Psql could not connect to server: No such file or directory, 5432 error?

Question

I'm trying to run psql on my Vagrant machine, but I get this error:

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: Vagrant 1.9.2 Box: ubuntu/trusty64, https://atlas.hashicorp.com/ubuntu/boxes/trusty64

EDIT Commands I've used in order to install and run postgres:

• sudo apt-get update
• sudo apt-get install postgresql
• sudo su postgres
• psql -d postgres -U postgres

Answer 1

I've had this same issue, related to the configuration of my pg_hba.conf file (located in /etc/postgresql/9.6/main). Please note that 9.6 is the postgresql version I am using.

The error itself is related to a misconfiguration of postgresql, which causes the server to crash before it starts.

I would suggest following these instructions:

1. Certify that postgresql service is running, using sudo service postgresql start
2. Run pg_lsclusters from your terminal

3. Check what is the cluster you are running, the output should be something like:

   Version - Cluster Port Status Owner Data directory

   9.6 ------- main -- 5432 online postgres /var/lib/postgresql/9.6/main

   Disregard the '---' signs, as they are being used there only for alignment. The important information are the version and the cluster. You can also check whether the server is running or not in the status column.

4. Copy the info from the version and the cluster, and use like so: pg_ctlcluster <version> <cluster> start, so in my case, using version 9.6 and cluster 'main', it would be pg_ctlcluster 9.6 main start
5. If something is wrong, then postgresql will generate a log, that can be accessed on /var/log/postgresql/postgresql-<version>-main.log, so in my case, the full command would be sudo nano /var/log/postgresql/postgresql-9.6-main.log.
6. The output should show what is the error.

   2017-07-13 16:53:04 BRT [32176-1] LOG: invalid authentication method "all"
   2017-07-13 16:53:04 BRT [32176-2] CONTEXT: line 90 of configuration file "/etc/postgresql/9.5/main/pg_hba.conf"
   2017-07-13 16:53:04 BRT [32176-3] FATAL: could not load pg_hba.conf

7. Fix the errors and restart postgresql service through sudo service postgresql restart and it should be fine.

I have searched a lot to find this, credit goes to this post.

Best of luck!