Dell Inspiron 15" laptop I installed Ubuntu 12.04.2 (because that fit on a CD, part of me hates using up a whole DVD over a couple of MB!) Everything worked. I used the software update button, it installed a bunch of stuff, and everything worked. I was trying to get my CAC working and installed the drivers for the IOGear GSR202 smart card reader and cackey. That wasn't working, and a couple of people thought coolkey worked better so I went to install that. At some point, I did an apt-get update / apt-get upgrade. After rebooting, my Wi-Fi network is gone, and the icon is gone from the bar at the top.

I've Googled. Lots of suggestions talk abouy uninstalling / reinstalling stuff. Others wind up referring to network-manager-gnome things. That isn't installed, and so isn't how this worked in the first place. I can't find any other control panels that have anything to do with networking. 'ifconfig wlan0 up' doesn't result in anything. When I open System Settings, Network, there's a message that says "The system network services are not compatible with this version". Huh? A few references to that being an issue from over a year ago.

So... how do I go about getting my wireless working again?

Is your wireless card a Broadcom?
output and see if so, down towards the end.
More hardware info helps.

I'll check when I get home. But this isn't a hardware issue… the wireless worked just fine before the update. This is almost certainly going to be a software issue. How would I go about finding out what driver is being used? Or if it's a kernel issue?

you mention network-manager-gnome not being installed. If I recall correctly, it should be, as its the default network-manager for ubuntu.

lspci identifies my wireless card as a Qualcomm Atheros AR9285

dpkg --get-selections shows network-manager-gnome as "deinstall" (I don't know if that means it's installed and can be deinstalled, or if it means it is not installed). dpkg --listfile network-manager-gnome shows /etc/xdg/autostart/nm-applet.desktop

I thought the Ubuntu wm was Unity, not Gnome? Can I find out if a package was installed but removed? This did work before. I know, famous last words...

look in the sofware center and search for network-manager-gnome. it should show as installed if its present.

ubunutu uses a lot of gnome tools with unity, including the file manager, gedit, the terminal, and a bunch of other stuff. Once upon a time unity was based on gnome (3?)

Thanks, all.

Turns out that something had uninstalled network-manager, AND somehow the wifi got turned off. Once I dug out an Ethernet cable, I reinstalled network-manager, could then run nm-tool, and got to rfkill showing it hard disabled. Weird!