From: Tom Lane <tgl@sss.pgh.pa.us>
To: pavan95 <pavan.postgresdba@gmail.com>
cc: pgsql-admin@postgresql.org
Subject: Re: Error when starting postgres database!!
In-reply-to: <1539058967018-0.post@n3.nabble.com>
References: <1539058967018-0.post@n3.nabble.com>
Comments: In-reply-to pavan95 <pavan.postgresdba@gmail.com>
	message dated "Mon, 08 Oct 2018 21:22:47 -0700"
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Date: Tue, 09 Oct 2018 00:38:21 -0400
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pavan95 <pavan.postgresdba@gmail.com> writes:
> I'm facing an error in starting my postgresql database. The error is as
> shown below:

> bash-4.1$ 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"?

Note the error message: it mentions the Unix socket location
"/var/run/postgresql/.s.PGSQL.5432".  This means the psql (or
more precisely, libpq.so) that you're using thinks that PG
socket files live in /var/run/postgresql.  That is *not* standard;
as shipped by the community, PG puts its socket files in "/tmp".
However, various distros think that is bad style and override
the build option to put the socket files elsewhere, most often
/var/run/postgresql.

In short, you are probably using a vendor-supplied libpq to
try to talk to a PG server that was built from unmodified
community code.  You could confirm the latter by looking to see
if there's a /tmp/.s.PGSQL.5432 socket file.

You could use "psql -h /tmp" to override libpq's idea of the
socket location, or use "psql -h localhost" to forget about
socket files and connect via TCP, or change the server's
unix_socket_directories parameter to make it create a socket
(or additional socket) in /var/run/postgresql, or replace
either your libpq or your server with something that's got
the same built-in default location as the other end.

			regards, tom lane