This is part of the Semicolon&Sons Code Diary - consisting of lessons learned on the job. You're in the unix category.
Last Updated: 2024-04-19
Systemctl is the interface to systemd.
Figure out how each of the myriad systems that boot with your machine has run (e.g. "successfully", "with errors", "timeouts", etc.)
systemctl
e.g. returns
UNIT LOAD ACTIVE SUB DESCRIPTION
snap-core-9804.mount loaded active mounted Mount unit for core, revision 9804
snap-core-9993.mount loaded active mounted Mount unit for core, revision 9993
var-lib-lxcfs.mount loaded active mounted /var/lib/lxcfs
acpid.path loaded active waiting ACPI Events Check
init.scope loaded active running System and Service Manager
lvm2-monitor.service loaded active exited Monitoring of LVM2 mirrors, snapshots etc. using dmeventd or progre
lxcfs.service loaded active running FUSE filesystem for LXC
lxd-containers.service loaded active exited LXD - container startup/shutdown
monit.service loaded active running LSB: service and resource monitoring daemon
nginx.service loaded active running A high performance web server and a reverse proxy server
This can be used in place of the old-fashioned way of checking boot messages. What's more, you can get even more info about a failed service (original PID, error code etc.) with the following:
# systemctl status UNIT
systemctl status lxd-containers.service
lxd-containers.service - LXD - container startup/shutdown
Loaded: loaded (/lib/systemd/system/lxd-containers.service; enabled; vendor preset: enabled)
Active: active (exited) since Wed 2019-06-26 09:10:07 UTC; 1 years 2 months ago
Docs: man:lxd(1)
Main PID: 635 (code=exited, status=0/SUCCESS)
Tasks: 0 (limit: 2319)
CGroup: /system.slice/lxd-containers.service
sudo systemctl enable monit
sudo systemctl restart monit
See document on systemd
sudo systemctl daemon-reload
This gets the system to pick up changes. Now you can restart an individual
service with systemctl restart SERVICE