psql : connections on Unix domain socket "/var/run/postgresql/.s.PGSQL.5432"? - postgresql

Question

I have installed postgresql and done all the setup and created db and tables yesterday but today morning I got sudden this error
I have also uninstalled and installed postgresql but still same error. And also I have observed that when installed freshly it is working fine but once I shutdown or restart my system I'm getting the below 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"?
I have tried all the solutions given in all the mediums but I'm not able to resolve the issue so I'm posting this question again with my outputs.
The status of postgresql
**sudo /etc/init.d/postgresql status**
postgresql.service - PostgreSQL RDBMS
Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled)
Active: active (exited) since Wed 2019-10-30 11:40:39 IST; 5min ago
Process: 7666 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
Main PID: 7666 (code=exited, status=0/SUCCESS)
Tasks: 0
Memory: 0B
CPU: 0
CGroup: /system.slice/postgresql.service
When I run the pg_lsclusters
**pg_lsclusters**
Ver Cluster Port Status Owner Data directory Log file
11 main 5432 down postgres /var/lib/postgresql/11/main /var/log/postgresql/postgresql-11-main.log
**dpkg -l | grep postgres**
ii pgdg-keyring 2018.2 all keyring for apt.postgresql.org
ii postgresql 11+207.pgdg16.04+1 all object-relational SQL database (supported version)
ii postgresql-11 11.5-3.pgdg16.04+1 amd64 object-relational SQL database, version 11 server
ii postgresql-client-11 11.5-3.pgdg16.04+1 amd64 front-end programs for PostgreSQL 11
ii postgresql-client-common 207.pgdg16.04+1 all manager for multiple PostgreSQL client versions
ii postgresql-common 207.pgdg16.04+1 all PostgreSQL database-cluster manager
ii postgresql-contrib 11+207.pgdg16.04+1 all additional facilities for PostgreSQL (supported version)
I even tried to restart the postgres still same issue.
**sudo /etc/init.d/postgresql status**

Answer 1

I had exactly this error message, and this is how I resolved it.
In the log file at /var/log/postgresql/postgresql-13-main.log, these lines were present:
2021-09-15 08:26:04.936 UTC [46258] LOG: invalid value for parameter "lc_messages": "en_US.UTF-8"
2021-09-15 08:26:04.936 UTC [46258] LOG: invalid value for parameter "lc_monetary": "en_US.UTF-8"
2021-09-15 08:26:04.937 UTC [46258] LOG: invalid value for parameter "lc_numeric": "en_US.UTF-8"
2021-09-15 08:26:04.937 UTC [46258] LOG: invalid value for parameter "lc_time": "en_US.UTF-8"
2021-09-15 08:26:04.937 UTC [46258] FATAL: configuration file "/etc/postgresql/13/main/postgresql.conf" contains errors
pg_ctl: could not start server
Examine the log output.
This is caused by missing locales, with these possible fixes:
localedef allegedly fixes this according but I had no luck with this.
localedef -i en_US -f UTF-8 en_US.UTF-8
change postgresql.conf and use a locale that does exist (en_GB in my case)
lc_messages = 'en_GB.UTF-8' # locale for system error message strings
lc_monetary = 'en_GB.UTF-8' # locale for monetary formatting
lc_numeric = 'en_GB.UTF-8' # locale for number formatting
lc_time = 'en_GB.UTF-8' # locale for time formatting
post settings
port = 5432 # (change requires restart)
Port was wrong on my PostgreSQL 13 default config (was 5433) and required a change back to the default 5432. I presume this was a result of upgrading from v11 so it gave it a new port number.
After these changes, PostgreSQL needs to restart and it should now function correctly without errors in the log, and the psql command working as expected.

Answer 2

Try this:
sudo -u postgres -i
And then:
initdb --locale $LANG -E UTF8 -D '/var/lib/postgres/data/'
exit
This has worked for me so far