DISCLAIMER
The material and methods reported in Linux Admin Smart Guide, even if tested, are provided without any guarantee. All the commands are run as privileged (root) user, so it is highly recommended to try them first on non-production machines and, in any case, to always do backups first. Linux Admin Smart Guide is not responsible for any damage or data loss caused by misformulated commands or inadvertently launched commands.
To gain a root shell, run the command sudo su -l from the shell of a regular user who is included in the sudoers list, or simply the command su -l and then providing the root password.