private/ directory:

# mv <path>/server.example.com.key.pem /etc/pki/tls/private/

4. Set secure permissions on the server’s private key:

# chmod 640 /etc/pki/tls/private/server.example.com.key.pem

# chgrp mysql /etc/pki/tls/private/server.example.com.key.pem

If unauthorized users have access to the private key, connections to the MariaDB server are no

longer secure.

5. Restore the SELinux context:

# restorecon -Rv /etc/pki/tls/

2.3.2. Configuring TLS on a MariaDB server

To improve security, enable TLS support on the MariaDB server. As a result, clients can transmit data

with the server using TLS encryption.

Prerequisites

You installed the MariaDB server.

The mariadb service is running.

The following files in Privacy Enhanced Mail (PEM) format exist on the server and are readable

by the mysql user:

The private key of the server: /etc/pki/tls/private/server.example.com.key.pem

CHAPTER 2. USING MARIADB

The server certificate: /etc/pki/tls/certs/server.example.com.crt.pem

The Certificate Authority (CA) certificate /etc/pki/tls/certs/ca.crt.pem

The subject distinguished name (DN) or the subject alternative name (SAN) field in the server

certificate matches the server’s host name.

Procedure

1. Create the /etc/my.cnf.d/mariadb-server-tls.cnf file:

a. Add the following content to configure the paths to the private key, server and CA

certificate:

[mariadb]

ssl_key = /etc/pki/tls/private/server.example.com.key.pem

ssl_cert = /etc/pki/tls/certs/server.example.com.crt.pem

ssl_ca = /etc/pki/tls/certs/ca.crt.pem

b. If you have a Certificate Revocation List (CRL), configure the MariaDB server to use it:

ssl_crl = /etc/pki/tls/certs/example.crl.pem

c. Optional: Reject connection attempts without encryption. To enable this feature, append:

require_secure_transport = on

d. Optional: Set the TLS versions the server should support. For example, to support TLS 1.2

and TLS 1.3, append:

tls_version = TLSv1.2,TLSv1.3

By default, the server supports TLS 1.1, TLS 1.2, and TLS 1.3.

2. Restart the mariadb service:

# systemctl restart mariadb

Verification

To simplify troubleshooting, perform the following steps on the MariaDB server before you configure

the local client to use TLS encryption:

1. Verify that MariaDB now has TLS encryption enabled:

# mysql -u root -p -e "SHOW GLOBAL VARIABLES LIKE 'have_ssl';"

+---------------+-----------------+

| Variable_name | Value |

+---------------+-----------------+

| have_ssl | YES |

+---------------+-----------------+

If the have_ssl variable is set to yes, TLS encryption is enabled.

2. If you configured the MariaDB service to only support specific TLS versions, display the

Red Hat Enterprise Linux 9 Configuring and using database servers

2. If you configured the MariaDB service to only support specific TLS versions, display the

tls_version variable:

# mysql -u root -p -e "SHOW GLOBAL VARIABLES LIKE 'tls_version';"

+---------------+-----------------+

| Variable_name | Value |

+---------------+-----------------+

| tls_version | TLSv1.2,TLSv1.3 |

+---------------+-----------------+

Additional resources

Placing the CA certificate, server certificate, and private key on the MariaDB server

2.3.3. Requiring TLS encrypted connections for specific user accounts

Users that have access to sensitive data should always use a TLS-encrypted connection to avoid

sending data unencrypted over the network.

If you cannot configure on the server that a secure transport is required for all connections

(require_secure_transport = on), configure individual user accounts to require TLS encryption.

Prerequisites

The MariaDB server has TLS support enabled.

The user you configure to require secure transport exists.

Procedure

1. Connect as an administrative user to the MariaDB server:

# mysql -u root -p -h server.example.com

If your administrative user has no permissions to access the server remotely, perform the

command on the MariaDB server and connect to localhost.

2. Use the REQUIRE SSL clause to enforce that a user must connect using a TLS-encrypted

connection:

MariaDB [(none)]> ALTER USER 'example'@'%' REQUIRE SSL;

Verification

1. Connect to the server as the example user using TLS encryption:

# mysql -u example -p -h server.example.com --ssl

...

MariaDB [(none)]>

If no error is shown and you have access to the interactive MariaDB console, the connection

with TLS succeeds.

2. Attempt to connect as the example user with TLS disabled:

CHAPTER 2. USING MARIADB

# mysql -u example -p -h server.example.com --skip-ssl

ERROR 1045 (28000): Access denied for user 'example'@'server.example.com' (using

password: YES)

The server rejected the login attempt because TLS is required for this user but disabled (--skip-

ssl).

Additional resources

Setting up TLS encryption on a MariaDB server

2.4. GLOBALLY ENABLING TLS ENCRYPTION IN MARIADB CLIENTS

If your MariaDB server supports TLS encryption, configure your clients to establish only secure

connections and to verify the server certificate. This procedure describes how to enable TLS support for

all users on the server.

2.4.1. Configuring the MariaDB client to use TLS encryption by default

On RHEL, you can globally configure that the MariaDB client uses TLS encryption and verifies that the

Common Name (CN) in the server certificate matches the hostname the user connects to. This

prevents man-in-the-middle attacks.

Prerequisites

The MariaDB server has TLS support enabled.

If the certificate authority (CA) that issued the server’s certificate is not trusted by RHEL, the

CA certificate has been copied to the client.

If the MariaDB server runs RHEL 9.2 or later and the FIPS mode is enabled, this client supports

the Extended Master Secret (EMS) extension or uses TLS 1.3. TLS 1.2 connections without EMS

fail. For more information, see the TLS extension "Extended Master Secret" enforced

Knowledgebase article.

Procedure

1. If RHEL does not trust the CA that issued the server’s certificate:

a. Copy the CA certificate to the /etc/pki/ca-trust/source/anchors/ directory:

# cp <path>/ca.crt.pem /etc/pki/ca-trust/source/anchors/

b. Set permissions that enable all users to read the CA certificate file:

# chmod 644 /etc/pki/ca-trust/source/anchors/ca.crt.pem

c. Rebuild the CA trust database:

# update-ca-trust

2. Create the /etc/my.cnf.d/mariadb-client-tls.cnf file with the following content:

Red Hat Enterprise Linux 9 Configuring and using database servers

[client-mariadb]

ssl

ssl-verify-server-cert

These settings define that the MariaDB client uses TLS encryption ( ssl) and that the client

compares the hostname with the CN in the server certificate (ssl-verify-server-cert).

Verification

Connect to the server using the hostname, and display the server status:

# mysql -u root -p -h server.example.com -e status

...

SSL: Cipher in use is TLS_AES_256_GCM_SHA384

If the SSL entry contains Cipher in use is…, the connection is encrypted.

Note that the user you use in this command has permissions to authenticate remotely.

If the hostname you connect to does not match the hostname in the TLS certificate of the

server, the ssl-verify-server-cert parameter causes the connection to fail. For example, if you

connect to localhost:

# mysql -u root -p -h localhost -e status

ERROR 2026 (HY000): SSL connection error: Validation of SSL server certificate failed

Additional resources

The --ssl* parameter descriptions in the mysql(1) man page.

2.5. BACKING UP MARIADB DATA

There are two main ways to back up data from a MariaDB database in Red Hat Enterprise Linux 9:

Logical backup

Physical backup

Logical backup consists of the SQL statements necessary to restore the data. This type of backup

exports information and records in plain text files.

The main advantage of logical backup over physical backup is portability and flexibility. The data can be

restored on other hardware configurations, MariaDB versions or Database Management System

(DBMS), which is not possible with physical backups.

Note that logical backup can be performed if the mariadb.service is running. Logical backup does not

include log and configuration files.

Physical backup consists of copies of files and directories that store the content.

Physical backup has the following advantages compared to logical backup:

Output is more compact.

Backup is smaller in size.

CHAPTER 2. USING MARIADB

Backup and restore are faster.

Backup includes log and configuration files.

Note that physical backup must be performed when the mariadb.service is not running or all tables in

the database are locked to prevent changes during the backup.

You can use one of the following MariaDB backup approaches to back up data from a MariaDB

database:

Logical backup with mariadb-dump

Physical online backup using the Mariabackup utility

File system backup

Replication as a backup solution

2.5.1. Performing logical backup with mariadb-dump

The mariadb-dump client is a backup utility, which can be used to dump a database or a collection of

databases for the purpose of a backup or transfer to another database server. The output of mariadb-

dump typically consists of SQL statements to re-create the server table structure, populate it with data,

or both. mariadb-dump can also generate files in other formats, including XML and delimited text

formats, such as CSV.

To perform the mariadb-dump backup, you can use one of the following options:

Back up one or more selected databases

Back up all databases

Back up a subset of tables from one database

Procedure

To dump a single database, run:

# mariadb-dump [options] --databases db_name > backup-file.sql

To dump multiple databases at once, run:

# mariadb-dump [options] --databases db_name1 [db_name2 ...] > backup-file.sql

To dump all databases, run:

# mariadb-dump [options] --all-databases > backup-file.sql

To load one or more dumped full databases back into a server, run:

# mariadb < backup-file.sql

To load a database to a remote MariaDB server, run:

Red Hat Enterprise Linux 9 Configuring and using database servers

# mariadb --host=remote_host < backup-file.sql

To dump a subset of tables from one database, add a list of the chosen tables at the end of the

mariadb-dump command:

# mariadb-dump [options] db_name [tbl_name ...] > backup-file.sql

To load a subset of tables dumped from one database, run:

# mariadb db_name < backup-file.sql

NOTE

The db_name database must exist at this point.

To see a list of the options that mariadb-dump supports, run:

$ mariadb-dump --help

Additional resources

MariaDB Documentation - mariadb-dump

2.5.2. Performing physical online backup using the Mariabackup utility

Mariabackup is a utility based on the Percona XtraBackup technology, which enables performing

physical online backups of InnoDB, Aria, and MyISAM tables. This utility is provided by the mariadb-

backup package from the AppStream repository.

Mariabackup supports full backup capability for MariaDB server, which includes encrypted and

compressed data.

Prerequisites

The mariadb-backup package is installed on the system:

# dnf install mariadb-backup

You must provide Mariabackup with credentials for the user under which the backup will be run.

You can provide the credentials either on the command line or by a configuration file.

Users of Mariabackup must have the RELOAD, LOCK TABLES, and REPLICATION CLIENT

privileges.

To create a backup of a database using Mariabackup, use the following procedure.

Procedure

To create a backup while providing credentials on the command line, run:

$ mariabackup --backup --target-dir <backup_directory> --user <backup_user> --

password <backup_passwd>

CHAPTER 2. USING MARIADB

The target-dir option defines the directory where the backup files are stored. If you want to

perform a full backup, the target directory must be empty or not exist.

The user and password options allow you to configure the user name and the password.

To create a backup with credentials set in a configuration file:

1. Create a configuration file in the /etc/my.cnf.d/ directory, for example,

/etc/my.cnf.d/mariabackup.cnf.

2. Add the following lines into the [xtrabackup] or [mysqld] section of the new file:

[xtrabackup]

user=myuser

password=mypassword

3. Perform the backup:

$ mariabackup --backup --target-dir <backup_directory>

Additional resources

Full Backup and Restore with Mariabackup

2.5.3. Restoring data using the Mariabackup utility

When the backup is complete, you can restore the data from the backup by using the mariabackup

command with one of the following options:

--copy-back allows you to keep the original backup files.

--move-back moves the backup files to the data directory and removes the original backup

files.

To restore data using the Mariabackup utility, use the following procedure.

Prerequisites

Verify that the mariadb service is not running:

# systemctl stop mariadb.service

Verify that the data directory is empty.

Users of Mariabackup must have the RELOAD, LOCK TABLES, and REPLICATION CLIENT

privileges.

Procedure

1. Run the mariabackup command:

To restore data and keep the original backup files, use the --copy-back option:

$ mariabackup --copy-back --target-dir=/var/mariadb/backup/

Red Hat Enterprise Linux 9 Configuring and using database servers

To restore data and remove the original backup files, use the --move-back option:

$ mariabackup --move-back --target-dir=/var/mariadb/backup/

2. Fix the file permissions.

When restoring a database, Mariabackup preserves the file and directory privileges of the

backup. However, Mariabackup writes the files to disk as the user and group restoring the

database. After restoring a backup, you may need to adjust the owner of the data directory to

match the user and group for the MariaDB server, typically mysql for both.

