How to grant access to /var/run to postgres on CentOS?

Question

After installing postgres-9.3 via yum in my CentOS 7, its default configuration puts socket in /tmp directory. I have httpd (installed via yum as well) which is by default managed by system.d with PrivateTmp option enabled. This means that any web application running on httpd can't access /tmp so connect to postgres. I have changed postgres configuration so it should put its socket in /var/run/postgres just like in Ubuntu.

Now the problem is, that postgres doesn't have enough privileges to write to /var/run. My first though was to do just:

chown postgres:postgres /var/run/postgres

But /var/run directory is cleaned after reboot so this won't work. My question is:

How to grant access to /var/run/postgres for postgres user in such a way that will persist reboots? I don't want to change socket location and I don't want to change httpd's system.d configuration. I just want postgres to be able to write to /var/run/postgres. Any help is much appreciated.

Answer 1

Are you sure the socket is only in /tmp on CentOS 7?

Recent versions of Fedora have two copies of the socket, one in /run/postgresql (which is where /var/run/postgresql is really located after links are resolved) which is the preferred version on modern systems, and one in /tmp for legacy clients that expect to find it there.

In any case if you do need to ensure the directory is created at boot then use a tmpfiles.d file, like /usr/lib/tmpfiles.d/postgresql.conf which ships in Fedora and contains:

d /var/run/postgresql 0755 postgres postgres -

Answer 2

The directory /var/run is a symbolic link to /run in CentOS 7. The socket directory for PostgreSQL is /run/postgresql. It is a temporary directory, created at boot time.

With the advent of systemd, a new mechanism called systemd-tmpfiles has been introduced to manage temporary files and directories.

Systemd-tmpfiles creates temporary directories during boot and sets their owner, group and permissions. CentOS 7 has the systemd-tmpfiles configuration for PostgreSQL in /usr/lib/tmpfiles.d/postgresql-96.conf. By default, the file contains the following line:

d /run/postgresql 0755 postgres postgres -

You can change permissions, owner and group by editing that line. The recommended way to make such changes, however, is not to directly edit files under /usr/lib/tmpfiles.d/, but to copy configuration files over to /etc/tmpfiles.d/, and make the necessary changes in that copy instead.

Answer 3

Just put your desired commands in /etc/rc.local file, and they will be executed at the end of each booting process.