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How to Fix psql: error: could not connect to server: No such file or directory in PostgreSQL

 

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

-bash-4.2$ psql

psql: error: 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"?

-bash-4.2$

Check wheather postgres cluster is running or not using below comand 

-bash-4.2$ ps -ef | grep -i postgres

root      3318  3253  0 06:05 pts/0    00:00:00 sudo su - postgres

root      3319  3318  0 06:05 pts/0    00:00:00 su - postgres

postgres  3320  3319  0 06:05 pts/0    00:00:00 -bash

postgres  3494  3320  0 06:22 pts/0    00:00:00 ps -ef

postgres  3495  3320  0 06:22 pts/0    00:00:00 grep --color=auto -i postgres

-bash-4.2$

-bash-4.2$

If postgreSQL cluster is not running then strat using below command 

-bash-4.2$

-bash-4.2$ pg_ctl -D /postgres/data/ start

waiting for server to start....2023-09-01 06:23:16.881 UTC [3508] LOG:  starting PostgreSQL 12.16 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit

2023-09-01 06:23:16.881 UTC [3508] LOG:  listening on IPv4 address "0.0.0.0", port 5432

2023-09-01 06:23:16.881 UTC [3508] LOG:  listening on IPv6 address "::", port 5432

2023-09-01 06:23:16.883 UTC [3508] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"

2023-09-01 06:23:16.887 UTC [3508] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"

2023-09-01 06:23:16.917 UTC [3508] LOG:  redirecting log output to logging collector process

2023-09-01 06:23:16.917 UTC [3508] HINT:  Future log output will appear in directory "log".

 done

server started

-bash-4.2$

-bash-4.2$

verify using below commnads 

-bash-4.2$

-bash-4.2$

-bash-4.2$ ps -ef | grep -i postgres

root      3318  3253  0 06:05 pts/0    00:00:00 sudo su - postgres

root      3319  3318  0 06:05 pts/0    00:00:00 su - postgres

postgres  3320  3319  0 06:05 pts/0    00:00:00 -bash

postgres  3508     1  0 06:23 ?        00:00:00 /usr/pgsql-12/bin/postgres -D /postgres/data

postgres  3509  3508  0 06:23 ?        00:00:00 postgres: logger

postgres  3511  3508  0 06:23 ?        00:00:00 postgres: checkpointer

postgres  3512  3508  0 06:23 ?        00:00:00 postgres: background writer

postgres  3513  3508  0 06:23 ?        00:00:00 postgres: walwriter

postgres  3514  3508  0 06:23 ?        00:00:00 postgres: autovacuum launcher

postgres  3516  3508  0 06:23 ?        00:00:00 postgres: stats collector

postgres  3517  3508  0 06:23 ?        00:00:00 postgres: logical replication launcher

postgres  3525  3320  0 06:23 pts/0    00:00:00 ps -ef

postgres  3526  3320  0 06:23 pts/0    00:00:00 grep --color=auto -i postgres

-bash-4.2$

-bash-4.2$

-bash-4.2$ psql

psql (12.16)

Type "help" for help.

postgres=# select version();

                                                 version

----------------------------------------------------------------------------------------------------------

 PostgreSQL 12.16 on x86_64-pc-linux-gnu, compiled by gcc (GCC) 4.8.5 20150623 (Red Hat 4.8.5-44), 64-bit

(1 row)

postgres=#

postgres=#

How to Lock the user account in Linux ?

 

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]# passwd -l postgres

Locking password for user postgres.

passwd: Success

Check the user account status :

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]# passwd -S postgres

postgres LK 2022-10-04 -1 -1 -1 -1 (Password locked.)

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]#

How to check the lock status of any Linux user Account ?

 

If user Locked 

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]# passwd -S postgres

postgres LK 2022-10-04 -1 -1 -1 -1 (Password locked.)

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]#

If user Unlocked

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]# passwd -S postgres

postgres PS 2022-10-04 -1 -1 -1 -1 (Password set, SHA512 crypt.)

[root@10.1.1.1 ~]#

[root@10.1.1.1 ~]#

========================

LK: Password locked

NP: No password

PS: Password set