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README

Demonstrates some examples with systemd

Creating a systemd service example 22_systemd_service.
Some journalctl examples here.

REF: github.com/chrisguest75/shell_examples/27_journalctl/README.md

Centents

TODO:

  • Add a timer and a socket example.

Examples

Help

# show unit types
systemctl list-units -t help  

# show help for different units
man systemd.unit
man systemd.service 
man systemd.timer

Targets

A unit configuration file whose name ends in ".target" encodes information about a target unit of systemd, which is used for grouping units and as well-known synchronization points during start-up.

# list targets
systemctl list-units --type target
# show unit file for timers.target 
systemctl cat timers.target

Services

A unit configuration file whose name ends in ".service" encodes information about a process controlled and supervised by systemd.

# Show properties of one or more units/jobs or the manager
systemctl show --no-pager   
# list services
systemctl list-units -t service --no-pager 
systemctl list-units -t service --state running

# status of service
systemctl status zfs-zed.service  

# list the unit files
systemctl cat zfs-import-cache.service

Sockets

A unit configuration file whose name ends in ".socket" encodes information about an IPC or network socket or a file system FIFO controlled and supervised by systemd, for socket-based activation.

systemctl list-units --type socket 
systemctl cat uuidd.socket

Timers

A unit configuration file whose name ends in ".timer" encodes information about a timer controlled and supervised by systemd, for timer-based activation.

systemctl list-timers --no-pager --all   
systemctl cat fstrim.timer

Run

systemd-run
systemd-run --user --on-calendar '*:0/1' ./script.sh --arg1

Troubleshooting

# if a timer is failing to be removed "not-found"
systemctl reset-failed      

# what has failed?
systemctl --failed

# look at logs for a service
journalctl -b -u docker.service 

# top for systemd services
systemd-cgtop  


systemd-analyze blame 

# 
systemd-analyze plot --help    
systemd-analyze plot > ./graph1.svg  
xdg-open ./graph1.svg 

# reload systemd
systemctl daemon-reload

Controlling Server

systemctl reboot -i  

loginctl

Resources

  • cheatsheet systemd
  • cheatsheet systemctl
  • Systemd Units Explained with Types and States here
  • How To Use Systemctl to Manage Systemd Services and Units here
  • Understanding and administering systemd here
  • More Systemd Fun: The Blame Game And Stopping Services With Prejudice help
  • Use systemd timers instead of cronjobs here