PostgreSQL Error Handling

Psql: Cannot join to server: No file or directory
Whether the server is running locally and is in a Unix domain socket
Ready to accept joins on "/var/run/postgresql/.s.pgsql.5432"?

[email protected]:/$ sudo service PostgreSQL start
Failed to start Postgresql.service:Unit Postgresql.service is masked.
[Email protected]:/$ sudo systemctl unmask postgresql
Removed Symlink/etc/systemd/system/postgresql.service.

[email  protected]:/$ sudo systemctl restart PostgreSQL
[email protected]:/$ sudo Service PostgreSQL start
[email protected]:/$ service PostgreSQL status
Postgresql.service-postgresql RDBMS
loaded:loaded (/lib/systemd/system/postgresql.service; enabled; vendor preset:enabled)
Active:active (exited) since three 2017-04-05 23:40:24 CST; 20s ago
process:9895 Execstart=/bin/tru E (code=exited, status=0/success)
Main pid:9895 (code=exited, status=0/success)

April 23:40:24 DONGYANG-K46CB systemd[1]: Starting PostgreSQL RDBMS ...
April 23:40:24 DONGYANG-K46CB systemd[1]: Started PostgreSQL RDBMS.
April 23:40:37 DONGYANG-K46CB systemd[1]: Started PostgreSQL RDBMS.

PostgreSQL Error Handling