For example, to recursively change ownership of the files to the mysql user and group:

# chown -R mysql:mysql /var/lib/mysql/

3. Start the mariadb service:

# systemctl start mariadb.service

Additional resources

Full Backup and Restore with Mariabackup

2.5.4. Performing file system backup

To create a file system backup of MariaDB data files, copy the content of the MariaDB data directory

to your backup location.

To back up also your current configuration or the log files, use the optional steps of the following

procedure.

Procedure

1. Stop the mariadb service:

# systemctl stop mariadb.service

2. Copy the data files to the required location:

# cp -r /var/lib/mysql /backup-location

3. Optionally, copy the configuration files to the required location:

# cp -r /etc/my.cnf /etc/my.cnf.d /backup-location/configuration

4. Optionally, copy the log files to the required location:

# cp /var/log/mariadb/* /backup-location/logs

5. Start the mariadb service:

# systemctl start mariadb.service

6. When loading the backed up data from the backup location to the /var/lib/mysql directory,

CHAPTER 2. USING MARIADB

6. When loading the backed up data from the backup location to the /var/lib/mysql directory,

ensure that mysql:mysql is an owner of all data in /var/lib/mysql:

# chown -R mysql:mysql /var/lib/mysql

2.5.5. Replication as a backup solution

Replication is an alternative backup solution for source servers. If a source server replicates to a replica

server, backups can be run on the replica without any impact on the source. The source can still run

while you shut down the replica and back the data up from the replica.

WARNING

Replication itself is not a sufficient backup solution. Replication protects source

servers against hardware failures, but it does not ensure protection against data

loss. It is recommended that you use any other backup solution on the replica

together with this method.

Additional resources

Replicating MariaDB with Galera

Replication as a backup solution

2.6. MIGRATING TO MARIADB 10.5

In RHEL 8, the MariaDB server is available in versions 10.3, 10.5, and 10.11, each provided by a separate

module stream. RHEL 9 provides MariaDB 10.5, MariaDB 10.11, and MySQL 8.0.

This part describes migration from a RHEL 8 version of MariaDB 10.3 to RHEL 9 version of MariaDB

10.5.

2.6.1. Notable differences between MariaDB 10.3 and MariaDB 10.5

Significant changes between MariaDB 10.3 and MariaDB 10.5 include:

MariaDB now uses the unix_socket authentication plugin by default. The plugin enables users

to use operating system credentials when connecting to MariaDB through the local UNIX

socket file.

MariaDB adds mariadb-* named binaries and mysql* symbolic links pointing to the mariadb-*

binaries. For example, the mysqladmin, mysqlaccess, and mysqlshow symlinks point to the

mariadb-admin, mariadb-access, and mariadb-show binaries, respectively.

The SUPER privilege has been split into several privileges to better align with each user role. As

a result, certain statements have changed required privileges.

In parallel replication, the slave_parallel_mode now defaults to optimistic.

In the InnoDB storage engine, defaults of the following variables have been changed:



Red Hat Enterprise Linux 9 Configuring and using database servers

In the InnoDB storage engine, defaults of the following variables have been changed:

innodb_adaptive_hash_index to OFF and innodb_checksum_algorithm to full_crc32.

MariaDB now uses the libedit implementation of the underlying software managing the

MariaDB command history (the .mysql_history file) instead of the previously used readline

library. This change impacts users working directly with the .mysql_history file. Note that

.mysql_history is a file managed by the MariaDB or MySQL applications, and users should not

work with the file directly. The human-readable appearance is coincidental.

NOTE

To increase security, you can consider not maintaining a history file. To disable

the command history recording:

1. Remove the .mysql_history file if it exists.

2. Use either of the following approaches:

Set the MYSQL_HISTFILE variable to /dev/null and include this setting

in any of your shell’s startup files.

Change the .mysql_history file to a symbolic link to /dev/null:

$ ln -s /dev/null $HOME/.mysql_history

MariaDB Galera Cluster has been upgraded to version 4 with the following notable changes:

Galera adds a new streaming replication feature, which supports replicating transactions of

unlimited size. During an execution of streaming replication, a cluster replicates a transaction in

small fragments.

Galera now fully supports Global Transaction ID (GTID).

The default value for the wsrep_on option in the /etc/my.cnf.d/galera.cnf file has changed

from 1 to 0 to prevent end users from starting wsrep replication without configuring required

additional options.

Changes to the PAM plugin in MariaDB 10.5 include:

MariaDB 10.5 adds a new version of the Pluggable Authentication Modules (PAM) plugin. The

PAM plugin version 2.0 performs PAM authentication using a separate setuid root helper

binary, which enables MariaDB to use additional PAM modules.

The helper binary can be executed only by users in the mysql group. By default, the group

contains only the mysql user. Red Hat recommends that administrators do not add more users

to the mysql group to prevent password-guessing attacks without throttling or logging through

this helper utility.

In MariaDB 10.5, the Pluggable Authentication Modules (PAM) plugin and its related files have

been moved to a new package, mariadb-pam. As a result, no new setuid root binary is

introduced on systems that do not use PAM authentication for MariaDB.

The mariadb-pam package contains both PAM plugin versions: version 2.0 is the default, and

version 1.0 is available as the auth_pam_v1 shared object library.

The mariadb-pam package is not installed by default with the MariaDB server. To make the

CHAPTER 2. USING MARIADB

The mariadb-pam package is not installed by default with the MariaDB server. To make the

PAM authentication plugin available in MariaDB 10.5, install the mariadb-pam package

manually.

2.6.2. Migrating from a RHEL 8 version of MariaDB 10.3 to a RHEL 9 version of

MariaDB 10.5

This procedure describes migrating from the MariaDB 10.3 to the MariaDB 10.5 using the mariadb-

upgrade utility.

The mariadb-upgrade utility is provided by the mariadb-server-utils subpackage, which is installed as a

dependency of the mariadb-server package.

Prerequisites

Before performing the upgrade, back up all your data stored in the MariaDB databases.

Procedure

1. Ensure that the mariadb-server package is installed on the RHEL 9 system:

# dnf install mariadb-server

2. Ensure that the mariadb service is not running on either of the source and target systems at

the time of copying data:

# systemctl stop mariadb.service

3. Copy the data from the source location to the /var/lib/mysql/ directory on the RHEL 9 target

system.

4. Set the appropriate permissions and SELinux context for copied files on the target system:

# restorecon -vr /var/lib/mysql

5. Ensure that mysql:mysql is owner of all data in the /var/lib/mysql directory:

# chown -R mysql:mysql /var/lib/mysql

6. Adjust the configuration so that option files located in /etc/my.cnf.d/ include only options valid

for MariaDB 10.5. For details, see upstream documentation for MariaDB 10.4 and MariaDB 10.5.

7. Start the MariaDB server on the target system.

When upgrading a database running standalone:

# systemctl start mariadb.service

When upgrading a Galera cluster node:

# galera_new_cluster

The mariadb service will be started automatically.

Red Hat Enterprise Linux 9 Configuring and using database servers

8. Execute the mariadb-upgrade utility to check and repair internal tables.

When upgrading a database running standalone:

$ mariadb-upgrade

When upgrading a Galera cluster node:

$ mariadb-upgrade --skip-write-binlog

IMPORTANT

There are certain risks and known problems related to an in-place upgrade. For example,

some queries might not work or they will be run in a different order than before the

upgrade. For more information about these risks and problems, and for general

information about an in-place upgrade, see MariaDB 10.5 Release Notes .

2.7. UPGRADING FROM MARIADB 10.5 TO MARIADB 10.11

This part describes migration from MariaDB 10.5 to MariaDB 10.11 within RHEL 9.

2.7.1. Notable differences between MariaDB 10.5 and MariaDB 10.11

Significant changes between MariaDB 10.5 and MariaDB 10.11 include:

A new sys_schema feature is a collection of views, functions, and procedures to provide

information about database usage.

The CREATE TABLE, ALTER TABLE, RENAME TABLE, DROP TABLE, DROP DATABASE,

and related Data Definition Language (DDL) statements are now atomic. The statement must

be fully completed, otherwise the changes are reverted. Note that when deleting multiple tables

with DROP TABLE, only each individual drop is atomic, not the full list of tables.

A new GRANT … TO PUBLIC privilege is available.

The SUPER and READ ONLY ADMIN privileges are now separate.

You can now store universally unique identifiers in the new UUID database data type.

MariaDB now supports the Secure Socket Layer (SSL) protocol version 3.

The MariaDB server now requires correctly configured SSL to start. Previously, MariaDB

silently disabled SSL and used insecure connections in case of misconfigured SSL.

MariaDB now supports the natural sort order through the natural_sort_key() function.

A new SFORMAT function is now available for arbitrary text formatting.

The utf8 character set (and related collations) is now by default an alias for utf8mb3.

MariaDB supports the Unicode Collation Algorithm (UCA) 14 collations.

systemd socket activation files for MariaDB are now available in the /usr/share/ directory.

Note that they are not a part of the default configuration in RHEL as opposed to upstream.

CHAPTER 2. USING MARIADB

Error messages now contain the MariaDB string instead of MySQL.

Error messages are now available in the Chinese language.

The default logrotate file has changed significantly. Review your configuration before migrating

to MariaDB 10.11.

For MariaDB and MySQL clients, the connection property specified on the command line (for

example, --port=3306), now forces the protocol type of communication between the client and

the server, such as tcp, socket, pipe, or memory. Previously, for example, the specified port was

ignored if a MariaDB client connected through a UNIX socket.

2.7.2. Upgrading from a RHEL 9 version of MariaDB 10.5 to MariaDB 10.11

This procedure describes upgrading from MariaDB 10.5 provided by the mariadb-server RPM package

to the mariadb:10.11 module stream using the dnf and mariadb-upgrade utilities.

The mariadb-upgrade utility is provided by the mariadb-server-utils subpackage, which is installed as a

dependency of the mariadb-server package.

Prerequisites

Before performing the upgrade, back up all your data stored in the MariaDB databases.

Procedure

1. Stop the MariaDB server:

# systemctl stop mariadb.service

2. Switch from the non-modular MariaDB 10.5 to modular MariaDB 10.11:

# dnf module switch-to mariadb:10.11

3. Adjust the configuration so that option files located in /etc/my.cnf.d/ include only options valid

for MariaDB 10.11. For details, see upstream documentation for MariaDB 10.6 and MariaDB 10.11.

4. Start the MariaDB server.

When upgrading a database running standalone:

# systemctl start mariadb.service

When upgrading a Galera cluster node:

# galera_new_cluster

The mariadb service will be started automatically.

5. Execute the mariadb-upgrade utility to check and repair internal tables.

When upgrading a database running standalone:

# mariadb-upgrade

Red Hat Enterprise Linux 9 Configuring and using database servers

When upgrading a Galera cluster node:

# mariadb-upgrade --skip-write-binlog

IMPORTANT

There are certain risks and known problems related to an in-place upgrade. For example,

some queries might not work or they will be run in a different order than before the

upgrade. For more information about these risks and problems, and for general

information about an in-place upgrade, see MariaDB 10.11 Release Notes .

2.8. REPLICATING MARIADB WITH GALERA

You can replicate a MariaDB database by using the Galera solution on Red Hat Enterprise Linux 9.

2.8.1. Introduction to MariaDB Galera Cluster

Galera replication is based on the creation of a synchronous multi-source MariaDB Galera Cluster

consisting of multiple MariaDB servers. Unlike the traditional primary/replica setup where replicas are

usually read-only, nodes in the MariaDB Galera Cluster can be all writable.

The interface between Galera replication and a MariaDB database is defined by the write set replication

API (wsrep API).

The main features of MariaDB Galera Cluster are:

Synchronous replication

Active-active multi-source topology

Read and write to any cluster node

Automatic membership control, failed nodes drop from the cluster

Automatic node joining

Parallel replication on row level

Direct client connections: users can log on to the cluster nodes, and work with the nodes

directly while the replication runs

Synchronous replication means that a server replicates a transaction at commit time by broadcasting

the write set associated with the transaction to every node in the cluster. The client (user application)

connects directly to the Database Management System (DBMS), and experiences behavior that is

similar to native MariaDB.

Synchronous replication guarantees that a change that happened on one node in the cluster happens

on other nodes in the cluster at the same time.

