Why I can't do anything with postgres? - postgresql

Question

I am using Linux Mint 17. I installed postgres with apt-get. I got postgres user account, I didn't have to create it. Then I login as postgres and followed these steps:
$ initdb -D /usr/local/pgsql/data
...
Success.
You can now start the database server of the Postgres-XC coordinator using:
postgres --coordinator -D /usr/local/pgsql/data
or
pg_ctl start -D /usr/local/pgsql/data -Z coordinator -l logfile
You can now start the database server of the Postgres-XC datanode using:
postgres --datanode -D /usr/local/pgsql/data
or
pg_ctl start -D /usr/local/pgsql/data -Z datanode -l logfile
Then I issued these 2 commands:
$ pg_ctl start -D /usr/local/pgsql/data -Z coordinator -l logfile
$ pg_ctl start -D /usr/local/pgsql/data -Z datanode -l logfile
I didn't get any response.
Then I tried createdb and createuser but I can't. Her you can see some informations, I hope it helps.
darko#darko-Lenovo-G570 ~ $ ps aux | grep postgres
postgre+ 1332 0.0 0.3 53304 6800 ? S 07:59 0:00 /usr/bin/postgres --datanode -D /var/lib/postgres-xc/DN1
postgre+ 1363 0.0 0.3 53304 6808 ? S 07:59 0:00 /usr/bin/postgres --datanode -D /var/lib/postgres-xc/DN2
postgre+ 1372 0.0 0.0 53304 1224 ? Ss 07:59 0:00 postgres: checkpointer process
postgre+ 1373 0.0 0.0 53304 1456 ? Ss 07:59 0:00 postgres: writer process
postgre+ 1374 0.0 0.0 53304 1224 ? Ss 07:59 0:00 postgres: wal writer process
postgre+ 1375 0.0 0.1 53724 2220 ? Ss 07:59 0:00 postgres: autovacuum launcher process
postgre+ 1376 0.0 0.0 23256 1256 ? Ss 07:59 0:00 postgres: stats collector process
postgre+ 1419 0.0 0.0 53304 1232 ? Ss 07:59 0:00 postgres: checkpointer process
postgre+ 1420 0.0 0.0 53304 1464 ? Ss 07:59 0:00 postgres: writer process
postgre+ 1421 0.0 0.0 53304 1232 ? Ss 07:59 0:00 postgres: wal writer process
postgre+ 1423 0.0 0.1 53724 2228 ? Ss 07:59 0:00 postgres: autovacuum launcher process
postgre+ 1424 0.0 0.0 23256 1264 ? Ss 07:59 0:00 postgres: stats collector process
postgre+ 1440 0.0 0.3 53304 6856 ? S 07:59 0:00 /usr/bin/postgres --coordinator -D /var/lib/postgres-xc/CN
postgre+ 1451 0.0 0.0 53304 1224 ? Ss 07:59 0:00 postgres: pooler process
postgre+ 1453 0.0 0.0 53304 1712 ? Ss 07:59 0:00 postgres: checkpointer process
postgre+ 1454 0.0 0.0 53304 1464 ? Ss 07:59 0:00 postgres: writer process
postgre+ 1455 0.0 0.0 53304 1456 ? Ss 07:59 0:00 postgres: wal writer process
postgre+ 1456 0.0 0.5 63548 11736 ? Ss 07:59 0:00 postgres: autovacuum launcher process
postgre+ 1457 0.0 0.0 23256 1264 ? Ss 07:59 0:00 postgres: stats collector process
postgre+ 1481 0.0 0.1 16412 2716 ? S 07:59 0:00 /usr/bin/gtm -D /var/lib/postgres-xc/GTM -l /var/log/postgres-xc/datanode.log
darko 8426 0.0 0.0 5908 856 pts/0 S+ 18:34 0:00 grep --colour=auto postgres
darko#darko-Lenovo-G570 ~ $ sudo -u postgres -i
[sudo] password for darko:
postgres#darko-Lenovo-G570 ~ $ createuser darko
createuser: could not connect to database postgres: FATAL: role "postgres" does not exist

Answer 1

I was confused with roles, databases and privilegies so I decided to remove postgresql and install it again. Actually I think that I didn't install it correctly at first because first installation was
$ sudo apt-get install postgresql
and nothing worked for me, as I described in question. So I decided to kill all postgres processes:
$ sudo pkill postgres
remove postgresql
$ sudo apt-get remove postgresql
and build postgresql form source as described in manual postgresql-9.6-A4.pdf (you can download it from internet). This manual is great, you can find everything there.
MAYBE SOME OF MY COMMANDS ARE NOT 100% CORRECT BECAUSE IT HAS PASSED FEW DAYS SINCE I SOLVED MY PROBLEM.