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up vote 3 down vote favorite

I want to login as root, but when I enter 

sudo -s

and enter password, this message is shown: "you are not in sudoers file", and when I enter 

su

and enter password, this is shown: "authentication failure".

My os has one account only. about past1 hours ago I log on as root and do some commands , when I logout , I can't login another time!

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We'd need to know what commands you ran when you were root. You might need to reset your password: askubuntu.com/questions/24006/… – Jorge Castro Dec 31 '11 at 21:47

2 Answers

up vote 2 down vote accepted

The su command requires you to put in root password. Root user on Ubuntu in general is locked so no user can login as root so su is not likely to work.

For sudo -s to work you will have to be part of the admin group on an Ubuntu machine, which apparently you are not.

If you are the only user on the system that is concerning and may be quite involved to fix. If not I would suggest you talk to the System Administrator or owner of the system to see if you even can get root privileges.

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2  
and if it is your machine, and you've somehow lost root privileges, you'll have to fix it by booting into recovery mode. – ams Dec 30 '11 at 20:19
My os has one account only. about past1 hours ago I log on as root and do some commands , when I logout , I can't login another time! – ava Dec 30 '11 at 20:28
What commands did you do? – Karlson Dec 30 '11 at 20:29
I don't know exactly. that was some simple commands such as changing umask – ava Dec 30 '11 at 20:32
and some shell programming, add group – ava Dec 30 '11 at 20:35
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up vote 0 down vote

The https://help.ubuntu.com/community/RootSudo is suggesting:

If you really need a persistent Root login, the best alternative is to simulate a Root login shell using the following command...

sudo -i

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doesn't work . My os has only one account – ava Dec 30 '11 at 20:29

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