Therefore, synchronous replication has the following advantages over asynchronous replication:

No delay in propagation of the changes between particular cluster nodes

All cluster nodes are always consistent

CHAPTER 2. USING MARIADB

The latest changes are not lost if one of the cluster nodes crashes

Transactions on all cluster nodes are executed in parallel

Causality across the whole cluster

Additional resources

About Galera replication

What is MariaDB Galera Cluster

Getting started with MariaDB Galera Cluster

2.8.2. Components to build MariaDB Galera Cluster

To build MariaDB Galera Cluster, you must install the following packages on your system:

mariadb-server-galera - contains support files and scripts for MariaDB Galera Cluster.

mariadb-server - is patched by MariaDB upstream to include the write set replication API

(wsrep API). This API provides the interface between Galera replication and MariaDB.

galera - is patched by MariaDB upstream to add full support for MariaDB. The galera package

contains the following:

Galera Replication Library provides the whole replication functionality.

The Galera Arbitrator utility can be used as a cluster member that participates in voting in

split-brain scenarios. However, Galera Arbitrator cannot participate in the actual

replication.

Galera Systemd service and Galera wrapper script which are used for deploying the

Galera Arbitrator utility. RHEL 9 provides the upstream version of these files, located at

/usr/lib/systemd/system/garbd.service and /usr/sbin/garb-systemd.

Additional resources

Galera Replication Library

Galera Arbitrator

mysql-wsrep project

2.8.3. Deploying MariaDB Galera Cluster

You can deploy the MariaDB Galera Cluster packages and update the configuration. To form a new

cluster, you must bootstrap the first node of the cluster.

Prerequisites

Install the MariaDB Galera Cluster packages:

# dnf install mariadb-server-galera

Red Hat Enterprise Linux 9 Configuring and using database servers

As a result, the following packages are installed together with their dependencies:

mariadb-server-galera

mariadb-server

galera

For more information about these packages reqired to build MariaDB Galera Cluster, see

Components to build MariaDB Cluster .

The MariaDB server replication configuration must be updated before the system is added to a

cluster for the first time.

The default configuration is distributed in the /etc/my.cnf.d/galera.cnf file.

Before deploying MariaDB Galera Cluster, set the wsrep_cluster_address option in the

/etc/my.cnf.d/galera.cnf file on all nodes to start with the following string:

gcomm://

For the initial node, it is possible to set wsrep_cluster_address as an empty list:

wsrep_cluster_address="gcomm://"

For all other nodes, set wsrep_cluster_address to include an address to any node which is

already a part of the running cluster. For example:

wsrep_cluster_address="gcomm://10.0.0.10"

For more information about how to set Galera Cluster address, see Galera Cluster Address .

Procedure

1. Bootstrap a first node of a new cluster by running the following wrapper on that node:

# galera_new_cluster

This wrapper ensures that the MariaDB server daemon (mariadbd) runs with the --wsrep-new-

cluster option. This option provides the information that there is no existing cluster to connect

to. Therefore, the node creates a new UUID to identify the new cluster.

NOTE

The mariadb service supports a systemd method for interacting with multiple

MariaDB server processes. Therefore, in cases with multiple running MariaDB

servers, you can bootstrap a specific instance by specifying the instance name as

a suffix:

# galera_new_cluster mariadb@node1

2. Connect other nodes to the cluster by running the following command on each of the nodes:

# systemctl start mariadb

CHAPTER 2. USING MARIADB

As a result, the node connects to the cluster, and synchronizes itself with the state of the

cluster.

Additional resources

Getting started with MariaDB Galera Cluster

2.8.4. Adding a new node to MariaDB Galera Cluster

To add a new node to MariaDB Galera Cluster, use the following procedure.

Note that you can also use this procedure to reconnect an already existing node.

Procedure

On the particular node, provide an address to one or more existing cluster members in the

wsrep_cluster_address option within the [mariadb] section of the /etc/my.cnf.d/galera.cnf

configuration file :

[mariadb]

wsrep_cluster_address="gcomm://192.168.0.1"

When a new node connects to one of the existing cluster nodes, it is able to see all nodes in the

cluster.

However, preferably list all nodes of the cluster in wsrep_cluster_address.

As a result, any node can join a cluster by connecting to any other cluster node, even if one or

more cluster nodes are down. When all members agree on the membership, the cluster’s state is

changed. If the new node’s state is different from the state of the cluster, the new node

requests either an Incremental State Transfer (IST) or a State Snapshot Transfer (SST) to

ensure consistency with the other nodes.

Additional resources

Getting started with MariaDB Galera Cluster

Introduction to State Snapshot Transfers

2.8.5. Restarting MariaDB Galera Cluster

If you shut down all nodes at the same time, you stop the cluster, and the running cluster no longer

exists. However, the cluster’s data still exist.

To restart the cluster, bootstrap a first node as described in Configuring MariaDB Galera cluster .

Red Hat Enterprise Linux 9 Configuring and using database servers

WARNING

If the cluster is not bootstrapped, and mariadbd on the first node is started with

only the systemctl start mariadb command, the node tries to connect to at least

one of the nodes listed in the wsrep_cluster_address option in the

/etc/my.cnf.d/galera.cnf file. If no nodes are currently running, the restart fails.

Additional resources

Getting started with MariaDB Galera Cluster .

2.9. DEVELOPING MARIADB CLIENT APPLICATIONS

Red Hat recommends developing your MariaDB client applications against the MariaDB client library.

The development files and programs necessary to build applications against the MariaDB client library

are provided by the mariadb-connector-c-devel package.

Instead of using a direct library name, use the mariadb_config program, which is distributed in the

mariadb-connector-c-devel package. This program ensures that the correct build flags are returned.



CHAPTER 2. USING MARIADB

CHAPTER 3. USING MYSQL

The MySQL server is an open source fast and robust database server. MySQL is a relational database

that converts data into structured information and provides an SQL interface for accessing data. It

includes multiple storage engines and plugins, as well as geographic information system (GIS) and

JavaScript Object Notation (JSON) features.

Learn how to install and configure MySQL on a RHEL system, how to back up MySQL data, how to

migrate from an earlier MySQL version, and how to replicate a MySQL.

3.1. INSTALLING MYSQL

RHEL 9.0 provides MySQL 8.0 as the initial version of this Application Stream, which you can install

easily as an RPM package.

NOTE

The MySQL and MariaDB database servers cannot be installed in parallel in RHEL 9 due

to conflicting RPM packages. You can use the MySQL and MariaDB database servers in

parallel in containers, see Running multiple MySQL and MariaDB versions in containers .

To install MySQL, use the following procedure.

Procedure

1. Install MySQL server packages:

# dnf install mysql-server

2. Start the mysqld service:

# systemctl start mysqld.service

3. Enable the mysqld service to start at boot:

# systemctl enable mysqld.service

4. Recommended: To improve security when installing MySQL, run the following command:

$ mysql_secure_installation

The command launches a fully interactive script, which prompts for each step in the process.

The script enables you to improve security in the following ways:

Setting a password for root accounts

Removing anonymous users

Disallowing remote root logins (outside the local host)

3.1.1. Running multiple MySQL and MariaDB versions in containers

To run both MySQL and MariaDB on the same host, run them in containers because you cannot install

Red Hat Enterprise Linux 9 Configuring and using database servers

To run both MySQL and MariaDB on the same host, run them in containers because you cannot install

these database servers in parallel due to conflicting RPM packages.

This procedure includes MySQL 8.0 and MariaDB 10.5 as examples but you can use any MySQL or

MariaDB container version available in the Red Hat Ecosystem Catalog.

Prerequisites

The container-tools meta-package is installed.

Procedure

1. Use your Red Hat Customer Portal account to authenticate to the registry.redhat.io registry:

# podman login registry.redhat.io

Skip this step if you are already logged in to the container registry.

2. Run MySQL 8.0 in a container:

$ podman run -d --name <container_name> -e

MYSQL_ROOT_PASSWORD=<mysql_root_password> -p <host_port_1>:3306

rhel9/mysql-80

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

3. Run MariaDB 10.5 in a container:

$ podman run -d --name <container_name> -e

MYSQL_ROOT_PASSWORD=<mariadb_root_password> -p <host_port_2>:3306

rhel9/mariadb-105

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

4. Run MariaDB 10.11 in a container:

$ podman run -d --name <container_name> -e

MYSQL_ROOT_PASSWORD=<mariadb_root_password> -p <host_port_3>:3306

rhel9/mariadb-1011

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

NOTE

The container names and host ports of the two database servers must differ.

5. To ensure that clients can access the database server on the network, open the host ports in

the firewall:

CHAPTER 3. USING MYSQL

# firewall-cmd --permanent --add-port=

{<host_port_1>/tcp,<host_port_2>/tcp,<host_port_3>/tcp,...}

# firewall-cmd --reload

Verification

1. Display information about running containers:

$ podman ps

2. Connect to the database server and log in as root:

# mysql -u root -p -h localhost -P <host_port> --protocol tcp

Additional resources

Building, running, and managing containers

Browse containers in the Red Hat Ecosystem Catalog

3.2. CONFIGURING MYSQL

To configure the MySQL server for networking, use the following procedure.

Procedure

1. Edit the [mysqld] section of the /etc/my.cnf.d/mysql-server.cnf file. You can set the following

configuration directives:

bind-address - is the address on which the server listens. Possible options are:

a host name

an IPv4 address

an IPv6 address

skip-networking - controls whether the server listens for TCP/IP connections. Possible

values are:

0 - to listen for all clients

1 - to listen for local clients only

port - the port on which MySQL listens for TCP/IP connections.

2. Restart the mysqld service:

# systemctl restart mysqld.service

3.3. SETTING UP TLS ENCRYPTION ON A MYSQL SERVER

By default, MySQL uses unencrypted connections. For secure connections, enable TLS support on the

Red Hat Enterprise Linux 9 Configuring and using database servers

By default, MySQL uses unencrypted connections. For secure connections, enable TLS support on the

MySQL server and configure your clients to establish encrypted connections.

3.3.1. Placing the CA certificate, server certificate, and private key on the MySQL

server

Before you can enable TLS encryption on the MySQL server, store the certificate authority (CA)

certificate, the server certificate, and the private key on the MySQL server.

Prerequisites

The following files in Privacy Enhanced Mail (PEM) format have been copied to the server:

The private key of the server: server.example.com.key.pem

The server certificate: server.example.com.crt.pem

The Certificate Authority (CA) certificate: ca.crt.pem

For details about creating a private key and certificate signing request (CSR), as well as about

requesting a certificate from a CA, see your CA’s documentation.

Procedure

1. Store the CA and server certificates in the /etc/pki/tls/certs/ directory:

# mv <path>/server.example.com.crt.pem /etc/pki/tls/certs/

# mv <path>/ca.crt.pem /etc/pki/tls/certs/

2. Set permissions on the CA and server certificate that enable the MySQL server to read the

files:

# chmod 644 /etc/pki/tls/certs/server.example.com.crt.pem /etc/pki/tls/certs/ca.crt.pem

Because certificates are part of the communication before a secure connection is established,

any client can retrieve them without authentication. Therefore, you do not need to set strict

permissions on the CA and server certificate files.

3. Store the server’s private key in the /etc/pki/tls/private/ directory:

# mv <path>/server.example.com.key.pem /etc/pki/tls/private/

4. Set secure permissions on the server’s private key:

# chmod 640 /etc/pki/tls/private/server.example.com.key.pem

# chgrp mysql /etc/pki/tls/private/server.example.com.key.pem

If unauthorized users have access to the private key, connections to the MySQL server are no

longer secure.

5. Restore the SELinux context:

# restorecon -Rv /etc/pki/tls/

CHAPTER 3. USING MYSQL

3.3.2. Configuring TLS on a MySQL server

To improve security, enable TLS support on the MySQL server. As a result, clients can transmit data

with the server using TLS encryption.

Prerequisites

You installed the MySQL server.

The mysqld service is running.

The following files in Privacy Enhanced Mail (PEM) format exist on the server and are readable

by the mysql user:

The private key of the server: /etc/pki/tls/private/server.example.com.key.pem

The server certificate: /etc/pki/tls/certs/server.example.com.crt.pem

The Certificate Authority (CA) certificate /etc/pki/tls/certs/ca.crt.pem

The subject distinguished name (DN) or the subject alternative name (SAN) field in the server

certificate matches the server’s host name.

