• it is a convention for daemon progams to end in the letter d
  • systemctl command is used to manage units e.g. display available units systemctl -t help

Listing service units

systemctl list-units --type=service [--all]
systemctl list-unit-files --type=service # + installed but not enabled

Viewing service states

systemctl status <name.type>
systemctl status sshd.service

Verifying the status of a service

systemctl is-active sshd.service
... is-enabled ...
... is-failed ...

Service controls

systemctl start ...
systemctl stop ...
systemctl restart ...
systemctl reload ... # just reloads config files without restart. This does not change pid
systemctl reload-or-restart ... # reloads if possible, otherwise restarts
systemctl list-dependencies ... # displays hierarchy mapping

Masking and Unmasking

  • This prevents a service from starting by crating a symlink to /dev/null.
systemctl mask ...
systemctl unmask ...

Enabling services to start / stop at boot

  • starting / stopping on a running system does not guarantee that the service auto starts/stops when the system reboots.

  • GRUB2 - GRand Unified Bootloader v2

selecting a target to boot at runtime

# systemctl isolate <target>
# e.g.
systemctl isolate multi-user.target

get and set the default target (persistent)

systemctl get-default
# systemctl set-default <target> e.g.
systemctl set-default multi-user.target # graphical.target
systemctl reboot # reboots to cli interface instead of gui