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How do I edit an invalid sudoers file? It throws the below error and it's not allowing me to edit again to fix it.

Here is what happens:

$ sudo visudo
>>> /etc/sudoers: syntax error near line 28 <<<
sudo: parse error in /etc/sudoers near line 28
sudo: no valid sudoers sources found, quitting

15 Answers 15

412
+50

On a modern Ubuntu system (and many other GNU/Linux distributions), fixing a corrupted sudoers file is actually quite easy, and doesn't require rebooting, using a live CD, or physical access to the machine.

To do this via SSH, log in to the machine and run the command pkexec visudo. If you have physical access to the machine, SSH is unnecessary; just open a Terminal window and run that pkexec command.

Assuming you (or some other user) are authorized to run programs as root with PolicyKit, you can enter your password, and then it will run visudo as root, and you can fix your /etc/sudoers.

If you need to edit one of the configuration files in /etc/sudoers.d (which is uncommon in this situation, but possible), use pkexec visudo -f /etc/sudoers.d/filename.

If you have a related situation where you have to perform additional system administration commands as root to fix the problem (also uncommon in this circumstance, but common in others), you can start an interactive root shell with pkexec bash. Generally speaking, any non-graphical command you'd run with sudo can be run with pkexec instead.

(If there is more than one user account on the system authorized to run programs as root with PolicyKit, then for any of those actions, you'll be asked to select which one you want to use, before being asked for your password.)


If that doesn't work--for example, if there are no users authorized to run programs as root via PolicyKit--then boot from an Ubuntu live CD (like the CD you probably used to install Ubuntu) and mount the filesystem for the installed system. You can do this by running sudo parted -l to view your partitions--there is probably just one ext4 partition, and that's the root filesystem.

Suppose the installed Ubuntu system's root filesystem is on /dev/sda1. Then you could mount it with sudo mount /dev/sda1 /mnt. Then you can edit the installed system's sudoers file with sudo nano -w /mnt/etc/sudoers. Or, even better, you can edit it with

sudo visudo -f /mnt/etc/sudoers

(which will prevent you from saving a sudoers file with incorrect syntax).

| improve this answer | |
  • 7
    pkexec /usr/sbin/visudo worked on debian 7 – marinara Mar 5 '14 at 1:33
  • 11
    HOLY COW! Thanks a LOT! Saved my bacon. Added a file as suggested into etc/sudoers.d/ directory USING A REGULAR TEXT EDITOR (D-O-N-T__D-O__T-H-A-T!!!). Lost all ability to do elevated privileges, INCLUDING, editing the offending file. This helped edit the file. Weird though, I had to edit /etc/sudoers first, then it found the errors in the other file and opened that for me. EVEN WEIRDER, the directive in /etc/sudoers file 'inlcudedir /etc/sudoers.d' was commented out, and it still includes it. – Dennis Apr 5 '15 at 3:15
  • 5
    @Dennis Somewhat confusingly, #include directives in sudoers files are treated specially; the leading # does not cause the rest of the line to be interpreted as a comment, in that case. As man sudoers says: "The pound sign (‘#’) is used to indicate a comment (unless it is part of a #include directive or unless..." See also visudo: #includedir sudoers.d (archived from lzone.de/blog). – Eliah Kagan Apr 5 '15 at 3:49
  • 6
    My user is sudoer but i got this error: Error executing command as another user: Not authorized – SuB Oct 30 '16 at 10:05
  • 4
    In Ubuntu 16.04, pkexec visudo asks for a password, which does not accept the correct password. It throws an "AUTHENTICATION FAILED" error. – Juha Untinen Aug 14 '18 at 9:30
63

Always use visudo to edit your sudoers file, never edit it directly yourself. It will prevent you saving it to disk unless it validates.

