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I am getting this error:

sudo: parse error in /etc/sudoers near line 23
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

I was trying to disable password authentication so I don't have to type password every time I want to install something, but I probably changed it in a not very good way. I am a newbie to Ubuntu, I got sick of Windows :)

So far I've found some people suggesting booting in single user mode, but I'm afraid of messing things up more.

How can I fix this error?

Alaa Ali
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Robert Fáber
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  • If you boot in single user mode and use visudo, then it won't let you save an incorrect file, so you will not be able to mess things up further. – nanofarad Oct 30 '12 at 11:18
  • Thank you, how do I change the file, then? And, how exactly do I boot in single user mode? – Robert Fáber Oct 30 '12 at 11:19
  • Hold Shift immediately while booting so that you get the GRUB screen. Select the recovery mode. Choose to drop to a root terminal. Run mount -n -o remount,rw / and then visudo. Ctrl+O saves, Ctrl+X exits without saving. It won't let you save a bad file. – nanofarad Oct 30 '12 at 11:21
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    @ObsessiveSSOℲ it would be nice to convert the comment to answer and let the questioner to mark it as the best answer. For future - help - others I mean. – NickTux Oct 30 '12 at 12:14
  • Deactivating that password switch is about as bad as deactivating UAC on Windows. Every command that tries so call sudo internally can do without any problems. You could easily have some software (rootkit) installed without you knowing. I would strongly discourage doing this in the first place. – Martin Ueding Oct 30 '12 at 12:35
  • I know, I know, it was a huge mistake. Thank you all for your answers. – Robert Fáber Oct 30 '12 at 22:12
  • This is a statement, not a question. – psusi Sep 15 '13 at 01:38
  • @psusi and close voters: huh? It's a question, with proper answers. It's just missing a "how can I fix this error" sentence, which I've just added. There's no need to close it. – Alaa Ali Sep 15 '13 at 17:46
  • @Alaa, it says this is what happened, and this is what I have already been told to do to fix it. That's not a question. – psusi Sep 15 '13 at 18:26
  • @psusi when problems are questions? He is asking how to revert it back, and is giving us the history of his actions, he describe his problems, he got a solution. Why close it? – Braiam Sep 16 '13 at 00:22
  • @Braiam, because the "solution" is in the "question". Without knowing why that isn't acceptable ( besides "I'm afraid" ) it isn't possible to provide a real answer. – psusi Sep 16 '13 at 01:36
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    On newer Ubuntu distributions, there's a simple solution (not requiring any reboot nor recovery), described here: http://askubuntu.com/a/73872 –  Aug 28 '14 at 11:23
  • Isn't there already an answer http://askubuntu.com/questions/73864/how-to-modify-a-invalid-etc-sudoers-file-it-throws-out-an-error-and-not-allowi actually. Just type pkexec visudo – xji Apr 03 '15 at 10:18

6 Answers6

62

Fixing this is dead simple, and it is answered elsewhere on askubuntu.

Short answer, use:

pkexec editor_of_choice
Community
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NeilenMarais
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    This is definitely the simplest and best answer. I had no clue pkexec existed. Thanks a lot both – Bizmate Apr 14 '16 at 17:05
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    When I do pkexec, it gives list of users to authenticate. When I type password, it gives Authentication failure. Please help. – Shyamkkhadka May 24 '18 at 05:44
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    @Shyamkkhadka I ran into this also. This solution on GitHub saved me and about a hundred other people. – gillytech Feb 19 '20 at 18:49
  • This didnt work for me with an error " No session for cookie " but I did this in two terminals: In the first terminal run the following command to get its PID.

    echo $$

    In the second terminal run

    pkttyagent --process PID_FROM_STEP_1

    Then you can run "sudo pico /etc/sudoers" or whatever you want in first terminal, and the second terminal will ask for user password. and will work

     – DefToneR May 04 '21 at 21:08
  • thx, useful compare to reboot in recovery mode red-tape procedures... https://stackoverflow.com/a/58195402/3806250 and https://stackoverflow.com/a/58199760/3806250 – Rγσ ξηg Lιαη Ημ 雷欧 Jan 14 '22 at 18:36
  • Using pkexec directly didn't work for me (didn't accept password), but strangely enough @Shyamkkhadka solution using 2 terminals worked! – pakman Nov 22 '23 at 16:19
19

Hold Shift immediately while booting so that you get the GRUB screen. Select the recovery mode. Choose to drop to a root terminal. Run mount -n -o remount,rw / and then visudo. It'll let you fix your problems with the file and save. It won't let you save a malformed file.

nanofarad
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4

Folowing solution is for remote servers, it works!

http://ubuntuforums.org/showthread.php?t=2036382&p=12144840#post12144840

then just use visudo to add wheel, etc

  1. Rename your current file

    mv /etc/sudoers{,.bak}

  2. Create a new one vi /etc/sudoers with the following basic content:

    # /etc/sudoers
#
# This file MUST be edited with the 'visudo' command as root.
#
# See the man page for details on how to write a sudoers file.
# Defaults    env_reset
# Host alias specification
# User alias specification
# Cmnd alias specification
# User privilege specification
root    ALL=(ALL) ALL
# Allow members of group sudo to execute any command after they have
# provided their password
# (Note that later entries override this, so you might need to move
# it further down)
%sudo ALL=(ALL) ALL
#
#includedir /etc/sudoers.d
# Members of the admin group may gain root privileges
%admin ALL=(ALL) ALL

  3. Run visudo and add your custom stuff.

Kevin Bowen
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Igor Parra
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2

If u messed up your sudoers file.You'll need to:

  • Reboot into recovery mode (hit escape during boot, choose the recovery mode option on the grub screen)
  • Choose the 'Enable networking' option (if you don't your filesystem will be mounted as read-only. who knew)
  • Chosee the 'Drop to root shell' option
  • run visudo, fix your file
  • Reboot with normal grub option

source :- http://mario.net.au/content/recover-etcsudoers-ubuntu-1204

streak
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    Follow up question: When I choose the Enable networking option, I'm prompted to tell the system that I'm sure. I do that and I just drop into nothing. No root prompt, nothing. What should I expect to see/do after the 2nd step? Thanks. – Rob Wilkerson Jan 23 '13 at 14:25
2

You can do this:

Create a copy

cp /etc/sudoers /etc/sudoers.bak

Edit problem parts there

vim /etc/sudoers.bak

Replace the origin sudoers file

cp /etc/sudoers.bak /etc/sudoers

It works for me.

ajile
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1

I screwed up the sudoers file to find out that I don't remember the root password. Solution: rebooted under Windows (I have a dual boot) and edited the file using ext2fsd (you have to reboot after the installation). In principle, this could be another Linux or a live flash, not necessarily Windows.

18446744073709551615
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  • A lot of people dual-boot Windows and Ubuntu, so this is a solid approach! I know been a while since you've posted this answer... but might you be willing to [edit] this to expand it with detailed information about specifically how to set up and use ext2fsd for this purpose? – Eliah Kagan Jan 09 '17 at 01:29