Sudo Not Installed?
The fix – getting sudo to work – is at the bottom.
When you use Debian for the first time, you may have quickly run into this:
bash: sudo: command not found
This happens if, during the setup process, you provide a root password. The Debian installation will install sudo if you do not specify the password.
Notice, in the last paragraph of the above dialog:
If you leave this empty, the root account will be disabled and the system’s initial user account will be given the power to become root using the “sudo” command.
And, here is a relevant portion from the installation guide for Debian 8 Jessie:
By default you are asked to provide a password for the “root” (administrator) account and information necessary to create one regular user account. If you do not specify a password for the “root” user this account will be disabled but the sudo package will be installed later to enable administrative tasks to be carried out on the new system.
So, if you do specify the password for the root user account, the sudo package will not be installed.
To add sudo, all you need to do is:
1. Open a terminal and change to root
2. Install sudo
apt install sudo
3. Add user to sudo group
usermod -a -G sudo matthew
4. Have the user log out and back in.