Systemd Cheatsheet - Systemd Service Management Command Reference

Even if all you know is systemctl start or stop, it is worth walking through this set — it is the standard way to manage services on systemd distributions. Beyond start/stop and boot-enabling, it covers targeted journal log queries, timer scheduling, resource caps, and the control-group unit tree, answering three common questions: why a service fails to start, where to find its logs, and how to cap CPU or memory.

SysOps·47 commands·Last updated 2026-07-21

Service Management 8

systemctl start nginx

Start the service into the running state; does not add it to boot-enable, so it goes away on reboot

systemctl stop nginx

Stop the running service, running its ExecStop before exit; does not touch whether it is enabled at boot

systemctl restart nginx

Stop then start again; drops active connections, so prefer reload when the process holds persistent sessions

systemctl reload nginx

Gracefully reload config without dropping connections; not all services support reload

systemctl enable nginx

Enable the service to start at boot; add --now to also start it immediately

systemctl disable nginx

Disable the service from starting at boot

systemctl enable --now nginx

Enable at boot and start immediately

systemctl mask nginx

Fully disable a service so it cannot be started manually or pulled in by other units

Status 7

systemctl status nginx

Show service state and recent logs (most common)

systemctl is-enabled nginx

Show whether the service is enabled at boot

systemctl is-active nginx

Show whether the service is currently running

systemctl is-failed nginx

Check whether the service is in a failed state

systemctl list-units --type=service

List all loaded service units

systemctl list-unit-files --type=service

List all installed service files and their boot-enable state

systemctl list-units --failed

List failed services to troubleshoot startup errors

journalctl 8

journalctl -u nginx

Show logs for the specified service

journalctl -u nginx -f

Follow the service's logs in real time

journalctl --since "10 min ago" -u nginx

Show logs from the last 10 minutes

journalctl --since today --until "1 hour ago"

Filter logs by a time range

journalctl -p err -b

Show logs at error level and above since boot

journalctl -u nginx -n 100 --no-pager

Show the last 100 log lines without paging

journalctl --disk-usage

Show how much disk space journal logs use

journalctl --vacuum-size=100M

Vacuum logs, keeping only the most recent 100 MB

Targets & Runlevels 6

systemctl get-default

Show the default boot target (equivalent to the runlevel)

systemctl set-default multi-user.target

Set the default to multi-user (command-line) mode

systemctl set-default graphical.target

Set the default to graphical desktop mode

systemctl isolate multi-user.target

Switch to multi-user mode immediately (equivalent to init 3)

systemctl rescue

Enter rescue mode (requires root; stops non-essential services)

systemctl list-units --type=target

List all currently active targets

Timers 6

systemctl list-timers

List all scheduled timers (replaces crontab -l)

systemctl list-timers --all

List all timers, including inactive ones

systemctl status <timer>

Show a timer's state and next execution time

systemctl start <timer> && systemctl enable <timer>

Enable a timer and start it at boot

systemctl cat <timer>

Show the timer unit file contents

journalctl -u <timer>

Show logs of the service triggered by the timer

Service Config & Resource Control 6

systemctl cat nginx

Show the service's unit file contents

systemctl edit nginx

Edit a service override config, stored in override.conf

systemctl edit --full nginx

Edit the full unit file (not as an override)

systemctl daemon-reload

Reload systemd configuration after editing unit files

systemctl set-property nginx CPUQuota=50%

Limit the service to at most 50% CPU

systemctl set-property nginx MemoryMax=512M

Cap the service's memory at 512 MB

Troubleshooting & Analysis 6

systemctl --failed

Quickly show all failed services

systemctl reset-failed nginx

Clear the failed state of a service

systemd-analyze time

Show total boot time

systemd-analyze blame

List each service's startup time, sorted by duration

systemd-analyze critical-chain nginx

Show the startup dependency chain for a service

systemctl daemon-reload

Required after editing unit files, otherwise config won't take effect

Tips

reload gracefully reloads config without dropping connections, while restart recreates the process. Not all services support reload — nginx does.
journal logs rotate by default; if --disk-usage is too large, clean up with journalctl --vacuum-size=100M.
Timers are more controllable than crontab: you can see execution logs in journalctl and they support dependency relationships.
You must run systemctl daemon-reload after editing a unit file, otherwise systemd won't read the new config.
systemctl edit creates an override.conf snippet that doesn't modify the original unit file — safer.
mask is more thorough than disable: a masked service cannot be started manually or indirectly. Mask it before uninstalling a service.

Official References

Each command links to its official documentation below, so you can verify the latest usage and read deeper.

Linux man-pages

Maintained by LaoHand

Publicly updated on Jul 21, 2026, continuously proofread against official docs.

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