Procedure

1. Create the /etc/my.cnf.d/mysql-server-tls.cnf file:

a. Add the following content to configure the paths to the private key, server and CA

certificate:

[mysqld]

ssl_key = /etc/pki/tls/private/server.example.com.key.pem

ssl_cert = /etc/pki/tls/certs/server.example.com.crt.pem

ssl_ca = /etc/pki/tls/certs/ca.crt.pem

b. If you have a Certificate Revocation List (CRL), configure the MySQL server to use it:

ssl_crl = /etc/pki/tls/certs/example.crl.pem

c. Optional: Reject connection attempts without encryption. To enable this feature, append:

require_secure_transport = on

d. Optional: Set the TLS versions the server should support. For example, to support TLS 1.2

and TLS 1.3, append:

tls_version = TLSv1.2,TLSv1.3

By default, the server supports TLS 1.1, TLS 1.2, and TLS 1.3.

2. Restart the mysqld service:

# systemctl restart mysqld

Verification

To simplify troubleshooting, perform the following steps on the MySQL server before you configure the

Red Hat Enterprise Linux 9 Configuring and using database servers

To simplify troubleshooting, perform the following steps on the MySQL server before you configure the

local client to use TLS encryption:

1. Verify that MySQL now has TLS encryption enabled:

# mysql -u root -p -h <MySQL_server_hostname> -e "SHOW session status LIKE

'Ssl_cipher';"

+---------------+------------------------+

| Variable_name | Value |

+---------------+------------------------+

| Ssl_cipher | TLS_AES_256_GCM_SHA384 |

+---------------+------------------------+

2. If you configured the MySQL server to only support specific TLS versions, display the

tls_version variable:

# mysql -u root -p -e "SHOW GLOBAL VARIABLES LIKE 'tls_version';"

+---------------+-----------------+

| Variable_name | Value |

+---------------+-----------------+

| tls_version | TLSv1.2,TLSv1.3 |

+---------------+-----------------+

3. Verify that the server uses the correct CA certificate, server certificate, and private key files:

# mysql -u root -e "SHOW GLOBAL VARIABLES WHERE Variable_name REGEXP

'^ssl_ca|^ssl_cert|^ssl_key';"

+-----------------+-------------------------------------------------+

| Variable_name | Value |

+-----------------+-------------------------------------------------+

| ssl_ca | /etc/pki/tls/certs/ca.crt.pem |

| ssl_capath | |

| ssl_cert | /etc/pki/tls/certs/server.example.com.crt.pem |

| ssl_key | /etc/pki/tls/private/server.example.com.key.pem |

+-----------------+-------------------------------------------------+

Additional resources

Placing the CA certificate, server certificate, and private key on the MySQL server

3.3.3. Requiring TLS encrypted connections for specific user accounts

Users that have access to sensitive data should always use a TLS-encrypted connection to avoid

sending data unencrypted over the network.

If you cannot configure on the server that a secure transport is required for all connections

(require_secure_transport = on), configure individual user accounts to require TLS encryption.

Prerequisites

The MySQL server has TLS support enabled.

The user you configure to require secure transport exists.

CHAPTER 3. USING MYSQL

The CA certificate is stored on the client.

Procedure

1. Connect as an administrative user to the MySQL server:

# mysql -u root -p -h server.example.com

If your administrative user has no permissions to access the server remotely, perform the

command on the MySQL server and connect to localhost.

2. Use the REQUIRE SSL clause to enforce that a user must connect using a TLS-encrypted

connection:

MySQL [(none)]> ALTER USER 'example'@'%' REQUIRE SSL;

Verification

1. Connect to the server as the example user using TLS encryption:

# mysql -u example -p -h server.example.com

...

MySQL [(none)]>

If no error is shown and you have access to the interactive MySQL console, the connection with

TLS succeeds.

By default, the client automatically uses TLS encryption if the server provides it. Therefore, the

--ssl-ca=ca.crt.pem and --ssl-mode=VERIFY_IDENTITY options are not required, but improve

the security because, with these options, the client verifies the identity of the server.

2. Attempt to connect as the example user with TLS disabled:

# mysql -u example -p -h server.example.com --ssl-mode=DISABLED

ERROR 1045 (28000): Access denied for user 'example'@'server.example.com' (using

password: YES)

The server rejected the login attempt because TLS is required for this user but disabled (--ssl-

mode=DISABLED).

Additional resources

Configuring TLS on a MySQL server

3.4. GLOBALLY ENABLING TLS ENCRYPTION WITH CA CERTIFICATE

VALIDATION IN MYSQL CLIENTS

If your MySQL server supports TLS encryption, configure your clients to establish only secure

connections and to verify the server certificate. This procedure describes how to enable TLS support for

all users on the server.

3.4.1. Configuring the MySQL client to use TLS encryption by default

On RHEL, you can globally configure that the MySQL client uses TLS encryption and verifies that the

Red Hat Enterprise Linux 9 Configuring and using database servers

On RHEL, you can globally configure that the MySQL client uses TLS encryption and verifies that the

Common Name (CN) in the server certificate matches the hostname the user connects to. This

prevents man-in-the-middle attacks.

Prerequisites

The MySQL server has TLS support enabled.

The CA certificate is stored in the /etc/pki/tls/certs/ca.crt.pem file on the client.

Procedure

Create the /etc/my.cnf.d/mysql-client-tls.cnf file with the following content:

[client]

ssl-mode=VERIFY_IDENTITY

ssl-ca=/etc/pki/tls/certs/ca.crt.pem

These settings define that the MySQL client uses TLS encryption and that the client compares

the hostname with the CN in the server certificate (ssl-mode=VERIFY_IDENTITY).

Additionally, it specifies the path to the CA certificate (ssl-ca).

Verification

Connect to the server using the hostname, and display the server status:

# mysql -u root -p -h server.example.com -e status

...

SSL: Cipher in use is TLS_AES_256_GCM_SHA384

If the SSL entry contains Cipher in use is…, the connection is encrypted.

Note that the user you use in this command has permissions to authenticate remotely.

If the hostname you connect to does not match the hostname in the TLS certificate of the

server, the ssl-mode=VERIFY_IDENTITY parameter causes the connection to fail. For

example, if you connect to localhost:

# mysql -u root -p -h localhost -e status

ERROR 2026 (HY000): SSL connection error: error:0A000086:SSL routines::certificate verify

failed

Additional resources

The --ssl* parameter descriptions in the mysql(1) man page.

3.5. BACKING UP MYSQL DATA

There are two main ways to back up data from a MySQL database in Red Hat Enterprise Linux 9:

Logical backup

Physical backup

Logical backup consists of the SQL statements necessary to restore the data. This type of backup

CHAPTER 3. USING MYSQL

Logical backup consists of the SQL statements necessary to restore the data. This type of backup

exports information and records in plain text files.

The main advantage of logical backup over physical backup is portability and flexibility. The data can be

restored on other hardware configurations, MySQL versions or Database Management System (DBMS),

which is not possible with physical backups.

Note that logical backup can be performed if the mysqld.service is running. Logical backup does not

include log and configuration files.

Physical backup consists of copies of files and directories that store the content.

Physical backup has the following advantages compared to logical backup:

Output is more compact.

Backup is smaller in size.

Backup and restore are faster.

Backup includes log and configuration files.

Note that physical backup must be performed when the mysqld.service is not running or all tables in

the database are locked to prevent changes during the backup.

You can use one of the following MySQL backup approaches to back up data from a MySQL database:

Logical backup with mysqldump

File system backup

Replication as a backup solution

3.5.1. Performing logical backup with mysqldump

The mysqldump client is a backup utility, which can be used to dump a database or a collection of

databases for the purpose of a backup or transfer to another database server. The output of

mysqldump typically consists of SQL statements to re-create the server table structure, populate it

with data, or both. mysqldump can also generate files in other formats, including XML and delimited text

formats, such as CSV.

To perform the mysqldump backup, you can use one of the following options:

Back up one or more selected databases

Back up all databases

Back up a subset of tables from one database

Procedure

To dump a single database, run:

# mysqldump [options] --databases db_name > backup-file.sql

To dump multiple databases at once, run:

Red Hat Enterprise Linux 9 Configuring and using database servers

# mysqldump [options] --databases db_name1 [db_name2 ...] > backup-file.sql

To dump all databases, run:

# mysqldump [options] --all-databases > backup-file.sql

To load one or more dumped full databases back into a server, run:

# mysql < backup-file.sql

To load a database to a remote MySQL server, run:

# mysql --host=remote_host < backup-file.sql

To dump a literal,subset of tables from one database, add a list of the chosen tables at the end

of the mysqldump command:

# mysqldump [options] db_name [tbl_name ...] > backup-file.sql

To load a literal,subset of tables dumped from one database, run:

# mysql db_name < backup-file.sql

NOTE

The db_name database must exist at this point.

To see a list of the options that mysqldump supports, run:

$ mysqldump --help

Additional resources

Logical backup with mysqldump

3.5.2. Performing file system backup

To create a file system backup of MySQL data files, copy the content of the MySQL data directory to

your backup location.

To back up also your current configuration or the log files, use the optional steps of the following

procedure.

Procedure

1. Stop the mysqld service:

# systemctl stop mysqld.service

2. Copy the data files to the required location:

CHAPTER 3. USING MYSQL

# cp -r /var/lib/mysql /backup-location

3. Optionally, copy the configuration files to the required location:

# cp -r /etc/my.cnf /etc/my.cnf.d /backup-location/configuration

4. Optionally, copy the log files to the required location:

# cp /var/log/mysql/* /backup-location/logs

5. Start the mysqld service:

# systemctl start mysqld.service

6. When loading the backed up data from the backup location to the /var/lib/mysql directory,

ensure that mysql:mysql is an owner of all data in /var/lib/mysql:

# chown -R mysql:mysql /var/lib/mysql

3.5.3. Replication as a backup solution

Replication is an alternative backup solution for source servers. If a source server replicates to a replica

server, backups can be run on the replica without any impact on the source. The source can still run

while you shut down the replica and back the data up from the replica.

For instructions on how to replicate a MySQL database, see Replicating MySQL.

WARNING

Replication itself is not a sufficient backup solution. Replication protects source

servers against hardware failures, but it does not ensure protection against data

loss. It is recommended that you use any other backup solution on the replica

together with this method.

Additional resources

MySQL replication documentation

3.6. MIGRATING TO A RHEL 9 VERSION OF MYSQL 8.0

RHEL 8 contains the MySQL 8.0, MariaDB 10.3, and MariaDB 10.5 implementations of a server from

the MySQL databases family. RHEL 9 provides MySQL 8.0 and MariaDB 10.5.

This procedure describes migration from a RHEL 8 version of MySQL 8.0 to a RHEL 9 version of MySQL

8.0 using the mysql_upgrade utility. The mysql_upgrade utility is provided by the mysql-server

package.



Red Hat Enterprise Linux 9 Configuring and using database servers

Prerequisites

Before performing the upgrade, back up all your data stored in the MySQL databases. See

Backing up MySQL data.

Procedure

1. Ensure that the mysql-server package is installed on the RHEL 9 system:

# dnf install mysql-server

2. Ensure that the mysqld service is not running on either of the source and target systems at the

time of copying data:

# systemctl stop mysqld.service

3. Copy the data from the source location to the /var/lib/mysql/ directory on the RHEL 9 target

system.

4. Set the appropriate permissions and SELinux context for copied files on the target system:

# restorecon -vr /var/lib/mysql

5. Ensure that mysql:mysql is an owner of all data in the /var/lib/mysql directory:

# chown -R mysql:mysql /var/lib/mysql

6. Start the MySQL server on the target system:

# systemctl start mysqld.service

Note: In earlier versions of MySQL, the mysql_upgrade command was needed to check and

repair internal tables. This is now done automatically when you start the server.

3.7. REPLICATING MYSQL

MySQL provides various configuration options for replication, ranging from basic to advanced. This

section describes a transaction-based way to replicate in MySQL on freshly installed MySQL servers

using global transaction identifiers (GTIDs). Using GTIDs simplifies transaction identification and

consistency verification.

To set up replication in MySQL, you must:

Configure a source server

Configure a replica server

Create a replication user on the source server

Connect the replica server to the source server

IMPORTANT

CHAPTER 3. USING MYSQL

IMPORTANT

If you want to use existing MySQL servers for replication, you must first synchronize data.

See the upstream documentation for more information.

3.7.1. Configuring a MySQL source server

You can set configuration options required for a MySQL source server to properly run and replicate all

changes made on the database server.

Prerequisites

The source server is installed.

