socket should either be a link or mapped out to /socket/postgresql .....
root@postgresql:/# ls -l /var/run/
total 0
drwxr-x---. 2 Debian-exim Debian-exim 6 May 5 08:44 exim4
drwxrwxrwt. 2 root root 6 Apr 22 00:00 lock
drwxrwsr-x. 3 postgres postgres 99 May 5 10:01 postgresql
drwxr-xr-x. 3 root root 60 May 5 10:01 secrets
-rw-rw-r--. 1 root utmp 0 Apr 22 00:00 utmp