Xrhrft

The problem can also be attributed to a crashed process that left postmaster.pid file behind.

$ brew services stop postgresql

$ rm /usr/local/var/postgres/postmaster.pid # adjust path accordingly to your install

$ brew services start postgresql

I've just resolved the same problem. It's just because I forgot to run it properly before use.

For pure installing postgresql on Mac OS, the process will be (using brew command):

brew install postgresql

then if you want to automatically run postgresql at login:

ln -sfv /usr/local/opt/postgresql/*.plist ~/Library/LaunchAgents

or else you just want to run it anytime you want:

postgres -D /usr/local/var/postgres

If your case is more complicated, let's brew uninstall postgresql and redo these steps.

Hope it helps!

I was getting the same

Is the server running locally and accepting connections on Unix domain 

socket "/tmp/.s.PGSQL.5432"?

loop of Homebrew install / start / stop / restart to no avail...

Finally, brew postgresql-upgrade-database worked.

Seems I was on 9.6 instead of 10.4, and something my latest App Store restart restarted all my database servers...

psql: could not connect to server: No such file or directory

    Is the server running locally and accepting

    connections on Unix domain socket"/var/pgsql_socket/.s.PGSQL.5432"?

I kept on getting the above error and none of the above solutions worked for me. Finally the following solution solved my problem on Mac OS X

Install postgres using brew

brew install postgres

Install brew services

brew tap homebrew/services

To start postgres as a background service

brew services start postgresql

To stop postgres manually

brew services stop postgresql

We can also use brew services to restart Postgres

brew services restart postgresql

I just uncomment in /etc/postgresql/9.5/main/postgresql.conf

unix_socket_permissions = 0777

and restart postgres.
And for me it works.

recently I went thru a similar problem. there's just another problem and solution. I was running 2 version of postgres (9.3 and 9.6) although the server was set to run on 2 different port but some how the psql command on bash try to connect to default port 5432.
Make sure to check if your server is running and check your port settings, then run psql -p <port> postgres.
The solution is changing port.

This happens when postgres server is not running.
Steps to properly install Postgres via Homebrew on MAC :

1. brew install postgres




2. initdb /Users/<username>/db -E utf8
   [This initializes postgres to use the given directory as the database directory. Normally it is not adviced to use the user directory for database storage. Edit sudoers file to add initdb and similar commands and then run initdb on /usr/local/var/postgres]




3. pg_ctl -D /Users/<username>/db -l logfile start
   [After getting success with step 2 it will prompt to run step 3. This command manually starts the server.]

I was looking for a long time, and this was the most clean and neat solution:

I recently upgraded Postgres from 9.2 to 9.3 using brew upgrade postgres. The process was smooth and pg_upgrade is a very handy tool.

However, trouble struck once I tried to run any specs that needed to connect to Postgres. Even though Postgres was definitely running, suddenly I was getting:

could not connect to server: No such file or directory (PG::ConnectionBad)
Is the server running locally and accepting
connections on Unix domain socket "/var/pgsql_socket/.s.PGSQL.5432"?
The problem was that the new version of Postgres listens on /tmp/.s.PGSQL.5432 instead. I could’ve messed around with the config and made Postgres use the domain socket it was previously, or told Rails explictly how to connect, but both of those approaches seemed like work I shouldn’t have to do. At no point had I told Rails to connect to postgres on that path, Rails had assumed it, and now its assumptions were wrong.

The fix is simple, if a little suprising. When you install the ‘pg’ gem, it detects which version of Postgres is installed and sets the domain socket path appropriately. The solution is as simple as reinstalling the gem.

$ gem uninstall pg
$ cd my-rails-app/
$ bundle install


http://daniel.fone.net.nz/blog/2014/12/01/fixing-connection-errors-after-upgrading-postgres/

It worked for me.
Change your postgresql directory according to version in your system.

Common path-
rm /usr/local/var/postgres/postmaster.pid

but for postgresql@9.6 in my system path is
rm /usr/local/var/postgresql@9.6/postmaster.pid

restart postgresql@9.6-
brew services restart postgresql@9.6

The steps below helps me:

brew uninstall postgresql
brew install postgresql
brew postgresql-upgrade-database