Re: [GENERAL] psql - looking in wrong place for socket

On 03/17/2017 06:42 AM, Steve Clark wrote:

Hi List,

I am running postgresql 8.4.20 on CentOS 6. Things have been running fine for a long time
then I rebooted. Postgres came up but when I tried to connect with psql on the local machine
I got

psql: could not connect to server: No such file or directory       Is the server running locally and accepting       connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

The socket is actually being created (and always has been) in /tmp

So you built Postgres from source?

No - it is installed using yum.

It looks like the problem is someone loaded postgresql-9.5 and psql was using:
psql    14971 postgres  mem    REG                8,4   193296   950807 /usr/pgsql-9.5/lib/libpq.so.5.8

the libpq from 9.5.

By removing the ln and using

# rm /var/run/postgresql/.s.PGSQL.5432
rm: remove symbolic link `/var/run/postgresql/.s.PGSQL.5432'? y

$ psql
psql: could not connect to server: No such file or directory
        Is the server running locally and accepting
        connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

$ LD_LIBRARY_PATH=/usr/lib64 psql
psql (8.4.20)
Type "help" for help.

postgres=#

It works OK again.

So now I know what caused the problem.

Thanks,
Steve

I worked around the problem temporarily by
ln -s /tmp/.s.PGSQL.5432 /var/run/postgresql/.s.PGSQL.5432

What controls where psql looks for the socket?

https://www.postgresql.org/message-id/23876.1488949292%40sss.pgh.pa.us

"With the default configure options you used, the postmaster would have 
put its Unix socket file into /tmp, not /var/run.  I wonder whether your
problem is that you're trying to connect to it with distro-supplied
psql+libpq that expects to find the Unix socket in /var/run."

Thanks,
Steve