Day: 30 March, 2015

As systemd becomes the default method of handling services in all major Linux distributions, below are some quick and easy-to-remember commands that will make you look like a pro.

systemctl

• check for all running units
  systemctl
  TIP: To show all units, including in-active ones:
  systemctl list-unit-files

• Check for failed units
  systemctl --failed

• Start, stop, restart units
  systemctl start postfix.service
systemctl restart postfix.service
systemctl stop postfix.service

• Check status of a specific unit
  systemctl status mysqld.service
  TIP: Use -l for detailed status

• Enable or disable services
  systemctl enable firewalld.service
systemctl disable NetworkManager.service
TIP: If you disable a service, and it still runs,
  systemctl mask NetworkManager.service
  Use ‘unmask’ to restore it

• See if a specific unit is enabled
  systemctl is-enabled iptables.service

• Create a snapshot – useful for testing various targets
  systemctl snapshot example.snapshot
  TIP: To activate it:
  systemctl isolate example.snapshot


• Reboot/poweroff/suspend your machine
  systemctl reboot
systemctl poweroff
systemctl suspend

• Change current target – i.e. runlevel
  systemctl isolate graphical.target

• To list current target
  systemctl list-units --type=target

systemd

• See which units take a long time to start during boot up
  systemd-analyze blame
  TIP: You can plot the boot up using:
  systemd-analyze plot

• See when a unit started and how long it took
  systemd-analyze critical-chain

journalctl

• Create a running log like ‘tail -f /var/log/messages’
  journalctl -f -o cat --no-pager

• Running log for a specific unit
  journalctl -f -o cat --no-pager -u httpd.service

• See boot messages – like ‘dmesg’
  journalctl -b

Manage remote systems:
systemctl status sshd -H root@1.2.3.4

For detailed instructions on these and more commands, man as always is your best friend.