Procedure

1. Include the following options in the /etc/my.cnf.d/mysql-server.cnf file under the [mysqld]

section:

bind-address=source_ip_adress

This option is required for connections made from replicas to the source.

server-id=id

The id must be unique.

log_bin=path_to_source_server_log

This option defines a path to the binary log file of the MySQL source server. For example:

log_bin=/var/log/mysql/mysql-bin.log.

gtid_mode=ON

This option enables global transaction identifiers (GTIDs) on the server.

enforce-gtid-consistency=ON

The server enforces GTID consistency by allowing execution of only statements that can be

safely logged using a GTID.

Optional: binlog_do_db=db_name

Use this option if you want to replicate only selected databases. To replicate more than one

selected database, specify each of the databases separately:

binlog_do_db=db_name1

binlog_do_db=db_name2

binlog_do_db=db_name3

Optional: binlog_ignore_db=db_name

Use this option to exclude a specific database from replication.

2. Restart the mysqld service:

# systemctl restart mysqld.service

3.7.2. Configuring a MySQL replica server

You can set configuration options required for a MySQL replica server to ensure a successful

Red Hat Enterprise Linux 9 Configuring and using database servers

You can set configuration options required for a MySQL replica server to ensure a successful

replication.

Prerequisites

The replica server is installed.

Procedure

1. Include the following options in the /etc/my.cnf.d/mysql-server.cnf file under the [mysqld]

section:

server-id=id

The id must be unique.

relay-log=path_to_replica_server_log

The relay log is a set of log files created by the MySQL replica server during replication.

log_bin=path_to_replica_sever_log

This option defines a path to the binary log file of the MySQL replica server. For example:

log_bin=/var/log/mysql/mysql-bin.log.

This option is not required in a replica but strongly recommended.

gtid_mode=ON

This option enables global transaction identifiers (GTIDs) on the server.

enforce-gtid-consistency=ON

The server enforces GTID consistency by allowing execution of only statements that can be

safely logged using a GTID.

log-replica-updates=ON

This option ensures that updates received from the source server are logged in the replica’s

binary log.

skip-replica-start=ON

This option ensures that the replica server does not start the replication threads when the

replica server starts.

Optional: binlog_do_db=db_name

Use this option if you want to replicate only certain databases. To replicate more than one

database, specify each of the databases separately:

binlog_do_db=db_name1

binlog_do_db=db_name2

binlog_do_db=db_name3

Optional: binlog_ignore_db=db_name

Use this option to exclude a specific database from replication.

2. Restart the mysqld service:

# systemctl restart mysqld.service

CHAPTER 3. USING MYSQL

3.7.3. Creating a replication user on the MySQL source server

You must create a replication user and grant this user permissions required for replication traffic. This

procedure shows how to create a replication user with appropriate permissions. Execute these steps

only on the source server.

Prerequisites

The source server is installed and configured as described in Configuring a MySQL source

server.

Procedure

1. Create a replication user:

mysql> CREATE USER 'replication_user'@'replica_server_ip' IDENTIFIED WITH

mysql_native_password BY 'password';

2. Grant the user replication permissions:

mysql> GRANT REPLICATION SLAVE ON *.* TO

'replication_user'@'replica_server_ip';

3. Reload the grant tables in the MySQL database:

mysql> FLUSH PRIVILEGES;

4. Set the source server to read-only state:

mysql> SET @@GLOBAL.read_only = ON;

3.7.4. Connecting the replica server to the source server

On the MySQL replica server, you must configure credentials and the address of the source server. Use

the following procedure to implement the replica server.

Prerequisites

The source server is installed and configured as described in Configuring a MySQL source

server.

The replica server is installed and configured as described in Configuring a MySQL replica

server.

You have created a replication user. See Creating a replication user on the MySQL source

server.

Procedure

1. Set the replica server to read-only state:

mysql> SET @@GLOBAL.read_only = ON;

Red Hat Enterprise Linux 9 Configuring and using database servers

2. Configure the replication source:

mysql> CHANGE REPLICATION SOURCE TO

-> SOURCE_HOST='source_ip_address',

-> SOURCE_USER='replication_user',

-> SOURCE_PASSWORD='password',

-> SOURCE_AUTO_POSITION=1;

3. Start the replica thread in the MySQL replica server:

mysql> START REPLICA;

4. Unset the read-only state on both the source and replica servers:

mysql> SET @@GLOBAL.read_only = OFF;

5. Optional: Inspect the status of the replica server for debugging purposes:

mysql> SHOW REPLICA STATUS\G;

NOTE

If the replica server fails to start or connect, you can skip a certain number of

events following the binary log file position displayed in the output of the SHOW

MASTER STATUS command. For example, skip the first event from the defined

position:

mysql> SET GLOBAL SQL_SLAVE_SKIP_COUNTER=1;

and try to start the replica server again.

6. Optional: Stop the replica thread in the replica server:

mysql> STOP REPLICA;

3.7.5. Verification

1. Create an example database on the source server:

mysql> CREATE DATABASE test_db_name;

2. Verify that the test_db_name database replicates on the replica server.

3. Display status information about the binary log files of the MySQL server by executing the

following command on either of the source or replica servers:

mysql> SHOW MASTER STATUS;

The Executed_Gtid_Set column, which shows a set of GTIDs for transactions executed on the

source, must not be empty.

NOTE

CHAPTER 3. USING MYSQL

NOTE

The same set of GTIDs is displayed in the Executed_Gtid_Set row when you use

the SHOW SLAVE STATUS on the replica server.

3.7.6. Additional resources

MySQL Replication documentation

How To Set Up Replication in MySQL

Replication with Global Transaction Identifiers

3.8. DEVELOPING MYSQL CLIENT APPLICATIONS

Red Hat recommends developing your MySQL client applications against the MariaDB client library.

The communication protocol between client and server is compatible between MariaDB and MySQL.

The MariaDB client library works for most common MySQL scenarios, with the exception of a limited

number of features specific to the MySQL implementation.

The development files and programs necessary to build applications against the MariaDB client library

are provided by the mariadb-connector-c-devel package.

Instead of using a direct library name, use the mariadb_config program, which is distributed in the

mariadb-connector-c-devel package. This program ensures that the correct build flags are returned.

Red Hat Enterprise Linux 9 Configuring and using database servers

CHAPTER 4. USING POSTGRESQL

The PostgreSQL server is an open source robust and highly-extensible database server based on the

SQL language. The PostgreSQL server provides an object-relational database system that can manage

extensive datasets and a high number of concurrent users. For these reasons, PostgreSQL servers can

be used in clusters to manage high amounts of data.

The PostgreSQL server includes features for ensuring data integrity, building fault-tolerant

environments and applications. With the PostgreSQL server, you can extend a database with your own

data types, custom functions, or code from different programming languages without the need to

recompile the database.

Learn how to install and configure PostgreSQL on a RHEL system, how to back up PostgreSQL data,

and how to migrate from an earlier PostgreSQL version.

4.1. INSTALLING POSTGRESQL

RHEL 9 provides PostgreSQL 13 as the initial version of this Application Stream, which you can install

easily as an RPM package.

Additional PostgreSQL versions are provided as modules with a shorter life cycle in minor releases of

RHEL 9:

RHEL 9.2 introduced PostgreSQL 15 as the postgresql:15 module stream

RHEL 9.4 introduced PostgreSQL 16 as the postgresql:16 module stream

To install PostgreSQL, use the following procedure.

NOTE

By design, it is impossible to install more than one version (stream) of the same module in

parallel. Therefore, you must choose only one of the available streams from the

postgresql module. You can use different versions of the PostgreSQL database server

in containers, see Running multiple PostgreSQL versions in containers.

Procedure

1. Install the PostgreSQL server packages:

For PostgreSQL 13 from the RPM package:

# dnf install postgresql-server

For PostgreSQL 15 or PostgreSQL 16 by selecting stream (version) 15 or 16 from the

postgresql module and specifying the server profile, for example:

# dnf module install postgresql:16/server

The postgres superuser is created automatically.

2. Initialize the database cluster:

# postgresql-setup --initdb

CHAPTER 4. USING POSTGRESQL

Red Hat recommends storing the data in the default /var/lib/pgsql/data directory.

3. Start the postgresql service:

# systemctl start postgresql.service

4. Enable the postgresql service to start at boot:

# systemctl enable postgresql.service

IMPORTANT

If you want to upgrade from an earlier postgresql stream within RHEL 9, follow both

procedures described in Switching to a later stream and in Migrating to a RHEL 9 version

of PostgreSQL.

4.1.1. Running multiple PostgreSQL versions in containers

To run different versions of PostgreSQL on the same host, run them in containers because you cannot

install multiple versions (streams) of the same module in parallel.

This procedure includes PostgreSQL 13 and PostgreSQL 15 as examples but you can use any

PostgreSQL container version available in the Red Hat Ecosystem Catalog.

Prerequisites

The container-tools meta-package is installed.

Procedure

1. Use your Red Hat Customer Portal account to authenticate to the registry.redhat.io registry:

# podman login registry.redhat.io

Skip this step if you are already logged in to the container registry.

2. Run PostgreSQL 13 in a container:

$ podman run -d --name <container_name> -e POSTGRESQL_USER=<user_name> -e

POSTGRESQL_PASSWORD=<password> -e

POSTGRESQL_DATABASE=<database_name> -p <host_port_1>:5432

rhel9/postgresql-13

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

3. Run PostgreSQL 15 in a container:

$ podman run -d --name <container_name> -e POSTGRESQL_USER=<user_name> -e

POSTGRESQL_PASSWORD=<password> -e

POSTGRESQL_DATABASE=<database_name> -p <host_port_2>:5432

rhel9/postgresql-15

For more information about the usage of this container image, see the Red Hat Ecosystem

Red Hat Enterprise Linux 9 Configuring and using database servers

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

4. Run PostgreSQL 16 in a container:

$ podman run -d --name <container_name> -e POSTGRESQL_USER=<user_name> -e

POSTGRESQL_PASSWORD=<password> -e

POSTGRESQL_DATABASE=<database_name> -p <host_port_3>:5432

rhel9/postgresql-16

For more information about the usage of this container image, see the Red Hat Ecosystem

Catalog.

NOTE

The container names and host ports of the two database servers must differ.

5. To ensure that clients can access the database server on the network, open the host ports in

the firewall:

# firewall-cmd --permanent --add-port=

{<host_port_1>/tcp,<host_port_2>/tcp,<host_port_3>/tcp,...}

# firewall-cmd --reload

Verification

1. Display information about running containers:

$ podman ps

2. Connect to the database server and log in as root:

# psql -u postgres -p -h localhost -P <host_port> --protocol tcp

Additional resources

Building, running, and managing containers

Browse containers in the Red Hat Ecosystem Catalog

4.2. CREATING POSTGRESQL USERS

PostgreSQL users are of the following types:

The postgres UNIX system user - should be used only to run the PostgreSQL server and client

applications, such as pg_dump. Do not use the postgres system user for any interactive work

on PostgreSQL administration, such as database creation and user management.

A database superuser - the default postgres PostgreSQL superuser is not related to the

postgres system user. You can limit access of the postgres superuser in the pg_hba.conf file,

otherwise no other permission limitations exist. You can also create other database superusers.

A role with specific database access permissions:

CHAPTER 4. USING POSTGRESQL

A database user - has a permission to log in by default

A group of users - enables managing permissions for the group as a whole

Roles can own database objects (for example, tables and functions) and can assign object privileges to

other roles using SQL commands.

Standard database management privileges include SELECT, INSERT, UPDATE, DELETE, TRUNCATE,

REFERENCES, TRIGGER, CREATE, CONNECT, TEMPORARY, EXECUTE, and USAGE.

Role attributes are special privileges, such as LOGIN, SUPERUSER, CREATEDB, and CREATEROLE.

IMPORTANT

Red Hat recommends performing most tasks as a role that is not a superuser. A common

practice is to create a role that has the CREATEDB and CREATEROLE privileges and

use this role for all routine management of databases and roles.

Prerequisites

The PostgreSQL server is installed.

The database cluster is initialized.

Procedure

To create a user, set a password for the user, and assign the user the CREATEROLE and

CREATEDB permissions:

postgres=# CREATE USER mydbuser WITH PASSWORD 'mypasswd' CREATEROLE

CREATEDB;

Replace mydbuser with the username and mypasswd with the user’s password.

Additional resources

PostgreSQL database roles

PostgreSQL privileges

Configuring PostgreSQL

Example 4.1. Initializing, creating, and connecting to a PostgreSQL database

This example demonstrates how to initialize a PostgreSQL database, create a database user with

routine database management privileges, and how to create a database that is accessible from any

system account through the database user with management privileges.

