How do I start a service after the network is up?

Question

In my case, squid is started before DHCP has written a new /etc/resolv.conf which results in odd errors (timeouts, 504 Gateway) when I try to load a page in the web browser.

As I see it, the correct solution would be to start squid only after dhcpd/NetworkManager/whoever (?) has finished configuring the network.

Solution 1

You should modify the squid.conf file in /etc/init so that it only starts when network is up:

start on (started networking)

You can find much more info here, and looking at the files in your /etc/init/ dir.

This question should also help. If you prefer to configure it with a GUI, look here.

Solution 2

Here are two examples from the Upstart Cookbook:

To start a job when eth0 is available

start on net-device-up IFACE=eth0

To start once a non-loopback device has come up:

start on net-device-up IFACE!=lo

Note: net-device-up is not a regular job, it's an "Ubuntu well-known event".

Comments

[Javier Rivera]

Which Ubuntu version are you using?. Or more concrete, are you using SysV or upstart?.

[om123]

I'm on 11.10 and upstart.

[Javier Rivera]

Check: askubuntu.com/questions/21378/… or askubuntu.com/questions/3341/is-there-any-gui-tool-for-upsta‌​rt