Re: BUG #19502: unix_socket_group doesn't work anymore

The following bug has been logged on the website:

Bug reference: 19502
Logged by: Pierre Juhen
Email address:pierre.juhen@orange.fr
PostgreSQL version: 16.3
Operating system: Linux
Description:

Hi,

I developped an application on Alma Linux 9 and PostgreSQL 13.

I want to maintain it up to date, and try to "port" it to Alma Linux 10 and
PostgreSQL 16.13

Previously the appplication run under the identity of a plain user. The Unix
socket (/var/run/postgresql/.s.PGSQL.5432) was owned by postgres and the
group was that plain user one.

Now, postgreSQL refuses to launch with the following error :

2026-05-30 23:59:27.178 CEST [5163] LOG: n'a pas pu initialiser le groupe
du fichier « /var/run/postgresql/.s.PGSQL.5432 » : Opération non permise
2026-05-30 23:59:27.178 CEST [5163] ATTENTION: n'a pas pu créer la socket
de domaine Unix dans le répertoire « /var/run/postgresql »
2026-05-30 23:59:27.180 CEST [5163] LOG: n'a pas pu initialiser le groupe
du fichier « /tmp/.s.PGSQL.5432 » : Opération non permise
2026-05-30 23:59:27.180 CEST [5163] ATTENTION: n'a pas pu créer la socket
de domaine Unix dans le répertoire « /tmp »
2026-05-30 23:59:27.180 CEST [5163] FATAL: n'a pas pu créer les sockets de
domaine Unix

Translated by google in english :

2026-05-30 23:59:27.178 CEST [5163] LOG: Could not initialize the group for
the file '/var/run/postgresql/.s.PGSQL.5432': Operation not permitted
2026-05-30 23:59:27.178 CEST [5163] WARNING: Could not create the Unix
domain socket in the directory '/var/run/postgresql'
2026-05-30 23:59:27.180 CEST [5163] LOG: Could not initialize the group for
the file '/tmp/.s.PGSQL.5432': Operation not permitted
2026-05-30 23:59:27.180 CEST [5163] WARNING: Could not create the socket
Unix domain in the "/tmp" directory
2026-05-30 23:59:27.180 CEST [5163] FATAL: Could not create Unix domain
sockets

If I comment unix_socket_group in postgresql.conf, the system starts without
any problem.

The postgres heading process has got the right chown capability (cap_chown)

I don't undestand what append.

The same problem occurs with my development machine (Fedora 44 and and
PostgreSQL 18.3).

Recent changes in the kernel ?

Any help would be welcome.

Thanks,

Pierre