Which command to use to restart postgresql 12 service

Question

I am about to restart postgresql 12 service running on Ubuntu 18. First, I check it's status : sudo service postgresql status. Its says :

postgresql.service - PostgreSQL RDBMS
 Loaded: loaded (/lib/systemd/system/postgresql.service; disabled; vendor pres
 Active: inactive (dead)
lines 1-3/3 (END)...skipping...
postgresql.service - PostgreSQL RDBMS
 Loaded: loaded (/lib/systemd/system/postgresql.service; disabled; vendor preset: enabled)
 Active: inactive (dead)

Although it appears to be inactive, but I still can connect.

Then I run another checking : systemctl status postgresql@12-main. it says :

root@db-services:/# systemctl status postgresql@12-main
●くろまる [email protected] - PostgreSQL Cluster 12-main
 Loaded: loaded (/etc/systemd/system/[email protected]; enabled; vendor preset: enabled)
 Drop-In: /etc/systemd/system/[email protected]
 └─override.conf
 Active: active (running) since Mon 2022年06月13日 09:02:25 WIB; 5 months 27 days ago
 Main PID: 5807 (postgres)
 Tasks: 86 (limit: 4915)
 CGroup: /system.slice/system-postgresql.slice/[email protected]
 ├─ 1586 postgres: 12/main: postgres db_sync 10.100.3.248(61414) idle
 ├─ 1588 postgres: 12/main: postgres db_sync 10.100.3.248(61415) idle
 ├─ 1606 postgres: 12/main: docreg db_docreg 10.100.8.150(18385) idle
 ├─ 1607 postgres: 12/main: docreg db_docreg 10.100.8.150(18399) idle
 ├─ 1608 postgres: 12/main: docreg db_docreg 10.100.8.150(18401) idle
 ├─ 1609 postgres: 12/main: docreg db_docreg 10.100.8.150(18421) idle
 ├─ 2592 postgres: 12/main: docudigtl db_docudigtl 10.100.8.112(34956) idle
 ├─ 3518 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(48290) idle
 ├─ 5150 postgres: 12/main: docudigtl db_docudigtl 10.100.7.114(61504) idle
 ├─ 5807 /usr/lib/postgresql/12/bin/postgres -D /data/postgresql/12/main -c config_file=/etc/postgresql/12/main/postgresql.co
 ├─ 5883 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(48626) idle
 ├─ 6316 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(48704) idle
 ├─ 7049 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(48870) idle
 ├─ 7986 postgres: 12/main: docudigtl db_docudigtl 10.100.7.114(56240) idle
 ├─ 8146 postgres: 12/main: docudigtl db_docudigtl 10.100.8.114(47432) idle
 ├─ 8183 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(49022) idle
 ├─ 8360 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(49036) idle
 ├─ 8445 postgres: 12/main: docudigtl db_docudigtl 10.100.8.114(47478) idle
 ├─ 9590 postgres: 12/main: docudigtl db_docudigtl 10.100.8.106(56094) idle
 ├─ 9687 postgres: 12/main: docudigtl db_docudigtl 10.100.8.112(50980) idle
 ├─10148 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(40646) idle
 ├─10324 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(40680) idle
 ├─11079 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(49496) idle
 ├─11602 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(58152) idle
 ├─11886 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(44674) idle
 ├─12106 postgres: 12/main: docudigtl db_docudigtl 127.0.0.1(49618) idle
 ├─13112 postgres: 12/main: docudigtl db_docudigtl 10.100.6.145(55014) idle
 ├─13122 postgres: 12/main: docudigtl db_docudigtl 10.100.6.145(55015) idle
 ├─13145 postgres: 12/main: docudigtl db_mysapk 10.100.6.145(55016) idle
 ├─13202 postgres: 12/main: docudigtl db_docudigtl 10.100.7.114(62073) idle
 ├─13945 postgres: 12/main: checkpointer
 ├─13946 postgres: 12/main: background writer
 ├─13947 postgres: 12/main: walwriter
 ├─13948 postgres: 12/main: autovacuum launcher
 ├─13949 postgres: 12/main: stats collector
 ├─13950 postgres: 12/main: logical replication launcher

So it is actually active !

Then I do sudo service --status-all | grep postgresql. It says :

[ - ] postgresql

1. Whats the difference between systemctl restart postgresql@12-main VS sudo service postgresql restart?
2. Which one should I use for restart : systemctl restart postgresql@12-main OR sudo service postgresql restart ?

For comparison, on another server, if I do sudo service postgresql status. It says :

postgresql.service - PostgreSQL RDBMS
 Loaded: loaded (/lib/systemd/system/postgresql.service; enabled; vendor preset: enabled)
 Active: active (exited) since Mon 2022年12月05日 18:37:03 WIT; 4 days ago
 Process: 22666 ExecStart=/bin/true (code=exited, status=0/SUCCESS)
 Main PID: 22666 (code=exited, status=0/SUCCESS)
Dec 05 18:37:03 db-profile-mtr systemd[1]: Starting PostgreSQL RDBMS...
Dec 05 18:37:03 db-profile-mtr systemd[1]: Started PostgreSQL RDBMS.

And when I do systemctl status postgresql@12-main, it says :

[email protected] - PostgreSQL Cluster 12-main
 Loaded: loaded (/etc/systemd/system/[email protected]; enabled-runtime; vendor preset: enabled)
 Active: active (running) since Mon 2022年12月05日 18:37:03 WIT; 4 days ago
 Process: 22609 ExecStop=/usr/bin/pg_ctlcluster --skip-systemctl-redirect -m fast 12-main stop (code=exited, status=0/SUCCESS)
 Process: 22631 ExecStart=/usr/bin/pg_ctlcluster --skip-systemctl-redirect 12-main start (code=exited, status=0/SUCCESS)
 Main PID: 22637 (postgres)
 Tasks: 119 (limit: 4915)
 CGroup: /system.slice/system-postgresql.slice/[email protected]
 ├─ 417 postgres: 12/main: refer db_ref 10.100.9.50(53216) idle
 ├─ 965 postgres: 12/main: refer db_ref 10.100.9.50(53514) idle
 ├─ 1709 postgres: 12/main: profiling db_profile 127.0.0.1(34158) idle
 ...many proceses all the way down

Then I do sudo service --status-all | grep postgresql. And it says :

 [ + ] postgresql

Need advice / help. Thanks

Answer 1

Probably neither, as there are actually two variables:

1. Command.
   • The service command is legacy from SysVInit.
   • The systemctl comes with SystemD and replaces SysVInit; use it.
2. Postgresql services on Ubuntu.
   • postgresql.service controls all Postgresql instances.
   • [email protected] is a single instance; there could be multiple.

To restart all instances: sudo systemctl restart postgresql.

There's a longer explanation on AskUbuntu.

• padjee: Finally I did it using sudo service postgresql restart. Now when I do sudo service postgresql status it shows : postgresql.service - PostgreSQL RDBMS Loaded: loaded (/lib/systemd/system/postgresql.service; disabled; vendor preset: enabled) Active: active (exited) since Sun 2022年12月11日 00:38:06 WIB; 11s ago Process: 3095 ExecStart=/bin/true (code=exited, status=0/SUCCESS) Main PID: 3095 (code=exited, status=0/SUCCESS) . All is well. Thanks @EsaJokinen.