Use `visudo` to make changes to /etc/sudoers.
I broke /etc/sudoers and now I can't run sudo to fix it
It's just like when you lock your keys in the car. If you have the policy kit utilities installed then you likely have a utility celled pkexec installed. This is like a lightweight sudo, sort of. So just edit your /etc/sshd-config file using pkexec and be on your way:
pkexec vim /etc/sudoers
If that doesn't work then you'll have to resort to rebooting the machine in singke user mode and edit /etc/sudoers as root.
NOPASSWD does not work
If you set the NOPASSWD option for a user or group in sudo and it does not seem to work then you most likely have the order of statements wrong. The last statement in a sudoers file wins. Don't forget the files imported from /etc/sudoers.d. For example, the following will not work if noah is also a member of the sudo group because the sudo group definition comes after and overrides the NOPASSWD option.
noah ALL=(ALL) NOPASSWD:ALL # Allow members of group sudo to execute any command %sudo ALL=(ALL:ALL) ALL
The fix is to define the noah user options after the sudo group.
# Allow members of group sudo to execute any command %sudo ALL=(ALL:ALL) ALL noah ALL=(ALL) NOPASSWD:ALL
Set timestamp timeout
The following sets the timestamp timeout to 30 minutes for the given username, noah.
The following sets the timestamp timeout to 30 minutes for all users:
Sometimes for scripting you want sudo authentication to be consistent. If sudo is going to ask for a password then it is preferable to have it ask every time rather than ask once and then not again unless a timeout is reached in which case it will ask again. This can be difficult to script for. It's easier just to expect the password every time. You can pass sudo an option, -k to clear the timestamp. Note that there is a similar -K option (capital K) which must be use alone without a command to be run. Also note that the NOPASSWD option will still override the -k option.
sudo -k id
Allow a specific user, noah to sudo without a password:
noah ALL=(ALL) NOPASSWD:ALL
Allow all users in the admin group to sudo without a password:
%admin ALL=(ALL) NOPASSWD:ALL