[root@centos9-stream ~]# locale
LANG=en_US.UTF-8
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

[root@centos9-stream ~]# rpm -qa |grep postgres
postgresql-private-libs-13.16-1.el9.x86_64
postgresql-13.16-1.el9.x86_64
postgresql-server-13.16-1.el9.x86_64

[root@centos9-stream ~]# postgresql-setup --initdb
 * Initializing database in '/var/lib/pgsql/data'
 * Initialized, logs are in /var/lib/pgsql/initdb_postgresql.log
[root@centos9-stream ~]# systemctl start postgresql
[root@centos9-stream ~]# su - postgres
[postgres@centos9-stream ~]$ psql --list
                                  List of databases
   Name    |  Owner   | Encoding |   Collate   |    Ctype    |   Access privileges   
-----------+----------+----------+-------------+-------------+-----------------------
 postgres  | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | 
 template0 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.UTF-8 | en_US.UTF-8 | =c/postgres          +
           |          |          |             |             | postgres=CTc/postgres
(3 rows)

[root@centos9-stream ~] echo 'LANG="en_GB.UTF-8"' > /etc/locale.conf
<relogin dance>

[root@centos9-stream ~]# locale
LANG=en_GB.UTF-8
LC_CTYPE="en_GB.UTF-8"
LC_NUMERIC="en_GB.UTF-8"
LC_TIME="en_GB.UTF-8"
LC_COLLATE="en_GB.UTF-8"
LC_MONETARY="en_GB.UTF-8"
LC_MESSAGES="en_GB.UTF-8"
LC_PAPER="en_GB.UTF-8"
LC_NAME="en_GB.UTF-8"
LC_ADDRESS="en_GB.UTF-8"
LC_TELEPHONE="en_GB.UTF-8"
LC_MEASUREMENT="en_GB.UTF-8"
LC_IDENTIFICATION="en_GB.UTF-8"
LC_ALL=

[root@centos9-stream ~]# dnf module enable postgresql:15
[root@centos9-stream ~]# dnf upgrade
[root@centos9-stream ~]# dnf install postgresql-upgrade

[root@centos9-stream ~]# rpm -qa |grep postgres
postgresql-private-libs-15.8-2.module_el9+1108+b05fe5f3.x86_64
postgresql-15.8-2.module_el9+1108+b05fe5f3.x86_64
postgresql-server-15.8-2.module_el9+1108+b05fe5f3.x86_64
postgresql-upgrade-15.8-2.module_el9+1108+b05fe5f3.x86_64


[root@centos9-stream ~]# postgresql-setup --upgrade
 * Upgrading database.
ERROR: pg_upgrade tool failed
ERROR: Upgrade failed.
 * See /var/lib/pgsql/upgrade_postgresql.log for details.

[root@centos9-stream ~]# cat /var/lib/pgsql/upgrade_postgresql.log
Performing Consistency Checks
-----------------------------
Checking cluster versions                                   ok
Checking database user is the install user                  ok
Checking database connection settings                       ok
Checking for prepared transactions                          ok
Checking for system-defined composite types in user tables  ok
Checking for reg* data types in user tables                 ok
Checking for contrib/isn with bigint-passing mismatch       ok
Checking for user-defined encoding conversions              ok
Checking for user-defined postfix operators                 ok
Checking for incompatible polymorphic functions             ok
Creating dump of global objects                             ok
Creating dump of database schemas                           ok

lc_collate values for database "template1" do not match:  old "en_US.UTF-8", new "en_GB.UTF-8"
Failure, exiting