1. Install the PosgreSQL server:

# dnf install postgresql-server

2. Initialize the database cluster:

Red Hat Enterprise Linux 9 Configuring and using database servers

# postgresql-setup --initdb

* Initializing database in '/var/lib/pgsql/data'

* Initialized, logs are in /var/lib/pgsql/initdb_postgresql.log

3. Set the password hashing algorithm to scram-sha-256.

a. In the /var/lib/pgsql/data/postgresql.conf file, change the following line:

#password_encryption = md5 # md5 or scram-sha-256

to:

password_encryption = scram-sha-256

b. In the /var/lib/pgsql/data/pg_hba.conf file, change the following line for the IPv4 local

connections:

host all all 127.0.0.1/32 ident

to:

host all all 127.0.0.1/32 scram-sha-256

4. Start the postgresql service:

# systemctl start postgresql.service

5. Log in as the system user named postgres:

# su - postgres

6. Start the PostgreSQL interactive terminal:

$ psql

psql (13.7)

Type "help" for help.

postgres=#

7. Optional: Obtain information about the current database connection:

postgres=# \conninfo

You are connected to database "postgres" as user "postgres" via socket in

"/var/run/postgresql" at port "5432".

8. Create a user named mydbuser, set a password for mydbuser, and assign mydbuser the

CREATEROLE and CREATEDB permissions:

postgres=# CREATE USER mydbuser WITH PASSWORD 'mypasswd' CREATEROLE

CREATEDB;

CREATE ROLE

CHAPTER 4. USING POSTGRESQL

The mydbuser user now can perform routine database management operations: create

databases and manage user indexes.

9. Log out of the interactive terminal by using the \q meta command:

postgres=# \q

10. Log out of the postgres user session:

$ logout

11. Log in to the PostgreSQL terminal as mydbuser, specify the hostname, and connect to the

default postgres database, which was created during initialization:

# psql -U mydbuser -h 127.0.0.1 -d postgres

Password for user mydbuser:

Type the password.

psql (13.7)

Type "help" for help.

postgres=>

12. Create a database named mydatabase:

postgres=> CREATE DATABASE mydatabase;

CREATE DATABASE

postgres=>

13. Log out of the session:

postgres=# \q

14. Connect to mydatabase as mydbuser:

# psql -U mydbuser -h 127.0.0.1 -d mydatabase

Password for user mydbuser:

psql (13.7)

Type "help" for help.

mydatabase=>

15. Optional: Obtain information about the current database connection:

mydatabase=> \conninfo

You are connected to database "mydatabase" as user "mydbuser" on host "127.0.0.1" at

port "5432".

4.3. CONFIGURING POSTGRESQL

In a PostgreSQL database, all data and configuration files are stored in a single directory called a

database cluster. Red Hat recommends storing all data, including configuration files, in the default

/var/lib/pgsql/data/ directory.

Red Hat Enterprise Linux 9 Configuring and using database servers

PostgreSQL configuration consists of the following files:

postgresql.conf - is used for setting the database cluster parameters.

postgresql.auto.conf - holds basic PostgreSQL settings similarly to postgresql.conf.

However, this file is under the server control. It is edited by the ALTER SYSTEM queries, and

cannot be edited manually.

pg_ident.conf - is used for mapping user identities from external authentication mechanisms

into the PostgreSQL user identities.

pg_hba.conf - is used for configuring client authentication for PostgreSQL databases.

To change the PostgreSQL configuration, use the following procedure.

Procedure

1. Edit the respective configuration file, for example, /var/lib/pgsql/data/postgresql.conf.

2. Restart the postgresql service so that the changes become effective:

# systemctl restart postgresql.service

Example 4.2. Configuring PostgreSQL database cluster parameters

This example shows basic settings of the database cluster parameters in the

/var/lib/pgsql/data/postgresql.conf file.

# This is a comment

log_connections = yes

log_destination = 'syslog'

search_path = '"$user", public'

shared_buffers = 128MB

password_encryption = scram-sha-256

Example 4.3. Setting client authentication in PostgreSQL

This example demonstrates how to set client authentication in the /var/lib/pgsql/data/pg_hba.conf

file.

# TYPE DATABASE USER ADDRESS METHOD

local all all trust

host postgres all 192.168.93.0/24 ident

host all all .example.com scram-sha-256

4.4. CONFIGURING TLS ENCRYPTION ON A POSTGRESQL SERVER

By default, PostgreSQL uses unencrypted connections. For more secure connections, you can enable

Transport Layer Security (TLS) support on the PostgreSQL server and configure your clients to

establish encrypted connections.

Prerequisites

CHAPTER 4. USING POSTGRESQL

Prerequisites

The PostgreSQL server is installed.

The database cluster is initialized.

If the server runs RHEL 9.2 or later and the FIPS mode is enabled, clients must either support

the Extended Master Secret (EMS) extension or use TLS 1.3. TLS 1.2 connections without EMS

fail. For more information, see the TLS extension "Extended Master Secret" enforced

Knowledgebase article.

Procedure

1. Install the OpenSSL library:

# dnf install openssl

2. Generate a TLS certificate and a key:

# openssl req -new -x509 -days 365 -nodes -text -out server.crt \

-keyout server.key -subj "/CN=dbhost.yourdomain.com"

Replace dbhost.yourdomain.com with your database host and domain name.

3. Copy your signed certificate and your private key to the required locations on the database

server:

# cp server.{key,crt} /var/lib/pgsql/data/.

4. Change the owner and group ownership of the signed certificate and your private key to the

postgres user:

# chown postgres:postgres /var/lib/pgsql/data/server.{key,crt}

5. Restrict the permissions for your private key so that it is readable only by the owner:

# chmod 0400 /var/lib/pgsql/data/server.key

6. Set the password hashing algorithm to scram-sha-256 by changing the following line in the

/var/lib/pgsql/data/postgresql.conf file:

#password_encryption = md5 # md5 or scram-sha-256

to:

password_encryption = scram-sha-256

7. Configure PostgreSQL to use SSL/TLS by changing the following line in the

/var/lib/pgsql/data/postgresql.conf file:

#ssl = off

to:

Red Hat Enterprise Linux 9 Configuring and using database servers

ssl=on

8. Restrict access to all databases to accept only connections from clients using TLS by changing

the following line for the IPv4 local connections in the /var/lib/pgsql/data/pg_hba.conf file:

host all all 127.0.0.1/32 ident

to:

hostssl all all 127.0.0.1/32 scram-sha-256

Alternatively, you can restrict access for a single database and a user by adding the following

new line:

hostssl mydatabase mydbuser 127.0.0.1/32 scram-sha-256

Replace mydatabase with the database name and mydbuser with the username.

9. Make the changes effective by restarting the postgresql service:

# systemctl restart postgresql.service

Verification

To manually verify that the connection is encrypted:

1. Connect to the PostgreSQL database as the mydbuser user, specify the hostname and the

database name:

$ psql -U mydbuser -h 127.0.0.1 -d mydatabase

Password for user mydbuser:

Replace mydatabase with the database name and mydbuser with the username.

2. Obtain information about the current database connection:

mydbuser=> \conninfo

You are connected to database "mydatabase" as user "mydbuser" on host "127.0.0.1" at

port "5432".

SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256,

compression: off)

You can write a simple application that verifies whether a connection to PostgreSQL is

encrypted. This example demonstrates such an application written in C that uses the libpq

client library, which is provided by the libpq-devel package:

#include <stdio.h>

#include <stdlib.h>

#include <libpq-fe.h>

int main(int argc, char* argv[])

{

//Create connection

CHAPTER 4. USING POSTGRESQL

PGconn* connection = PQconnectdb("hostaddr=127.0.0.1 password=mypassword port=5432

dbname=mydatabase user=mydbuser");

if (PQstatus(connection) ==CONNECTION_BAD)

{

printf("Connection error\n");

PQfinish(connection);

return -1; //Execution of the program will stop here

}

printf("Connection ok\n");

//Verify TLS

if (PQsslInUse(connection)){

printf("TLS in use\n");

printf("%s\n", PQsslAttribute(connection,"protocol"));

}

//End connection

PQfinish(connection);

printf("Disconnected\n");

return 0;

}

Replace mypassword with the password, mydatabase with the database name, and mydbuser

with the username.

NOTE

You must load the pq libraries for compilation by using the -lpq option. For

example, to compile the application by using the GCC compiler:

$ gcc source_file.c -lpq -o myapplication

where the source_file.c contains the example code above, and myapplication is

the name of your application for verifying secured PostgreSQL connection.

Example 4.4. Initializing, creating, and connecting to a PostgreSQL database using TLS

encryption

This example demonstrates how to initialize a PostgreSQL database, create a database user and a

database, and how to connect to the database using a secured connection.

1. Install the PosgreSQL server:

# dnf install postgresql-server

2. Initialize the database cluster:

# postgresql-setup --initdb

* Initializing database in '/var/lib/pgsql/data'

* Initialized, logs are in /var/lib/pgsql/initdb_postgresql.log

3. Install the OpenSSL library:

# dnf install openssl

Red Hat Enterprise Linux 9 Configuring and using database servers

4. Generate a TLS certificate and a key:

# openssl req -new -x509 -days 365 -nodes -text -out server.crt \

-keyout server.key -subj "/CN=dbhost.yourdomain.com"

Replace dbhost.yourdomain.com with your database host and domain name.

5. Copy your signed certificate and your private key to the required locations on the database

server:

# cp server.{key,crt} /var/lib/pgsql/data/.

6. Change the owner and group ownership of the signed certificate and your private key to the

postgres user:

# chown postgres:postgres /var/lib/pgsql/data/server.{key,crt}

7. Restrict the permissions for your private key so that it is readable only by the owner:

# chmod 0400 /var/lib/pgsql/data/server.key

8. Set the password hashing algorithm to scram-sha-256. In the

/var/lib/pgsql/data/postgresql.conf file, change the following line:

#password_encryption = md5 # md5 or scram-sha-256

to:

password_encryption = scram-sha-256

9. Configure PostgreSQL to use SSL/TLS. In the /var/lib/pgsql/data/postgresql.conf file,

change the following line:

#ssl = off

to:

ssl=on

10. Start the postgresql service:

# systemctl start postgresql.service

11. Log in as the system user named postgres:

# su - postgres

12. Start the PostgreSQL interactive terminal as the postgres user:

$ psql -U postgres

psql (13.7)

Type "help" for help.

CHAPTER 4. USING POSTGRESQL

postgres=#

13. Create a user named mydbuser and set a password for mydbuser:

postgres=# CREATE USER mydbuser WITH PASSWORD 'mypasswd';

CREATE ROLE

postgres=#

14. Create a database named mydatabase:

postgres=# CREATE DATABASE mydatabase;

CREATE DATABASE

postgres=#

15. Grant all permissions to the mydbuser user:

postgres=# GRANT ALL PRIVILEGES ON DATABASE mydatabase TO mydbuser;

GRANT

postgres=#

16. Log out of the interactive terminal:

postgres=# \q

17. Log out of the postgres user session:

$ logout

18. Restrict access to all databases to accept only connections from clients using TLS by

changing the following line for the IPv4 local connections in the

/var/lib/pgsql/data/pg_hba.conf file:

host all all 127.0.0.1/32 ident

to:

hostssl all all 127.0.0.1/32 scram-sha-256

19. Make the changes effective by restarting the postgresql service:

# systemctl restart postgresql.service

20. Connect to the PostgreSQL database as the mydbuser user, specify the hostname and the

database name:

$ psql -U mydbuser -h 127.0.0.1 -d mydatabase

Password for user mydbuser:

psql (13.7)

SSL connection (protocol: TLSv1.3, cipher: TLS_AES_256_GCM_SHA384, bits: 256,

compression: off)

Red Hat Enterprise Linux 9 Configuring and using database servers

Type "help" for help.

mydatabase=>

4.5. BACKING UP POSTGRESQL DATA

To back up PostgreSQL data, use one of the following approaches:

SQL dump

See Backing up with SQL dump.

File system level backup

See File system level backup .

Continuous archiving

See Continuous archiving.

4.5.1. Backing up PostgreSQL data with an SQL dump

The SQL dump method is based on generating a dump file with SQL commands. When a dump is

uploaded back to the database server, it recreates the database in the same state as it was at the time

of the dump.

