Listing Linux services with systemctl

Services on Linux are background programs — your web server, SSH daemon, cron, etc. They can be started at boot or on demand. Knowing how to list and inspect them quickly is core to debugging anything systems-related. Most modern distros use systemd as the init system and service manager, and systemctl is the CLI you talk to it with.

Listing services

Show all loaded services (running or not):

bash

1sudo systemctl list-units --type service

Sample output:

bash

1  UNIT                                           LOAD   ACTIVE SUB     DESCRIPTION2  accounts-daemon.service                        loaded active running Accounts Service3  apparmor.service                               loaded active exited  Load AppArmor profiles4  apport.service                                 loaded active exited  LSB: automatic crash report generation5  atd.service                                    loaded active running Deferred execution scheduler6  blk-availability.service                       loaded active exited  Availability of block devices7  cloud-config.service                           loaded active exited  Apply the settings specified in cloud-config8  ...

Each row shows:

UNIT — service name
LOAD — whether the unit file is loaded into memory
ACTIVE — high-level state: active, reloading, inactive, failed, activating, deactivating
SUB — fine-grained state: running, dead, exited, failed, etc.
DESCRIPTION — short description from the unit file

To include services that aren't loaded into memory:

bash

1sudo systemctl list-units --type service --all

Checking a service's status

bash

1sudo systemctl status <service-name>

For example, Nginx:

bash

1sudo systemctl status nginx.service

bash

1● nginx.service - A high performance web server and a reverse proxy server2     Loaded: loaded (/lib/systemd/system/nginx.service; enabled; vendor preset: enabled)3    Drop-In: /etc/systemd/system/nginx.service.d4             └─limits.conf5     Active: active (running) since Tue 2022-02-08 00:41:13 +03; 2 days ago6   Main PID: 21684 (nginx)7      Tasks: 68 (limit: 2367)8     Memory: 72.6M9     CGroup: /system.slice/nginx.service10             ├─21684 nginx: master process /usr/sbin/nginx11             ├─21685 nginx: worker process12             ├─21686 nginx: worker process13             └─21687 nginx: cache manager process1415Feb 08 00:41:13 linuxpedi systemd[1]: Starting A high performance web server and a reverse proxy server...16Feb 08 00:41:13 linuxpedi nginx[21682]: nginx: the configuration file /etc/nginx/nginx.conf syntax is ok17Feb 08 00:41:13 linuxpedi nginx[21682]: nginx: configuration file /etc/nginx/nginx.conf test is successful18Feb 08 00:41:13 linuxpedi systemd[1]: Started A high performance web server and a reverse proxy server.

Useful fields:

Loaded — whether the unit is loaded, the path to the unit file, and whether it's enabled at boot
Active — running state (the green ● in colour-aware terminals) and how long it's been up
Main PID — the process's PID
Memory — current RAM usage
CGroup — the cgroup tree of PIDs the service owns

Quick checks

Just want a yes/no on whether a service is running?

bash

1systemctl is-active nginx.service

Other handy variants:

bash

1systemctl is-enabled nginx.service     # will it start at boot?2systemctl is-failed nginx.service      # did it crash?

For a one-line per-service summary across the whole box, I usually pair these with journalctl -u <service> -n 50 to follow the recent logs.