Check with 'mount' that / isn't mounted read-only. The best option is probably to set a root password by running 'passwd' as root user in recovery mode, and then to reboot in normal mode, log in as root, and add your user to the sudoers group.
Check with 'mount' that / isn't mounted read-only. The best option is probably to set a root password by running 'passwd' as root user in recovery mode, and then to reboot in normal mode, log in as root, and add your user to the sudoers group.