Answer by Alaa Ali for How to install an init.d script?

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/celerydsudo 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.