Postgresql-11 confusing situtation

Hi,

I’m using Postgresql 11.3 on Centos 7.6.18.10 server.

I have very unusual issue which I don’t know if it is OK:

I have running postgresql server with default instance:

[root@pgpmaster ~]# systemctl status postgresql-11

● postgresql-11.service - PostgreSQL 11 database server

   Loaded: loaded (/usr/lib/systemd/system/postgresql-11.service; enabled; vendor preset: disabled)

   Active: active (running) since Wed 2019-06-05 14:37:21 CEST; 49s ago

     Docs: https://www.postgresql.org/docs/11/static/

  Process: 3552 ExecStartPre=/usr/pgsql-11/bin/postgresql-11-check-db-dir ${PGDATA} (code=exited, status=0/SUCCESS)

Main PID: 3576 (postmaster)

    Tasks: 9

   CGroup: /system.slice/postgresql-11.service

           ├─3576 /usr/pgsql-11/bin/postmaster -D /var/lib/pgsql/11/data/

           ├─3609 postgres: logger

           ├─3621 postgres: checkpointer

           ├─3622 postgres: background writer

           ├─3623 postgres: walwriter

           ├─3624 postgres: autovacuum launcher

           ├─3625 postgres: archiver

           ├─3626 postgres: stats collector

           └─3627 postgres: logical replication launcher

Jun 05 14:37:20 pgpmaster.localhost systemd[1]: Starting PostgreSQL 11 database server...

Jun 05 14:37:20 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:20.923 CEST [3576] LOG:  listening on IPv4 address "0.0.0.0", port 5432

Jun 05 14:37:20 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:20.924 CEST [3576] LOG:  listening on IPv6 address "::", port 5432

Jun 05 14:37:20 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:20.928 CEST [3576] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"

Jun 05 14:37:21 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:21.026 CEST [3576] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"

Jun 05 14:37:21 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:21.123 CEST [3576] LOG:  redirecting log output to logging collector process

Jun 05 14:37:21 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:21.123 CEST [3576] HINT:  Future log output will appear in directory "log".

Jun 05 14:37:21 pgpmaster.localhost systemd[1]: Started PostgreSQL 11 database server.

If I restart it using systemctl restart postgresql-11 command, everything is OK, but if I use commands:

# pg_ctl -D /var/lib/pgsql/11/data/ -m immediate stop

# pg_ctl -D /var/lib/pgsql/11/data/ -m immediate start

Then I get following situtation:

# systemctl status postgresql-11

● postgresql-11.service - PostgreSQL 11 database server

   Loaded: loaded (/usr/lib/systemd/system/postgresql-11.service; enabled; vendor preset: disabled)

   Active: inactive (dead) since Wed 2019-06-05 14:41:32 CEST; 1min 40s ago

     Docs: https://www.postgresql.org/docs/11/static/

  Process: 3576 ExecStart=/usr/pgsql-11/bin/postmaster -D ${PGDATA} (code=exited, status=0/SUCCESS)

  Process: 3552 ExecStartPre=/usr/pgsql-11/bin/postgresql-11-check-db-dir ${PGDATA} (code=exited, status=0/SUCCESS)

Main PID: 3576 (code=exited, status=0/SUCCESS)

Jun 05 14:37:20 pgpmaster.localhost systemd[1]: Starting PostgreSQL 11 database server...

Jun 05 14:37:20 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:20.923 CEST [3576] LOG:  listening on IPv4 address "0.0.0.0", port 5432

Jun 05 14:37:20 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:20.924 CEST [3576] LOG:  listening on IPv6 address "::", port 5432

Jun 05 14:37:20 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:20.928 CEST [3576] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"

Jun 05 14:37:21 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:21.026 CEST [3576] LOG:  listening on Unix socket "/tmp/.s.PGSQL.5432"

Jun 05 14:37:21 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:21.123 CEST [3576] LOG:  redirecting log output to logging collector process

Jun 05 14:37:21 pgpmaster.localhost postmaster[3576]: 2019-06-05 14:37:21.123 CEST [3576] HINT:  Future log output will appear in directory "log".

Jun 05 14:37:21 pgpmaster.localhost systemd[1]: Started PostgreSQL 11 database server.

# ps agx | grep postgre

4592 pts/0    S      0:00 /usr/pgsql-11/bin/postgres -D /var/lib/pgsql/11/data

4593 ?        Ss     0:00 postgres: logger

4595 ?        Ss     0:00 postgres: checkpointer

4596 ?        Ss     0:00 postgres: background writer

4597 ?        Ss     0:00 postgres: walwriter

4598 ?        Ss     0:00 postgres: autovacuum launcher

4599 ?        Ss     0:00 postgres: archiver

4600 ?        Ss     0:00 postgres: stats collector

4601 ?        Ss     0:00 postgres: logical replication launcher

4630 pts/0    S+     0:00 grep --color=auto postgre

$ pg_ctl -D /var/lib/pgsql/11/data/ status

pg_ctl: server is running (PID: 4592)

/usr/pgsql-11/bin/postgres "-D" "/var/lib/pgsql/11/data"

Systemctl shows that database is dead, but it is actually running.

Can someone explain this behavioure?

Best regards!