Linux Init Systems Cheat Sheet
Easy way to tell which Init System you are using? And how to manipulate services in different Init System.
Tell the difference of Init Systems
systemd, SysVinit, Upstart, Supervisor
You must have heard these terms and known their job is “start other process”, but given a Linux system, can you tell which Init System it is using? And how to stop or disable service?
init is the first process run on Linux so it has pid=1. init keeps running as long as the system does. All other processes is started by init.
Earlier Linux distributions employed various Init System, but most latest distributions move to systemd.
| init | platfor | controller | directory | note |
|---|---|---|---|---|
| systemd | Red Hat family, Debian >= 8, Ubuntu >= 15.4 | systemctl | /etc/systemd/system/, /run/systemd/system/, /run/systemd/generator.late/, /usr/local/lib/systemd/system/, /usr/lib/systemd/system/ | compatible with SysVinit by systemd-sysv-generator, doesn’t honor priorities by /etc/rc?.d/ |
| SysVinit | earlier Linux | service | /etc/rc/, /etc/init.d/ | |
| Upstart | Ubuntu < 15.4 | start, stop, restart, status | /etc/init/ |
How to manipulate services?
| init | create | remove | start | stop | enable | disable |
|---|---|---|---|---|---|---|
| systemd | create unit_name.type_extension in /etc/systemd/system/ | rm /etc/systemd/system/unit_name.type_extension; systemctl daemon-reload; systemctl reset-failed | systemctl start foo | systemctl stop foo | systemctl enable foo | systemctl disable foo |
| SysVinit | create scripts in /etc/init.d, then run update-rc.d or chkconfig | mv /etc/init.d/foo.conf /etc/init/foo.conf.disabled | service foo start | service foo stop | update-rc.d foo enable | update-rc.d foo disable |
| Upstart | create /etc/init/foo.conf | mv /etc/init/foo.conf /etc/init/foo.conf.disabled | service foo start | service foo stop | rm /etc/init/foo.override | echo ‘manual’ | sudo tee /etc/init/foo.override |
systemctl daemon-reload; systemctl reset-failed
Supervisor looks simple, can it replace other Init System?
Brief answer: NO. Supervisor’s biggest advance is its convenience, but it just covers a subset features which can be done better by like systemd or SystemVinit.
Reference
https://unix.stackexchange.com/questions/233468/how-does-systemd-use-etc-init-d-scripts https://www.turnkeylinux.org/blog/debugging-systemd-sysv-init-compat http://linoxide.com/linux-command/systemd-vs-sysvinit-cheatsheet/ http://www.tecmint.com/systemd-replaces-init-in-linux/ http://www.pcworld.com/article/2841873/meet-systemd-the-controversial-project-taking-over-a-linux-distro-near-you.html http://www.tecmint.com/best-linux-init-systems/ https://askubuntu.com/questions/19320/how-to-enable-or-disable-services https://fedoraproject.org/wiki/SysVinit_to_Systemd_Cheatsheet