Unable to start postgresql service on CentOS 7 - linux

Question

Unable to start postgresql-9.5 on CentOS 7.
I followed this page - https://wiki.postgresql.org/wiki/YUM_Installation - for installing the database server on CentOS.
I tried the same after setting setenforce 0, and that did not help either.
I am doing all operations as root.
systemctl start postgresql-9.5.service
Job for postgresql-9.5.service failed because the control process exited with error
code. See "systemctl status postgresql-9.5.service" and "journalctl -xe" for details.
And here is what I get for status -
Redirecting to /bin/systemctl status postgresql-9.5.service
● postgresql-9.5.service - PostgreSQL 9.5 database server
Loaded: loaded (/usr/lib/systemd/system/postgresql-9.5.service; enabled; vendor preset: disabled)
Active: failed (Result: exit-code) since Thu 2016-02-18 15:20:30 EST; 2min 28s ago
Process: 15041 ExecStartPre=/usr/pgsql-9.5/bin/postgresql95-check-db-dir ${PGDATA} (code=exited, status=1/FAILURE)
Feb 18 15:20:30 myserver systemd[1]: Starting PostgreSQL 9.5 database server...
Feb 18 15:20:30 myserver systemd[1]: postgresql-9.5.service: control process exited, code=exited status=1
Feb 18 15:20:30 myserver systemd[1]: Failed to start PostgreSQL 9.5 database server.
Feb 18 15:20:30 myserver systemd[1]: Unit postgresql-9.5.service entered failed state.
Feb 18 15:20:30 myserver systemd[1]: postgresql-9.5.service failed.
And the contents of the different conf files are as follows -
[root#myserver /]# cat /etc/ld.so.conf.d/postgresql-pgdg-libs.conf
/usr/pgsql-9.5/lib/
[root#myserver /]# cat /usr/lib/tmpfiles.d/postgresql-9.5.conf
d /var/run/postgresql 0755 postgres postgres -
[root#myserver /]# cat /usr/pgsql-9.5/share/postgresql-9.5-libs.conf
/usr/pgsql-9.5/lib/
[root#myserver /]# cat /etc/alternatives/pgsql-ld-conf
/usr/pgsql-9.5/lib/
[root#myserver /]# cat /var/lib/alternatives/pgsql-ld-conf
auto
/etc/ld.so.conf.d/postgresql-pgdg-libs.conf
/usr/pgsql-9.5/share/postgresql-9.5-libs.conf
950
Googled for the error that I am seeing.
A number of folks have seen the same error, and the underlying cause is different in each case. Reading through those posts, it is not clear that I am seeing any of the already reported causes.

Answer 1

Make sure you have installed all packages correctly and updated yum repository sections [base] and [updates] before installation as it mentioned in the guide . We have CentOS 7 with PostgreSQL 9.5 and it works perfectly fine with following steps:
vi /etc/yum.repos.d/CentOS-Base.repo
yum localinstall http://yum.postgresql.org/9.5/redhat/rhel-7-x86_64/pgdg-centos95-9.5-2.noarch.rpm
yum list postgres*
yum install -y postgresql95-server.x86_64 postgresql95-contrib.x86_64 postgresql95-libs.x86_64
/usr/pgsql-9.5/bin/postgresql95-setup initdb
systemctl enable postgresql-9.5.service
systemctl start postgresql-9.5.service
and finally, systemctl status postgresql-9.5.service should show you something like this:
postgresql-9.5.service - PostgreSQL 9.5 database server
Loaded: loaded (/usr/lib/systemd/system/postgresql-9.5.service; enabled)
Active: active (running) since Fri 2016-02-19 00:01:13 UTC; 6min ago
Process: 10809 ExecStart=/usr/pgsql-9.5/bin/pg_ctl start -D ${PGDATA} -s -w -t 300 (code=exited, status=0/SUCCESS)
Process: 10802 ExecStartPre=/usr/pgsql-9.5/bin/postgresql95-check-db-dir ${PGDATA} (code=exited, status=0/SUCCESS)
Main PID: 10811 (postgres)
CGroup: /system.slice/postgresql-9.5.service
├─10811 /usr/pgsql-9.5/bin/postgres -D /var/lib/pgsql/9.5/data
├─10812 postgres: logger process
├─10814 postgres: checkpointer process
├─10815 postgres: writer process
├─10816 postgres: wal writer process
├─10817 postgres: autovacuum launcher process
└─10818 postgres: stats collector process

Answer 2

The most common issue is that the database cluster was not initialized. You can initialize it easily by running the postgresql-XX-setup script with the initdb command, e.g.
sudo /usr/pgsql-11/bin/postgresql-11-setup initdb
Then start the Postgres service, e.g.
sudo systemctl start postgresql-11

Answer 3

These steps helped me on our test server.
Connect your server via SSH.
Then switch user:
sudo su - postgres
Check Postgres status:
pg_ctl status
Stop DB:
pg_ctl stop
Check if no server processes exist:
ps axf | grep postg
Start Postgres service:
sudo systemctl start postgresql.service
OR
sudo systemctl start postgresql
Then check status:
systemctl status postgresql.service ИЛИ systemctl status postgresql