My own daily use computer is a Lenovo Thinkpad T440s and I have installed only a Debian Linux distribution, in particular the testing version, this means that usually I have to solve by myself tipical problems that the stable distribution doesn’t have. Here I am including a list of those problems that I was able to solve, maybe alone maybe with the help of several forums in internet.
December 2015: iwlwifi
In Dec-2015 there were an update of the non-free package that control the intel wifi card ensembled on the Lenovo T440s, however the update broked my internet wifi conection. Here you have several steps to solve the problem:
A first step is try to see what is happening:
When this command is used we detect that Debian is trying to find a file named: iwlwifi-7260-7.ucode and looking on the webpage of debian concerning T440s we realize that the Network Controller,
In my case the documentation about T440s is not including this information but T440p that is basically the same laptop covers all the steps for Debian installation Debian-T440p. Another source of information is ThinkWiki.
Our first guess is a problem with iwlwifi, so simply we check the files installed by this debian package. You can find this information on the link: FileList-iwlwifi. We can realize that the iwlwifi-7260-7.ucode is not in the list of files installed. We can double check this with
Solving the problem
Now we can check the stable equivalent package at Stable-version-iwlwifi and confirm that iwlwifi-7260-7.ucode is there. Therefore simply download here the files on this package firmware-nonfree_0.43.tar.gz. Wa can extract the file named iwlwifi-7260-7.ucode-22.214.171.124 and copy at /lib/firmware with the name iwlwifi-7260-7.ucode. You can simply reboot the machine and the wifi is alive again.