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  • 26
    hindsight is 20/20 – code_monk Jan 9 '15 at 1:57
  • 8
    It won't prevent disaster. It's easy enough to validly deny yourself. – Joshua Oct 5 '15 at 22:02
  • Can visudo be used by scritps? If so, how? – Lukas Jul 7 '16 at 15:01
  • I don't have visudo installed. So I did pkexec vim. Then it shows the list of users and asks for password. When I provide password, it throws error as " Error executing command as another user: Not authorized". Please help – Shyamkkhadka May 24 '18 at 5:48
29

Type in:

pkexec visudo

Then change last line

#includedir /etc/sudoers

To:

#includedir /etc/sudoers.d

It should solve your problem.

| improve this answer | |
  • 2
    I've noticed that removing the leading # from #includedir causes syntax errors, the # is part of the directive, at least on Ubuntu 12.10. – SAFX Apr 5 '13 at 2:46
  • 1
    That just saved me a lot of headache. Thanks a ton :) – Addo Solutions Jul 16 '17 at 18:29
  • 2
    I don't have visudo installed. So I did pkexec vim. Then it shows the list of users and asks for password. When I provide password, it throws error as " Error executing command as another user: Not authorized". Please help – Shyamkkhadka May 24 '18 at 5:48
13

if anyone else like me didn't have pkexec installed, or was not able to run vi, visudo, nano or any other editor to change sudoers file you can be sure with this process.. I was saved with this:

  • reboot
  • hold shift key while booting to have option for recovery mode (enter it)
  • enter command line as root (second last option at my grub menu)
  • remount boot device for rw, and apply exec right for user, and edit file

    mount -n -o remount,rw /
    chmod u+x /etc/sudoers
    visudo /etc/sudoers
    

fix that mistake and be happy :)

| improve this answer | |
  • While pkexec solution suggested by @eliah-kagan seems to be easier, this one is more universal. On my machine it turned out that there is no pkexec installed and of course I could not install it because sudo apt-get install pkexec somehow did not work. – running.t Oct 15 '15 at 14:06
  • Also within this approach I would use visudo instead nano /etc/sudoers. – pa4080 Dec 3 '18 at 12:38
6

If you 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

| improve this answer | |
  • Hi, does it removes the iptables, files of existing system ? – Shyamkkhadka May 24 '18 at 7:48
4

There is nothing wrong #include sudoer.d removing #include sudoer.d won't make any difference.

But please make sure you don't have any syntax errors. I had same issue but and spent hours to fix and just figured out they are syntax errors. Refer to manual and make them right.

For example Say your username is : dolly I used following which is wrong

 dolly ALL = (ALL) ALL NO PASSWD: ALL

correct syntax is

dolly ALL = (ALL) ALL //give permission to everything, not good

or

dolly ALL=(ALL) NOPASSWD:/usr/bin/thurderbird //good, give specific permission

hope this helps

| improve this answer | |
  • A better approach than making sure you don't have syntax errors is to always use visudo when editing these files, which makes sure you don't have syntax errors for you, before it modifies file. visudo is not just for editing /etc/sudoers--it will also create and edit files in /etc/sudoers.d. It will also work with whatever text editor you want. See the manpage for details. – Eliah Kagan Jul 3 '12 at 0:12
  • As for giving specific permission, please note that this is only useful for very simple commands/apps, because any sufficiently complex app (including thunderbird, which should never be run as root anyway) will effectively give the user full system access when run as root. Even seemingly simple functionality opens the door to full root access. For example, a user who can run a program that can save a file to an arbitrary location as root can gain full root access (they can install their own /etc/sudoers, or if syntax limitations prevent that, they can install their own /etc/crontab). – Eliah Kagan Jul 3 '12 at 0:16
3

run recovery mode then type this

chown -R root:root /etc/sudoers.d
chmod u=rwx,g=rx,o=rx /etc/sudoers.d/
chmod u=r,g=r,o= /etc/sudoers.d/*

only the group and user root should have read privelege

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2

You can also login as root on a tty console with Ctrl+Fn (Fn from 1 to 6) and run visudo.

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2
pkexec visudo

then revert your mistakes

| improve this answer | |
  • 1
    not necessary to use pkexec – Braiam Jan 1 '14 at 12:01
  • 1
    @Braiam visudo has to be run as root. If sudo doesn't work, pkexec sometimes does. This is covered by my earlier answer... but it is a correct answer, visudo by itself (when not run as root) will not work, and there may be value in correct, brief answers even when their recommendations overlap considerably with other answers. Of course, if one goes into recovery mode, that's a root shell and then neither sudo nor visudo is necessary for commands like pkexec. Maybe that's what you mean... – Eliah Kagan Mar 29 '14 at 5:30
1

You can edit your boot entry while in grub as well.

