114

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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2
  • 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
    Commented Dec 31, 2011 at 21:47
  • Do you want to change user in terminal as you used su command? if you want to then you need to have the root password
    – Jatttt
    Commented Mar 5, 2014 at 14:45

4 Answers 4

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81

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 thus 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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12
  • 10
    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
    Commented Dec 30, 2011 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
    Commented Dec 30, 2011 at 20:28
  • What commands did you do?
    – Karlson
    Commented Dec 30, 2011 at 20:29
  • I don't know exactly. that was some simple commands such as changing umask
    – ava
    Commented Dec 30, 2011 at 20:32
  • 1
    This link explains how to fix sudo: psychocats.net/ubuntu/fixsudo
    – Steven C. Howell
    Commented Jun 12, 2015 at 20:22
80

Be aware that the root account is not active by default.

You will need to do:

sudo passwd root

Then go ahead to set password. Use the root user using

su root
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1
27

The https://help.ubuntu.com/community/RootSudo suggests:

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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1
  • 1
    doesn't work . My os has only one account
    – ava
    Commented Dec 30, 2011 at 20:29
7

First of all you need to have admin privileges. If you don't have admin privileges then while booting press and hold the shift key. You will enter the GRUB menu. Here select recovery mode. When you see the list of options like dpkg etc, choose to start a root shell and type:

adduser username sudo

(where username is your username :-) )

this will add you to the sudoers group! Then type exit and boot normally. when you enter your account, type:

sudo passwd root

Then enter your password and type the new root password

After that you can type su and enter the 'root' password.

If you don't want to change the root password then you can use:

sudo -i

to start a root shell, using your own password.

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2
  • Tell me if you want to activate the root account to log in the root account :)
    – Jatttt
    Commented Mar 5, 2014 at 14:57
  • Just a question, does the recovery mode, you mentioned above, will affect any pre-installed program in the Ubuntu?
    – Santosa Sandy
    Commented Jan 20, 2016 at 2:55

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