PostgreSQL is available on RHEL/Cent OS by default as AppStream. As per RHEL documentation, RHEL/CentOS comes with a new feature called Application Streams (AppStreams), in which multiple versions of packages are provided, with a known period of support.

These modules can be thought of as package groups that represent an application, a set of tools, or runtime languages.

We can see the list of modules available modules to us after a fresh installation of RHEL 9 using the below command

yum module list

How to install default version of PostgreSQL using AppStream?

RHEL/Cent OS 9 provides PostgreSQL 13 as the initial version of this Application Stream, which can be installed with

dnf install postgresql-server

[root@pghelp01 ~]# dnf install postgresql-server
Last metadata expiration check: 0:13:17 ago on Saturday 06 April 2024 07:06:21 PM.
Dependencies resolved.
=======================================================================================================================================
Package Architecture Version Repository Size
=======================================================================================================================================
Installing:
postgresql-server x86_64 13.14-1.el9 appstream 5.8 M
Installing dependencies:
postgresql x86_64 13.14-1.el9 appstream 1.6 M
postgresql-private-libs x86_64 13.14-1.el9 appstream 133 k

Transaction Summary
=======================================================================================================================================
Install 3 Packages

Total download size: 7.5 M
Installed size: 29 M
Is this ok [y/N]:

Additional PostgreSQL versions are provided as modules with a shorter life cycle in minor releases of RHEL 9/Cent OS 9. To see the list of modules run the below command

dnf module list postgresql

[root@pghelp01 ~]# dnf module list postgresql
Last metadata expiration check: 0:12:55 ago on Saturday 06 April 2024 07:06:21 PM.
CentOS Stream 9 - AppStream
Name Stream Profiles Summary
postgresql 15 [x] client, server [d] PostgreSQL server and client module
postgresql 16 [x] client, server [d] PostgreSQL server and client module

Hint: [d]efault, [e]nabled, [x]disabled, [i]nstalled

You can notice both postgresql 15 and postgresql 16 are disabled [x] under Stream.

Before installing any module, let’s understand how to install a module in Cent OS 9.

Here is an example that we can break down to show all the options.

# dnf module install module:version/profile

• module defines which module we are going to install.

• :version specifies which stream we are going to use for the specified module.

• /profile tells us which profile to use. If no profile is specified, the default one is used. As per the above example., server is the default module.

How to install user specified version of PostgreSQL using AppStream?

To install PostgreSQL 16, for example., run the below command

dnf module install postgresql:16

To install PostgreSQL 16 client run the below command

dnf module install postgresql:16/client

How to make PostgreSQL 16 as the default version of module installation?

List the available module

[root@pghelp01 ~]# dnf module list postgresql
Last metadata expiration check: 0:32:20 ago on Saturday 06 April 2024 07:06:21 PM.
CentOS Stream 9 - AppStream
Name Stream Profiles Summary
postgresql 15 [x] client, server [d] PostgreSQL server and client module
postgresql 16 [x] client, server [d] PostgreSQL server and client module

Hint: [d]efault, [e]nabled, [x]disabled, [i]nstalled

Enable PostgreSQL 16 module

[root@pghelp01 ~]# dnf module enable postgresql:16
Last metadata expiration check: 0:32:29 ago on Saturday 06 April 2024 07:06:21 PM.
Dependencies resolved.
=======================================================================================================================================
 Package                         Architecture                   Version                          Repository                       Size
=======================================================================================================================================
Enabling module streams:
 postgresql                                                     16

Transaction Summary
=======================================================================================================================================

Is this ok [y/N]: y
Complete!
[root@pghelp01 ~]#

Check again to notice [e] for Version 16 under stream 

[root@pghelp01 ~]# dnf module list postgresql
Last metadata expiration check: 0:32:35 ago on Saturday 06 April 2024 07:06:21 PM.
CentOS Stream 9 - AppStream
Name                       Stream                 Profiles                           Summary
postgresql                 15                     client, server [d]                 PostgreSQL server and client module
postgresql                 16 [e]                 client, server [d]                 PostgreSQL server and client module

Hint: [d]efault, [e]nabled, [x]disabled, [i]nstalled

Putting everything together to install PostgreSQL 16 and initializing PostgreSQL on Cent OS 9

Install the PostgreSQL server packages:

dnf install postgresql-server

Initialize the database cluster:

postgresql-setup --initdb

Start the postgresql service:

systemctl start postgresql.service

Enable the postgresql service to start at boot:

systemctl enable postgresql.service

Check the current status of the service

systemctl status postgresql.service

[root@pghelp01 ~]# systemctl status postgresql.service
● postgresql.service - PostgreSQL database server
     Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; preset: disabled)
     Active: active (running) since Sat 2024-04-06 19:43:00 IST; 10s ago
   Main PID: 3774 (postgres)
      Tasks: 7 (limit: 22817)
     Memory: 17.5M
        CPU: 41ms
     CGroup: /system.slice/postgresql.service
             ├─3774 /usr/bin/postgres -D /var/lib/pgsql/data
             ├─3775 "postgres: logger "
             ├─3776 "postgres: checkpointer "
             ├─3777 "postgres: background writer "
             ├─3779 "postgres: walwriter "
             ├─3780 "postgres: autovacuum launcher "
             └─3781 "postgres: logical replication launcher "

Apr 06 19:43:00 pghelp01 systemd[1]: Starting PostgreSQL database server...
Apr 06 19:43:00 pghelp01 postgres[3774]: 2024-04-06 19:43:00.967 IST [3774] LOG:  redirecting log output to logging collector process
Apr 06 19:43:00 pghelp01 postgres[3774]: 2024-04-06 19:43:00.967 IST [3774] HINT:  Future log output will appear in directory "log".
Apr 06 19:43:00 pghelp01 systemd[1]: Started PostgreSQL database server.

If the installation is from PostgreSQL repository, the installation should look like this

More details can be found here

Words from postgreshelp

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