Comment 3 for bug 58509

Just for those meeting this problem, here is my procedure to login.
A better one would be to find which script sets /dev/null to crw------ just after boot!

After booting, when the login screen appears, I type Alt+Ctrl+F1 to get a console.
Then I login as user and:

$ sudo chmod a+rw /dev/null

Since I have a non us keyboard I have to remember the position for + and / on a us keyboard.

Then I return to the X screen with Alt+Ctrl+F7 and can login.