The SQL dump is ensured by the following PostgreSQL client applications:

pg_dump dumps a single database without cluster-wide information about roles or tablespaces

pg_dumpall dumps each database in a given cluster and preserves cluster-wide data, such as

role and tablespace definitions.

By default, the pg_dump and pg_dumpall commands write their results into the standard output. To

store the dump in a file, redirect the output to an SQL file. The resulting SQL file can be either in a text

format or in other formats that allow for parallelism and for more detailed control of object restoration.

You can perform the SQL dump from any remote host that has access to the database.

4.5.1.1. Advantages and disadvantages of an SQL dump

An SQL dump has the following advantages compared to other PostgreSQL backup methods:

An SQL dump is the only PostgreSQL backup method that is not server version-specific. The

output of the pg_dump utility can be reloaded into later versions of PostgreSQL, which is not

possible for file system level backups or continuous archiving.

An SQL dump is the only method that works when transferring a database to a different

machine architecture, such as going from a 32-bit to a 64-bit server.

An SQL dump provides internally consistent dumps. A dump represents a snapshot of the

database at the time pg_dump began running.

The pg_dump utility does not block other operations on the database when it is running.

A disadvantage of an SQL dump is that it takes more time compared to file system level backup.

CHAPTER 4. USING POSTGRESQL

4.5.1.2. Performing an SQL dump using pg_dump

To dump a single database without cluster-wide information, use the pg_dump utility.

Prerequisites

You must have read access to all tables that you want to dump. To dump the entire database,

you must run the commands as the postgres superuser or a user with database administrator

privileges.

Procedure

Dump a database without cluster-wide information:

$ pg_dump dbname > dumpfile

To specify which database server pg_dump will contact, use the following command-line options:

The -h option to define the host.

The default host is either the local host or what is specified by the PGHOST environment

variable.

The -p option to define the port.

The default port is indicated by the PGPORT environment variable or the compiled-in default.

4.5.1.3. Performing an SQL dump using pg_dumpall

To dump each database in a given database cluster and to preserve cluster-wide data, use the

pg_dumpall utility.

Prerequisites

You must run the commands as the postgres superuser or a user with database administrator

privileges.

Procedure

Dump all databases in the database cluster and preserve cluster-wide data:

$ pg_dumpall > dumpfile

To specify which database server pg_dumpall will contact, use the following command-line options:

The -h option to define the host.

The default host is either the local host or what is specified by the PGHOST environment

variable.

The -p option to define the port.

The default port is indicated by the PGPORT environment variable or the compiled-in default.

The -l option to define the default database.

This option enables you to choose a default database different from the postgres database

created automatically during initialization.

Red Hat Enterprise Linux 9 Configuring and using database servers

4.5.1.4. Restoring a database dumped using pg_dump

To restore a database from an SQL dump that you dumped using the pg_dump utility, follow the steps

below.

Prerequisites

You must run the commands as the postgres superuser or a user with database administrator

privileges.

Procedure

1. Create a new database:

$ createdb dbname

2. Verify that all users who own objects or were granted permissions on objects in the dumped

database already exist. If such users do not exist, the restore fails to recreate the objects with

the original ownership and permissions.

3. Run the psql utility to restore a text file dump created by the pg_dump utility:

$ psql dbname < dumpfile

where dumpfile is the output of the pg_dump command. To restore a non-text file dump, use

the pg_restore utility instead:

$ pg_restore non-plain-text-file

4.5.1.5. Restoring databases dumped using pg_dumpall

To restore data from a database cluster that you dumped using the pg_dumpall utility, follow the steps

below.

Prerequisites

You must run the commands as the postgres superuser or a user with database administrator

privileges.

Procedure

1. Ensure that all users who own objects or were granted permissions on objects in the dumped

databases already exist. If such users do not exist, the restore fails to recreate the objects with

the original ownership and permissions.

2. Run the psql utility to restore a text file dump created by the pg_dumpall utility:

$ psql < dumpfile

where dumpfile is the output of the pg_dumpall command.

4.5.1.6. Performing an SQL dump of a database on another server

CHAPTER 4. USING POSTGRESQL

Dumping a database directly from one server to another is possible because pg_dump and psql can

write to and read from pipes.

Procedure

To dump a database from one server to another, run:

$ pg_dump -h host1 dbname | psql -h host2 dbname

4.5.1.7. Handling SQL errors during restore

By default, psql continues to execute if an SQL error occurs, causing the database to restore only

partially.

To change the default behavior, use one of the following approaches when restoring a dump.

Prerequisites

You must run the commands as the postgres superuser or a user with database administrator

privileges.

Procedure

Make psql exit with an exit status of 3 if an SQL error occurs by setting the ON_ERROR_STOP

variable:

$ psql --set ON_ERROR_STOP=on dbname < dumpfile

Specify that the whole dump is restored as a single transaction so that the restore is either fully

completed or canceled.

When restoring a text file dump using the psql utility:

$ psql -1

When restoring a non-text file dump using the pg_restore utility:

$ pg_restore -e

Note that when using this approach, even a minor error can cancel a restore operation that

has already run for many hours.

4.5.1.8. Additional resources

PostgreSQL Documentation - SQL dump

4.5.2. Backing up PostgreSQL data with a file system level backup

To create a file system level backup, copy PostgreSQL database files to another location. For example,

you can use any of the following approaches:

Create an archive file using the tar utility.

Red Hat Enterprise Linux 9 Configuring and using database servers

Copy the files to a different location using the rsync utility.

Create a consistent snapshot of the data directory.

4.5.2.1. Advantages and limitations of file system backing up

File system level backing up has the following advantage compared to other PostgreSQL backup

methods:

File system level backing up is usually faster than an SQL dump.

File system level backing up has the following limitations compared to other PostgreSQL backup

methods:

This backing up method is not suitable when you want to upgrade from RHEL 8 to RHEL 9 and

migrate your data to the upgraded system. File system level backup is specific to an architecture

and a RHEL major version. You can restore your data on your RHEL 8 system if the upgrade is

not successful but you cannot restore the data on a RHEL 9 system.

The database server must be shut down before backing up and restoring data.

Backing up and restoring certain individual files or tables is impossible. Backing up a file system

works only for complete backing up and restoring of an entire database cluster.

4.5.2.2. Performing file system level backing up

To perform file system level backing up, use the following procedure.

Procedure

1. Choose the location of a database cluster and initialize this cluster:

# postgresql-setup --initdb

2. Stop the postgresql service:

# systemctl stop postgresql.service

3. Use any method to create a file system backup, for example a tar archive:

$ tar -cf backup.tar /var/lib/pgsql/data

4. Start the postgresql service:

# systemctl start postgresql.service

Additional resources

PostgreSQL Documentation - file system level backup

4.5.3. Backing up PostgreSQL data by continuous archiving

4.5.3.1. Introduction to continuous archiving

CHAPTER 4. USING POSTGRESQL

PostgreSQL records every change made to the database’s data files into a write ahead log (WAL) file

that is available in the pg_wal/ subdirectory of the cluster’s data directory. This log is intended primarily

for a crash recovery. After a crash, the log entries made since the last checkpoint can be used for

restoring the database to a consistency.

The continuous archiving method, also known as an online backup, combines the WAL files with a copy

of the database cluster in the form of a base backup performed on a running server or a file system level

backup.

If a database recovery is needed, you can restore the database from the copy of the database cluster

and then replay log from the backed up WAL files to bring the system to the current state.

With the continuous archiving method, you must keep a continuous sequence of all archived WAL files

that extends at minimum back to the start time of your last base backup. Therefore the ideal frequency

of base backups depends on:

The storage volume available for archived WAL files.

The maximum possible duration of data recovery in situations when recovery is necessary. In

cases with a long period since the last backup, the system replays more WAL segments, and the

recovery therefore takes more time.

NOTE

You cannot use pg_dump and pg_dumpall SQL dumps as a part of a continuous

archiving backup solution. SQL dumps produce logical backups and do not contain

enough information to be used by a WAL replay.

To perform a database backup and restore using the continuous archiving method, follow these

instructions:

1. Set up and test your procedure for archiving WAL files - see WAL archiving.

2. Perform a base backup - see base backup.

To restore your data, follow instructions in Restoring database with continuous archiving.

4.5.3.2. Advantages and disadvantages of continuous archiving

Continuous archiving has the following advantages compared to other PostgreSQL backup methods:

With the continuous backup method, it is possible to use a base backup that is not entirely

consistent because any internal inconsistency in the backup is corrected by the log replay.

Therefore you can perform a base backup on a running PostgreSQL server.

A file system snapshot is not needed; tar or a similar archiving utility is sufficient.

Continuous backup can be achieved by continuing to archive the WAL files because the

sequence of WAL files for the log replay can be indefinitely long. This is particularly valuable for

large databases.

Continuous backup supports point-in-time recovery. It is not necessary to replay the WAL

entries to the end. The replay can be stopped at any point and the database can be restored to

its state at any time since the base backup was taken.

If the series of WAL files are continuously available to another machine that has been loaded

Red Hat Enterprise Linux 9 Configuring and using database servers

If the series of WAL files are continuously available to another machine that has been loaded

with the same base backup file, it is possible to restore the other machine with a nearly-current

copy of the database at any point.

Continuous archiving has the following disadvantages compared to other PostgreSQL backup methods:

Continuous backup method supports only restoration of an entire database cluster, not a

subset.

Continuous backup requires extensive archival storage.

4.5.3.3. Setting up WAL archiving

A running PostgreSQL server produces a sequence of write ahead log (WAL) records. The server

physically divides this sequence into WAL segment files, which are given numeric names that reflect

their position in the WAL sequence. Without WAL archiving, the segment files are reused and renamed

to higher segment numbers.

When archiving WAL data, the contents of each segment file are captured and saved at a new location

before the segment file is reused. You have multiple options where to save the content, such as an NFS-

mounted directory on another machine, a tape drive, or a CD.

Note that WAL records do not include changes to configuration files.

To enable WAL archiving, use the following procedure.

Procedure

1. In the /var/lib/pgsql/data/postgresql.conf file:

a. Set the wal_level configuration parameter to replica or higher.

b. Set the archive_mode parameter to on.

c. Specify the shell command in the archive_command configuration parameter. You can use

the cp command, another command, or a shell script.

2. Restart the postgresql service to enable the changes:

# systemctl restart postgresql.service

3. Test your archive command and ensure it does not overwrite an existing file and that it returns a

nonzero exit status if it fails.

4. To protect your data, ensure that the segment files are archived into a directory that does not

have group or world read access.

NOTE

CHAPTER 4. USING POSTGRESQL

NOTE

The archive command is executed only on completed WAL segments. A server that

generates little WAL traffic can have a substantial delay between the completion of a

transaction and its safe recording in archive storage. To limit how old unarchived data can

be, you can:

Set the archive_timeout parameter to force the server to switch to a new WAL

segment file with a given frequency.

Use the pg_switch_wal parameter to force a segment switch to ensure that a

transaction is archived immediately after it finishes.

Example 4.5. Shell command for archiving WAL segments

This example shows a simple shell command you can set in the archive_command configuration

parameter.

The following command copies a completed segment file to the required location:

archive_command = 'test ! -f /mnt/server/archivedir/%f && cp %p /mnt/server/archivedir/%f'

where the %p parameter is replaced by the relative path to the file to archive and the %f parameter

is replaced by the file name.

This command copies archivable WAL segments to the /mnt/server/archivedir/ directory. After

replacing the %p and %f parameters, the executed command looks as follows:

test ! -f /mnt/server/archivedir/00000001000000A900000065 && cp

pg_wal/00000001000000A900000065 /mnt/server/archivedir/00000001000000A900000065

A similar command is generated for each new file that is archived.

Additional resources

PostgreSQL 16 Documentation

4.5.3.4. Making a base backup

You can create a base backup in several ways. The simplest way of performing a base backup is using the

pg_basebackup utility on a running PostgreSQL server.

The base backup process creates a backup history file that is stored into the WAL archive area and is

named after the first WAL segment file that you need for the base backup.

The backup history file is a small text file containing the starting and ending times, and WAL segments of

the backup. If you used the label string to identify the associated dump file, you can use the backup

history file to determine which dump file to restore.

NOTE

Consider keeping several backup sets to be certain that you can recover your data.

Red Hat Enterprise Linux 9 Configuring and using database servers

To perform a base backup, use the following procedure.

Prerequisites

You must run the commands as the postgres superuser, a user with database administrator

privileges, or another user with at least REPLICATION permissions.

