Fix gnome authentication failure

readme.md

This is a known bug in gnome (ubuntu 18.04) : https://wiki.ubuntu.com/DebuggingScreenLocking#line-184

1. Check /etc/shadow permissions

# example
$ ls -l /etc/shadow
-r-------- 1 root root 1695 sept.  4 11:37 /etc/shadow

# should be
-rw-r----- 1 root shadow 1241 2010-08-22 12:43 /etc/shadow

2. Fix permissions

$ sudo chown root:shadow /etc/shadow
$ sudo chmod 640 /etc/shadow

# You should have this
$ ls -l /etc/shadow
-rw-r----- 1 root shadow 1241 2010-08-22 12:43 /etc/shadow