Run a service after networking is ready on Ubuntu?

Question

I'm trying to start a service that depends on networking being started, whenever the computer is rebooted. I have a few questions:

1. Is this easily possible from an /etc/init.d script? I have tried creating a script here (conforming to the standards), but I'm really doubtful that it's even running on boot, let alone working. When I test it manually, it works.

2. I've seen the new Upstart service, but as far as how that actually works, I'm completely in the dark.

How can I make a script that runs on boot which runs after networking has been started? If I could run it after connected to wireless network, even better :)

Answer 1

You can use files in /etc/init as models. For example, this is /etc/init/mountall-net.conf:

# mountall-net - Mount network filesystems
#
# Send mountall the USR1 signal to inform it to try network filesystems
# again.

description     "Mount network filesystems"

start on net-device-up

task

script
    PID=$(status mountall 2>/dev/null | sed -e '/,/{s/.*,[^0-9]*//;q};d')
    [ -n "$PID" ] && kill -USR1 $PID || true
end script

and this is '/etc/init/ufw.conf`:

# ufw - Uncomplicated Firewall
#
# The Uncomplicated Firewall is a front-end for iptables, to make managing a
# Netfilter firewall easier.

description     "Uncomplicated firewall"

start on net-device-added INTERFACE=lo
stop on runlevel [!023456]

console output

pre-start exec /lib/ufw/ufw-init start quiet
post-stop exec /lib/ufw/ufw-init stop

The latter file has a symlink in /etc/init.d:

$ ls -l /etc/init.d/ufw
lrwxrwxrwx 1 root root 21 2009-11-05 00:14 /etc/init.d/ufw -> /lib/init/upstart-job

Answer 2

look at this: http://www.cyberciti.biz/tips/how-do-i-run-firewall-script-as-soon-as-eth0-interface-brings-up.html the post-up command is what you are looking for i guess.

Here is more info on the files in /etc/network: https://serverfault.com/questions/81494/is-every-script-located-in-etc-network-if-up-d-when-an-interface-is-brought-up