You must keep all the WAL segment files generated during and after the base backup.

Procedure

1. Use the pg_basebackup utility to perform the base backup.

To create a base backup as individual files (plain format):

$ pg_basebackup -D backup_directory -Fp

Replace backup_directory with your chosen backup location.

If you use tablespaces and perform the base backup on the same host as the server, you

must also use the --tablespace-mapping option, otherwise the backup will fail upon an

attempt to write the backup to the same location.

To create a base backup as a tar archive (tar and compressed format):

$ pg_basebackup -D backup_directory -Ft -z

Replace backup_directory with your chosen backup location.

To restore such data, you must manually extract the files in the correct locations.

2. After the base backup process is complete, safely archive the copy of the database cluster and

the WAL segment files used during the backup, which are specified in the backup history file.

3. Delete WAL segments numerically lower than the WAL segment files used in the base backup

because these are older than the base backup and no longer needed for a restore.

To specify which database server pg_basebackup will contact, use the following command-line options:

The -h option to define the host.

The default host is either the local host or a host specified by the PGHOST environment

variable.

The -p option to define the port.

The default port is indicated by the PGPORT environment variable or the compiled-in default.

Additional resources

PostgreSQL Documentation - base backup

PostgreSQL Documentation - pg_basebackup utility

4.5.3.5. Restoring the database using a continuous archive backup

To restore a database using a continuous backup, use the following procedure.

CHAPTER 4. USING POSTGRESQL

Procedure

1. Stop the server:

# systemctl stop postgresql.service

2. Copy the necessary data to a temporary location.

Preferably, copy the whole cluster data directory and any tablespaces. Note that this requires

enough free space on your system to hold two copies of your existing database.

If you do not have enough space, save the contents of the cluster’s pg_wal directory, which can

contain logs that were not archived before the system went down.

3. Remove all existing files and subdirectories under the cluster data directory and under the root

directories of any tablespaces you are using.

4. Restore the database files from your base backup.

Ensure that:

The files are restored with the correct ownership (the database system user, not root).

The files are restored with the correct permissions.

The symbolic links in the pg_tblspc/ subdirectory are restored correctly.

5. Remove any files present in the pg_wal/ subdirectory.

These files resulted from the base backup and are therefore obsolete. If you did not archive

pg_wal/, recreate it with proper permissions.

6. Copy any unarchived WAL segment files that you saved in step 2 into pg_wal/.

7. Create the recovery.conf recovery command file in the cluster data directory and specify the

shell command in the restore_command configuration parameter. You can use the cp

command, another command, or a shell script. For example:

restore_command = 'cp /mnt/server/archivedir/%f "%p"'

8. Start the server:

# systemctl start postgresql.service

The server will enter the recovery mode and proceed to read through the archived WAL files

that it needs.

If the recovery is terminated due to an external error, the server can be restarted and it will

continue the recovery. When the recovery process is completed, the server renames

recovery.conf to recovery.done. This prevents the server from accidental re-entering the

recovery mode after it starts normal database operations.

9. Check the contents of the database to verify that the database has recovered into the required

state.

If the database has not recovered into the required state, return to step 1. If the database has

recovered into the required state, allow the users to connect by restoring the client

authentication configuration in the pg_hba.conf file.

For more information about restoring using the continuous backup, see PostgreSQL Documentation.

Red Hat Enterprise Linux 9 Configuring and using database servers

4.5.3.6. Additional resources

Continuous archiving method

4.6. MIGRATING TO A RHEL 9 VERSION OF POSTGRESQL

Red Hat Enterprise Linux 8 provides PostgreSQL in multiple module streams: PostgreSQL 10 (the

default postgresql stream), PostgreSQL 9.6, PostgreSQL 12, PostgreSQL 13, PostgreSQL 15, and

PostgreSQL 16.

In RHEL 9, PostgreSQL 13, PostgreSQL 15, and PostgreSQL 16 are available.

On RHEL, you can use two PostgreSQL migration paths for the database files:

Fast upgrade using the pg_upgrade utility

Dump and restore upgrade

The fast upgrade method is quicker than the dump and restore process. However, in certain cases, the

fast upgrade does not work, and you can only use the dump and restore process, for example in case of

cross-architecture upgrades.

As a prerequisite for migration to a later version of PostgreSQL, back up all your PostgreSQL

databases.

Dumping the databases and performing backup of the SQL files is required for the dump and restore

process and recommended for the fast upgrade method.

Before migrating to a later version of PostgreSQL, see the upstream compatibility notes for the version

of PostgreSQL to which you want to migrate, and for all skipped PostgreSQL versions between the one

you are migrating from and the target version.

4.6.1. Notable differences between PostgreSQL 15 and PostgreSQL 16

PostgreSQL 16 introduced the following notable changes.

The postmasters binary is no longer available

PostgreSQL is no longer distributed with the postmaster binary. Users who start the postgresql server

by using the provided systemd unit file (the systemctl start postgres command) are not affected by

this change. If you previously started the postgresql server directly through the postmaster binary, you

must now use the postgres binary instead.

Documentation is no longer packaged

PostgreSQL no longer provides documentation in PDF format within the package. Use the online

documentation instead.

4.6.2. Notable differences between PostgreSQL 13 and PostgreSQL 15

PostgreSQL 15 introduced the following backwards incompatible changes.

Default permissions of the public schema

The default permissions of the public schema have been modified in PostgreSQL 15. Newly created

users need to grant permission explicitly by using the GRANT ALL ON SCHEMA public TO myuser;

command.

CHAPTER 4. USING POSTGRESQL

The following example works in PostgreSQL 13 and earlier:

postgres=# CREATE USER mydbuser;

postgres=# \c postgres mydbuser

postgres=$ CREATE TABLE mytable (id int);

The following example works in PostgreSQL 15 and later:

postgres=# CREATE USER mydbuser;

postgres=# GRANT ALL ON SCHEMA public TO mydbuser;

postgres=# \c postgres mydbuser

postgres=$ CREATE TABLE mytable (id int);

NOTE

Ensure that the mydbuser access is configured appropriately in the pg_hba.conf file.

See Creating PostgreSQL users for more information.

PQsendQuery() no longer supported in pipeline mode

Since PostgreSQL 15, the libpq PQsendQuery() function is no longer supported in pipeline mode.

Modify affected applications to use the PQsendQueryParams() function instead.

4.6.3. Fast upgrade using the pg_upgrade utility

As a system administrator, you can upgrade to the most recent version of PostgreSQL by using the fast

upgrade method. To perform a fast upgrade, copy binary data files to the /var/lib/pgsql/data/ directory

and use the pg_upgrade utility.

You can use this method for migrating data:

From the RHEL 8 version of PostgreSQL 12 to a RHEL version of PostgreSQL 13

From a RHEL 8 or 9 version of PostgreSQL 13 to a RHEL version of PostgreSQL 15

From a RHEL 8 or 9 version of PostgreSQL 15 to a RHEL version of PostgreSQL 16

The following procedure describes migration from the RHEL 8 version of PostgreSQL 12 to the RHEL 9

version of PostgreSQL 13 using the fast upgrade method. For migration from postgresql streams other

than 12, use one of the following approaches:

Update your PostgreSQL server to version 12 on RHEL 8 and then use the pg_upgrade utility

to perform the fast upgrade to RHEL 9 version of PostgreSQL 13.

Use the dump and restore upgrade directly between any RHEL 8 version of PostgreSQL and an

equal or later PostgreSQL version in RHEL 9.

Prerequisites

Before performing the upgrade, back up all your data stored in the PostgreSQL databases. By

default, all data is stored in the /var/lib/pgsql/data/ directory on both the RHEL 8 and RHEL 9

systems.

Procedure

Red Hat Enterprise Linux 9 Configuring and using database servers

1. On the RHEL 9 system, install the postgresql-server and postgresql-upgrade packages:

# dnf install postgresql-server postgresql-upgrade

Optionally, if you used any PostgreSQL server modules on RHEL 8, install them also on the

RHEL 9 system in two versions, compiled both against PostgreSQL 12 (installed as the

postgresql-upgrade package) and the target version of PostgreSQL 13 (installed as the

postgresql-server package). If you need to compile a third-party PostgreSQL server module,

build it both against the postgresql-devel and postgresql-upgrade-devel packages.

2. Check the following items:

Basic configuration: On the RHEL 9 system, check whether your server uses the default

/var/lib/pgsql/data directory and the database is correctly initialized and enabled. In

addition, the data files must be stored in the same path as mentioned in the

/usr/lib/systemd/system/postgresql.service file.

PostgreSQL servers: Your system can run multiple PostgreSQL servers. Ensure that the

data directories for all these servers are handled independently.

PostgreSQL server modules: Ensure that the PostgreSQL server modules that you used

on RHEL 8 are installed on your RHEL 9 system as well. Note that plugins are installed in the

/usr/lib64/pgsql/ directory.

3. Ensure that the postgresql service is not running on either of the source and target systems at

the time of copying data.

# systemctl stop postgresql.service

4. Copy the database files from the source location to the /var/lib/pgsql/data/ directory on the

RHEL 9 system.

5. Perform the upgrade process by running the following command as the PostgreSQL user:

# postgresql-setup --upgrade

This launches the pg_upgrade process in the background.

In case of failure, postgresql-setup provides an informative error message.

6. Copy the prior configuration from /var/lib/pgsql/data-old to the new cluster.

Note that the fast upgrade does not reuse the prior configuration in the newer data stack and

the configuration is generated from scratch. If you want to combine the old and new

configurations manually, use the *.conf files in the data directories.

7. Start the new PostgreSQL server:

# systemctl start postgresql.service

8. Analyze the new database cluster.

For PostgreSQL 13:

su postgres -c '~/analyze_new_cluster.sh'

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For PostgreSQL 15 or later:

su postgres -c 'vacuumdb --all --analyze-in-stages'

NOTE

You may need to use ALTER COLLATION name REFRESH VERSION, see

the upstream documentation for details.

9. If you want the new PostgreSQL server to be automatically started on boot, run:

# systemctl enable postgresql.service

4.6.4. Dump and restore upgrade

When using the dump and restore upgrade, you must dump all databases contents into an SQL file

dump file. Note that the dump and restore upgrade is slower than the fast upgrade method and it may

require some manual fixing in the generated SQL file.

You can use this method for migrating data from any RHEL 8 version of PostgreSQL to any equal or

later version of PostgreSQL in RHEL 9.

On RHEL 8 and RHEL 9 systems, PostgreSQL data is stored in the /var/lib/pgsql/data/ directory by

default.

To perform the dump and restore upgrade, change the user to root.

The following procedure describes migration from the RHEL 8 default version of PostgreSQL 10 to the

RHEL 9 version of PostgreSQL 13.

Procedure

1. On your RHEL 8 system, start the PostgreSQL 10 server:

# systemctl start postgresql.service

2. On the RHEL 8 system, dump all databases contents into the pgdump_file.sql file:

su - postgres -c "pg_dumpall > ~/pgdump_file.sql"

3. Ensure that the databases were dumped correctly:

su - postgres -c 'less "$HOME/pgdump_file.sql"'

As a result, the path to the dumped sql file is displayed: /var/lib/pgsql/pgdump_file.sql.

4. On the RHEL 9 system, install the postgresql-server package:

# dnf install postgresql-server

Optionally, if you used any PostgreSQL server modules on RHEL 8, install them also on the

RHEL 9 system. If you need to compile a third-party PostgreSQL server module, build it against

the postgresql-devel package.

Red Hat Enterprise Linux 9 Configuring and using database servers

5. On the RHEL 9 system, initialize the data directory for the new PostgreSQL server:

# postgresql-setup --initdb

6. On the RHEL 9 system, copy the pgdump_file.sql into the PostgreSQL home directory, and

check that the file was copied correctly:

su - postgres -c 'test -e "$HOME/pgdump_file.sql" && echo exists'

7. Copy the configuration files from the RHEL 8 system:

su - postgres -c 'ls -1 $PGDATA/*.conf'

The configuration files to be copied are:

/var/lib/pgsql/data/pg_hba.conf

/var/lib/pgsql/data/pg_ident.conf

/var/lib/pgsql/data/postgresql.conf

8. On the RHEL 9 system, start the new PostgreSQL server:

# systemctl start postgresql.service

9. On the RHEL 9 system, import data from the dumped sql file:

su - postgres -c 'psql -f ~/pgdump_file.sql postgres'

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