Unable to start postgresql.service?

For PostGres 9.4.12, I tried the following and it worked:

./pg_ctl start

You can check the status of it:

./pg_ctl status

Finally, I figured this one out. There was already a file present

/usr/lib/systemd/system/postgresql-9.6.service

So, may be due to the presence of this file, I was not able to start postgresql.service. Then I tried to start postgresql-9.6.service as follows:

[code_master5@BitBox ~]$ sudo systemctl start postgresql-9.6.service
Failed to start postgresql-9.6.service: Unit postgresql-9.6.service not found.

And, as you can see the output, again it failed.

I simply deleted the file using sudo as I thought may be postgresql.service file is not being created by relevant program due to the presence of this file. Then I restarted the system. It's working fine since then, as you can see the output below:

[code_master5@BitBox ~]$ sudo systemctl status postgresql.service
[sudo] password for code_master5: 
● postgresql.service - PostgreSQL database server
Loaded: loaded (/usr/lib/systemd/system/postgresql.service; enabled; vendor p
Active: active (running) since Sat 2017-01-28 09:31:30 IST; 7h ago
Main PID: 342 (postgres)
Tasks: 6 (limit: 4915)
CGroup: /system.slice/postgresql.service
       ├─342 /usr/bin/postgres -D /var/lib/postgres/data
       ├─358 postgres: checkpointer process   
       ├─359 postgres: writer process   
       ├─360 postgres: wal writer process   
       ├─361 postgres: autovacuum launcher process   
       └─362 postgres: stats collector process   

Jan 28 09:31:26 BitBox systemd[1]: Starting PostgreSQL database server...
Jan 28 09:31:28 BitBox postgres[340]: FATAL:  the database system is starting up
Jan 28 09:31:28 BitBox postgres[340]: LOG:  database system was shut down at 201
Jan 28 09:31:29 BitBox postgres[340]: FATAL:  the database system is starting up
Jan 28 09:31:29 BitBox postgres[340]: LOG:  MultiXact member wraparound protecti
Jan 28 09:31:29 BitBox postgres[340]: LOG:  database system is ready to accept c
Jan 28 09:31:29 BitBox postgres[340]: LOG:  autovacuum launcher started
Jan 28 09:31:30 BitBox systemd[1]: Started PostgreSQL database server.

I would surely like to warn all those having same problem. Please do whatever I did at your own risk. Since these are system files. Messing with these can spoil your weekend!

I am still a bit confused on this though. Explanations are welcome!

I found these two commands very handy. Although this post is old, maybe others will be benefited from this in the future.

systemctl list-units|grep postgresql
service postgresql-12.service restart

Try this:

service postgresql-10.service restart
service postgresql-XX.service restart