Ubuntu Admin User Add
How to Create a SuperUser/Amdin User on Ubuntu GNU/Linux – Step by step Tutorial.
Especially Relevant: this is the right procedure to follow Only in Case you do Not Dispose of Any SuperUser on System!
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Reboot your Ubuntu System.
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On GRUB Splash Select > Boot in recovery mode.
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Select > Drop to root Shell.
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Create SuperUser with Admin Privileges.
adduser [myUser]
Choose a Passowrd for your New User.
Then to Add User into the sudoers Group do:adduser [myUser] sudo
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Finally, Reboot your Ubuntu System.