AlmaLinux 9: choosing a PostgreSQL version and initialising it

Test scope

In an AlmaLinux 9.8 privileged container: dnf module list postgresql, --downloadonly version comparisons, initdb, pg_ctl, psql and pg_hba.conf. Log: plans/content-expansion/evidence/logs/alma-postgresql-install.log.

Initialisation was executed on 13.23; 16.x follows the same flow but was not run separately. The postgresql-setup / systemctl path depends on systemd and was not verified in the container.

Two sources: non-modular 13 and module streams

dnf module list postgresql
dnf -y install --downloadonly --destdir=/tmp/a postgresql-server
ls /tmp/a | grep '^postgresql-server'

postgresql 15  client, server [d]
postgresql 16  client, server [d]
postgresql 18  client, server [d]

postgresql-server-13.23-6.el9_8.x86_64.rpm

The module list shows 15/16/18, yet a plain install resolves 13.23: appstream also carries a non-modular 13, which dnf uses while no stream is enabled. That is EL9 packaging, not a bug.

Choose the version explicitly

sudo dnf module enable postgresql:16
sudo dnf -y install --downloadonly --destdir=/tmp/b postgresql-server
ls /tmp/b | grep '^postgresql-server'

postgresql-server-16.15-1.module+el9.8.0+40320+f6f9ed3c.x86_64.rpm

Only the module+el9.8.0 build comes from the stream. Enable, install, then confirm with rpm -q — do not skip any of the three.

Initialise: initdb in a container

sudo mkdir -p /var/lib/pgsql/data /var/run/postgresql
sudo chown -R postgres:postgres /var/lib/pgsql /var/run/postgresql
sudo -u postgres /usr/bin/initdb -D /var/lib/pgsql/data \
  --auth-local=trust --auth-host=scram-sha-256
cat /var/lib/pgsql/data/PG_VERSION

syncing data to disk ... ok
13

PG_VERSION records the major version; it is a more direct check than reading package names.

Start, connect and authenticate

sudo -u postgres /usr/bin/pg_ctl -D /var/lib/pgsql/data \
  -l /var/lib/pgsql/data/startup.log -o '-k /var/run/postgresql' start
sudo -u postgres psql -h /var/run/postgresql -tAc 'select version();'
grep -vE '^#|^$' /var/lib/pgsql/data/pg_hba.conf

PostgreSQL 13.23 on x86_64-redhat-linux-gnu, ...
local   all   all                     trust
host    all   all   127.0.0.1/32      scram-sha-256
host    all   all   ::1/128           scram-sha-256

The standard path on a real host

sudo dnf module enable postgresql:16
sudo dnf -y install postgresql-server
sudo postgresql-setup --initdb
sudo systemctl enable --now postgresql
psql --version

postgresql-setup initialises the cluster and registers the systemd unit; in a container it fails with System has not been booted with systemd, hence initdb there.

Common traps

Skipping module enable: you get 13 while the application assumes 16;
No /var/run/postgresql: local socket connections fail;
Mixing module streams with PGDG: two sources for one major overwrite each other during upgrades.

Practice: from version choice to a working connection

dnf module list postgresql
sudo dnf module enable postgresql:16
sudo dnf -y install postgresql-server
rpm -q postgresql-server | grep module
sudo postgresql-setup --initdb
sudo systemctl enable --now postgresql
sudo -u postgres psql -tAc 'select version();'

Checks:

rpm -q output contains module
systemctl is-active postgresql is active
select version() reports 16.x
cat PG_VERSION is 16

FAQ

常见问题

Why install 13 when the module list shows 15/16/18?

AppStream also ships a non-modular postgresql 13; without an enabled stream dnf resolves that package. Enable postgresql:16 first to get 16.

How do I confirm the version I wanted?

Three checks: `rpm -q postgresql-server` for `module` in the release, `cat /var/lib/pgsql/data/PG_VERSION` for the initialised major, and `psql -c "select version();"` for the running version.