How to install an init.d script?

When you copy the script into place, don't forget to make it executable and owned by root:

sudo chmod +x /etc/init.d/celeryd
sudo chown root:root /etc/init.d/celeryd

Once you have installed that, you can set it to start automatically on boot with:

sudo update-rc.d celeryd defaults
sudo update-rc.d celeryd enable

Your celeryd script is probably not executable, that's why sudo /etc/init.d/celeryd is returning command not found. So, you need to first make it executable.

To do so, run the following commands:

sudo chmod 755 /etc/init.d/celeryd
sudo chown root:root /etc/init.d/celeryd

The first line changes the permissions to -rwxr-xr-x, and the second line ensures that the owner and group owner of the file is root.

Once this is done, I assume you will need to use sudo /etc/init.d/celeryd start to start the daemon.

If you get the command not found error when you run insserv, you may fix it by running the following command:

sudo ln -s /usr/lib/insserv/insserv /sbin/insserv

Then see insserv -h or man insserv for help.

Also you can try with:

sudo update-rc.d celeryd defaults

Source: https://askubuntu.com/a/334043/147044