How to avoid and forbid direct root connections by locking the root password and to force specified users to gain root access with sudo. The first step is to install sudo and to allow its usage with the named user. Given that all connections will only be allowed by SSH, and only using a key-pair authentication (no password), the user will have no defined password and will need a passwordless access to the root account.


Create new variables

We need to define the named user who will be allowed to gain root access. We need the username UN and the user password UP. Lets add them to the configuration file :

cat << EOF >> /root/config.env
export UN="`grep 1000 /etc/passwd | cut -d: -f1`" # Named user name
export UP="`grep 1000 /etc/passwd | cut -d: -f1`" # Named user password

Tune the default values

The variables are initialized with default values. You need to read them, check them, fix them, tune them, with your prefered text editor (vi, isn’t it ?)

vi /root/config.env

Load the variables in the environment

source /root/config.env


Let’s install sudo.

apt-get install -y sudo

Named user configuration

Allow the named user to run any command, with password. At this stage, the user still has a password-protected account. Password login will be disabled after the SSH configuration.


adduser ${UN} sudo

Allow user to run any command without password (he will have password disabled later)

echo "${UN} ALL=(ALL:ALL) NOPASSWD: ALL" > /etc/sudoers.d/${UN}