systemd cheat sheet

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CHANGING SYSTEM STATES
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systemctl reboot                    # Reboot the system (reboot.target)
systemctl poweroff                  # Power off the system (poweroff.target)
systemctl emergency                 # Put in emergency mode (emergency.target)
systemctl default                   # Back to default target (multi-user.target


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WORKING WITH <service>
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systemctl stop <service>            # Stop a running <service>
systemctl start <service>           # Start a <service>
systemctl restart <service>         # Restart a running <service>
systemctl reload <service>          # Reload all config files in <service>
systemctl status <service>          # See if <service> is running/enabled
systemctl enable <service>          # Enable a <service> to start on boot
systemctl is-enabled <service>      # Check whether a service is enabled
systemctl disable <service>         # Disable <service> -- won’t start at boot
systemctl enable --now <service>    # Enable and start in one go
systemctl disable --now <service>   # Disable and stop in one go
systemctl show <service>            # Show properties of a <service> (or other unit)
systemctl daemon-reload             # After directly modifying/adding config files
systemctl reset-failed <service>    # Remove unit from failed list (allow auto restart again)



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VIEW systemd INFORMATION
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systemctl list-dependencies         # Show a unit’s dependencies
systemctl list-sockets              # List sockets and what activates
systemctl list-jobs                 # View active systemd jobs
systemctl list-unit-files           # See unit files and their states
systemctl list-units                # Show if units are loaded/active
systemctl get-default               # List default target (like run level


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VIEWING LOG MESSAGES
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journalctl                          # Show all collected log messages
journalctl -b                       # Print everything since boot
journalctl -e                       # Print last page of the journal 
journalctl -u <service>.            # See message of the specified unit
journalctl -f                       # Follow messages as they appear
journalctl -k                       # Show only kernel messages
journalctl --no-pager               # Non-interactive mode
journalctl --disk-usage             # Show space used by logs
journalctl --rotate                 # Force log rotation
journalctl --vacuum-size=100M       # Remove logs until <100MB is used
journalctl --vacuum-time=2weeks     # Remove logs older 2 weeks

### Need to add unit file options frome following

## Ref 1 : https://www.freedesktop.org/software/systemd/man/systemd.service.html
## Ref 2 : https://www.freedesktop.org/software/systemd/man/systemd.unit.html#
## Ref 3 : https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/System_Administrators_Guide/sect-Managing_Services_with_systemd-Unit_Files.html

### Reference

## Ref 1 : https://access.redhat.com/sites/default/files/attachments/rh_systemd_reference_card_0914_jcs_print_2.pdf