How to Fix “Username is not in the sudoers file. This incident will be reported” in Ubuntu
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mount -o remount,rw /
mount --all
chown root:root /usr/bin/sudo
chmod 4755 /usr/bin/sudo
shutdown -r now
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In Unix/Linux systems, the root user account is the super user account, and it can therefore be used to do anything and everything achievable on the system.
However, this can be very dangerous in so many ways – one could be that the root user might enter a wrong command and breaks the whole system or an attacker gets access to root user account and takes control of the whole system and who knows what he/she can possibly do.
Based upon this background, in Ubuntu and its derivatives, the root user account is locked by default, regular users (system administrators or not) can only gain super user privileges by using the sudo command.
And one of the worst things that can happen to a Ubuntu System admin is losing privileges to use the sudo command, a situation commonly referred to as “broken sudo”. This can be absolutely devastating.
A broken sudo may be caused by any of the following:
A user should not have been removed from the sudo or admin group.
The /etc/sudoers file was altered to prevent users in sudo or admin group from elevating their privileges to that of root using sudo command.
The permission on /etc/sudoers file is not set to 0440.
