Sometimes after waking from sleep, networking seems to fail on GalliumOS on my laptop.
Check status of
~ $ service network-manager status
If at the top it says
failed in red (or, basically anything other than
active (running) in green!) then
network-manager needs restarting. This should do the trick:
~ $ sudo service network-manager restart
network-manager seems to (sometimes?) crash the networking applet that sits in the Notification Area. (See bug report) If so, the network status icon will disappear from the Notificaiton Area.
nm-applet can be restarted as follows:
~ $ killall nm-applet; nm-applet & disown
(based on comment #5 on the bug report above, and other ideas from SuperUser.com)