How to stop a daemon from starting up on boot-up in Debian
update-rc.d was initially used by package upgrade scripts. remove is called on package uninstall and removes all links, defaults is called on package install, enable or disable might be used depending on debconf and are useful to sysadmins. The cleanups remove does are not in fact useful to disable a service. From the man page:
A common system administration error is to delete the links with the thought that this will "disable" the service, i.e., that this will prevent the service from being started. However, if all links have been deleted then the next time the package is upgraded, the package's postinst script will run update-rc.d again and this will reinstall links at their factory default locations. The correct way to disable services is to configure the service as stopped in all runlevels in which it is started by default. In the System V init system this means renaming the service's symbolic links from S to K.
sudo update-rc.d postgresql disable will do what you want, because it keeps the rc.d symlinks but with the K (killed, stopped) prefix. Revert it with an enable. Some services support being disabled from their /etc/defaults/$service file, but sadly there are exceptions. Other ways to disable a service are to chmod -x the /etc/init.d/$service file, or to insert an exit 0 at the top of it.
To clarify the best solution, similar to the answer Tobu gave:
- Do not use
update-rc.dwith theremoveoption. - Instead, use
update-rc.dwith thedisableoption.
Example: update-rc.d postgresql disable
PLUS, You can also find (and disable) other, more specific services with systemctl.
Example: systemctl disable pppd-dns.service
Tobu is absolutely right, but for completeness there is a tool to give you a smart overview: sysv-rc-conf. For copy&patse:
apt-get install sysv-rc-conf
Running sysv-rc-conf you'll see which script is executed in which runlevel. You can enable/disable services via space and quit with q.