Short answer: you can't. Ports below 1024 can be opened only by root. As per comment - well, you can, using CAP_NET_BIND_SERVICE, but that approach, applied to java bin will make any java program to be run with this setting, which is undesirable, if not a security risk.
The long answer: you can redirect connections on port 80 to some other port you can open as normal user.
Run as root:
# iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8080
As loopback devices (like localhost) do not use the prerouting rules, if you need to use localhost, etc., add this rule as well (thanks @Francesco):
# iptables -t nat -I OUTPUT -p tcp -d 127.0.0.1 --dport 80 -j REDIRECT --to-ports 8080
NOTE: The above solution is not well suited for multi-user systems, as any user can open port 8080 (or any other high port you decide to use), thus intercepting the traffic. (Credits to CesarB).
EDIT: as per comment question - to delete the above rule:
# iptables -t nat --line-numbers -n -L
This will output something like:
Chain PREROUTING (policy ACCEPT)
num target prot opt source destination
1 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:8080 redir ports 8088
2 REDIRECT tcp -- 0.0.0.0/0 0.0.0.0/0 tcp dpt:80 redir ports 8080
The rule you are interested in is nr. 2, so to delete it:
# iptables -t nat -D PREROUTING 2
You could manually symlink the /etc/init.d scripts from /etc/rc5.d/, to start when your GUI does. And you'd need another for shutdown.
But Debian has a more advanced (and better) method. This controls what gets linked from the individual runlevels init scripts. That's what the "BEGIN INIT INFO" is used for in the comments section at the top of those scripts.
If you're actually using Debian, instead of just using scripts from one of their resources, try using
update-rc.d celerybeat defaults
update-rc.d celeryd defaults
Best Answer
Use supervisord, it is superior to self-made sys-v-init scripts when it comes to manage several different processes. Celery ships with example configuration files that you can use to integrate it nicely into supervisord.
If you happen to use Debian as your choice of distribution you can even use the prepackaged supervisor:
For an example on how to use the "django-admin" command from the Debian python-django package with supervisor take a look at this blog post of mine.