Utility update-rc.d is part of sysv init (package sysv-rc) on Ubuntu Linux. It can be used to manage services at boot time. It can be used to add or remove a service from auto start list. Note that this is only relevant for non upstart based services. Some upstart and sysv init based services at the time of writing this tutorial are:
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sysv init based: apache2, memcached, jenkin, etc. This tutorial is only relevant for sysv init based services. -
upstart based: mysql, docker, etc.
What does update-rc.d do?
update-rc.d creates symlinks in /etc/rc*.d/ for various run levels pointing to /etc/init.d/service_script (e.g. /etc/init.d/apache2) when a service is enabled to auto start on boot.
Add a service to auto start at boot time in dry-run mode
We’ll use nginx for this example. Also note that -n is for dryrun.
## dry-run $ sudo update-rc.d -n nginx defaults Adding system startup for /etc/init.d/nginx ... /etc/rc0.d/K20nginx -> ../init.d/nginx /etc/rc1.d/K20nginx -> ../init.d/nginx /etc/rc6.d/K20nginx -> ../init.d/nginx /etc/rc2.d/S20nginx -> ../init.d/nginx /etc/rc3.d/S20nginx -> ../init.d/nginx /etc/rc4.d/S20nginx -> ../init.d/nginx /etc/rc5.d/S20nginx -> ../init.d/nginx
Add a service to auto start at boot time in real-run mode
We’ll use nginx for this example. Also note that we are not using -n here.
## real-run $ sudo update-rc.d nginx defaults Adding system startup for /etc/init.d/nginx ... /etc/rc0.d/K20nginx -> ../init.d/nginx /etc/rc1.d/K20nginx -> ../init.d/nginx /etc/rc6.d/K20nginx -> ../init.d/nginx /etc/rc2.d/S20nginx -> ../init.d/nginx /etc/rc3.d/S20nginx -> ../init.d/nginx /etc/rc4.d/S20nginx -> ../init.d/nginx /etc/rc5.d/S20nginx -> ../init.d/nginx
See if a service will start at boot time
To so if service nginx will start at boot time we can use two approaches.
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By adding service to auto start in dry-run mode (-n). This will work if service has been added by update-rc.d.
## dry-run $ sudo update-rc.d -n nginx defaults System start/stop links for /etc/init.d/nginx already exist.
If we get “already exist” message, that means service will autostart at boot time.
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By viewing files in
/etc/rc*.d/$ ls /etc/rc*.d/*nginx* /etc/rc0.d/K20nginx /etc/rc1.d/K20nginx /etc/rc2.d/S20nginx /etc/rc3.d/S20nginx /etc/rc4.d/S20nginx /etc/rc5.d/S20nginx /etc/rc6.d/K20nginx
Presence of these script in /etc/rc*.d/* implies that nginx will autostart at reboot.
Remove a service from auto start at boot time in dry-run mode
We’ll use nginx for this example. Also note that -n is for dryrun. When service auto start is in enabled state, you will get the following outcome.
## dry-run $ sudo update-rc.d -n -f nginx remove Removing any system startup links for /etc/init.d/nginx ... /etc/rc0.d/K20nginx /etc/rc1.d/K20nginx /etc/rc2.d/S20nginx /etc/rc3.d/S20nginx /etc/rc4.d/S20nginx /etc/rc5.d/S20nginx /etc/rc6.d/K20nginx
Remove a service from auto start at boot time in real-run mode
We’ll use nginx for this example. Also note that -n is not present here. When service auto start is setup, you will get the following outcome.
## real-run $ sudo update-rc.d -f nginx remove Removing any system startup links for /etc/init.d/nginx ... /etc/rc0.d/K20nginx /etc/rc1.d/K20nginx /etc/rc2.d/S20nginx /etc/rc3.d/S20nginx /etc/rc4.d/S20nginx /etc/rc5.d/S20nginx /etc/rc6.d/K20nginx
