error with postgresql datababse : Is the server running locally and accepting connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"?

The convention for PostgreSQL packaged for Debian or Debian derivatives such as Ubuntu is to use /var/run/postgresql as the directory for Unix domain sockets. On the other hand the convention for self-compiled postgres client libs is to use /tmp, unless self-configured otherwise.

So the usual root cause of this mismatch between both is a mix of self-compiled client-side stuff with pre-compiled server-side packages (even if client and server are installed on the same machine, client-side and server-side are still distinct and can be out of sync).

Soft-linking from /tmp to this directory as suggested by the asker works except that the link will be lost at every reboot, because in general /tmp is emptied on reboot.

A better option would be to add as an entry in database.yml:

• either host: /tmp if the real socket path is /tmp (self-compiled server, packaged client)

• or host: /var/run/postgresql if the real socket path /var/run/postgresql/ (packaged server, self-compiled client).

When the value in the host field starts with a slash character, the postgres library knows that it's the location of a directory for local sockets rather than a hostname. The filename inside the directory .s.PGSQL.portnumber is generated and must not be specified, only the directory.

Another possibility is to configure the self-compiled software packages as closely as possible to Debian, overriding the defaults as they do.

I had the same Is the server running locally and accepting connections on Unix domain socket “/var/run/postgresql/.s.PGSQL.5432”? error when typing psql into the postgres user in Ubuntu 14.04. I could not find an existing working solution.

The short answer for me was: my install made a var/pgsql_socket directory but no configuration files knew about it.

1) Find the postgres.conf file (it was in etc/postgresql/9.6/main for me)
2) change to listen_addresses = '*'
3) add another unix socket directory
unix_socket_directories = '/var/run/postgresql, /var/pgsql_socket' # comma-separated list of directories
4) at this point, sudo service postgresql start attempted to start but did not have authority to create the lock file.
* The PostgreSQL server failed to start. Please check the log output: 2016-10-05 17:14:55 CEST [28472-1] FATAL: could not create lock file "/var/pgsql_socket/.s.PGSQL.5432.lock": Permission denied 2016-10-05 17:14:55 CEST [28472-2] LOG: database system is shut down
5) Change permissions ( found from Mark Berry's comment here )
$ sudo chown root.postgres /var/pgsql_socket
$ sudo chmod g+wx /var/pgsql_socket
6) sudo service postgresql start
sudo -i -u postgres
psql

That finally worked for me

I solved It . I Just created a softlink using :

sudo ln -s /tmp/.s.PGSQL.5432 /var/run/postgresql/.s.PGSQL.5432

and then edited the

/etc/postgresql/9.4/main/pg_hba.conf

( If you have another version of postgresql you have to change 9.4 in the path)

From:

local all postgres peer

To:

local all postgres md5