Simply reboot your pc, and wait for grub to show. Then press "e" on the "Ubuntu" entry to edit it.

Look for a line with "linux = " or "kernel = " and simply add an "single" to the end of that line.

Then press F10 to boot this temporarily modified boot entry. This will give you a shell (without GUI) with root rights and you can edit the sudoers file with s.th. like nano /etc/sudoers back to its previous state.

Then reboot and its done.

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1

In Ubuntu 16.04 running on a VirtualBox (shouldn't make a difference), the above methods didn't work for me (invalid row in the end of the file). What did work was:

  1. Restart the VirtualBox
  2. Let it boot normally, until it asks for your username & password in the console
  3. Login normally with your username
  4. Then when you end up in the console (provided your box doesn't boot into a GUI), simply give the command su - and then give your own username's password.
  5. It should now end up in root@ubuntu-xenial:~# prompt, if the /etc/sudoers isn't too broken or empty. Not sure what would happen in that case.
  6. Then you can simply run visudo and fix the file.
  7. Then Ctrl + X and it will prompt to Save modified buffer. Press Y and Enter
  8. Restart the box and it should work now.

In case your /etc/sudoers is empty or missing something, and you can edit it, then here's the contents of mine:

Defaults env_reset
Defaults mail_badpass
Defaults secure_path="/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/snap/bin"

root ALL=(ALL:ALL) ALL

%admin ALL=(ALL) ALL

%sudo ALL=(ALL:ALL) ALL
| improve this answer | |
  • Your step 4 does not make sense, it only works when your root password is same as your normal user. – alfred Aug 3 '19 at 12:47
  • Which is very common in a local VM. – Juha Untinen Aug 3 '19 at 16:37
1

Good practice: a backup terminal window and run sudo su there. On another termianl run visudo or sudo vim /etc/sudoers. If anything goes wrong, go back to terminal one and fix the file. You may ask, why not just run sudo su before visudo in one terminal? This works as well, but has higher risk of you closing the terminal before you know it.

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1

Adding this for the new wave of WSL-based Linux VMs. When I locked myself out of my debian-based WSL2 VM (Pengwin) which didn't have pkexec and the root password was not set, here's what I found fixed the problem:

  • Open a Windows Powershell as administrator (right-click 'Run as Administrator')
  • Set the default user on the VM to be root (because it won't ask for a password) per this how-to:
<distro.exe> config --default-user root

Example:

ubuntu1804.exe config --default-user root 

or

pengwin.exe config --default-user root
  • Re-launch your distro.
  • You should now be root and can go fix your sudo problem.
  • Repeat the process to set the default user back to normal.
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0

There is a way simpler solution. Without rebooting, recovery mode, or pkgexec (pkgexec didn't work and have no idea why or how I should use it), simply do:

su root # switch to root user, without using sudo (which is broken at this point)
your_favorite_editor /etc/sudoers # e.g. nano

And then just fix the syntax error!

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  • 1
    What's with the downvote? Worked perfectly for me. – rien333 Aug 8 '19 at 13:29
  • This answer is actually working. I wonder why the downvote !! – McLan Nov 25 '19 at 18:48
  • I suggest that downvote should come with an explanation. Otherwise, people can exploit it and, even worse, disallow a valid answer. – McLan Nov 25 '19 at 18:50
  • I think the downvote came from the land that running this command requires root to have a password, which by default it doesn't. – Ali Tou May 20 at 0:07
  • Ah, so the thing is that it doesn't work for ubuntu. So many questions on this board are applicable to linux in general, however, that I often fail to think about distro differences (and of course, this is the main thing that comes up on google when you search this problem). – rien333 May 20 at 8:44
0

When this happens to a non-GUI system (your production server, maybe) the pkexec fails with this error message:

polkit-agent-helper-1: error response to PolicyKit daemon: GDBus.Error:org.freedesktop.PolicyKit1.Error.Failed: No session for cookie
==== AUTHENTICATION FAILED ===
Error executing command as another user: Not authorized

In this situation, using pkttyagent can be helpful. If you want to remove a corrupted file in sudoers.d directory, use this:

pkttyagent -p $(echo $$) | pkexec rm /etc/sudoers.d/FILENAME

If you want to recover the default /etc/sudoers, you can use this gist to copy the default configurations, putting it in a non-root accessed place (e.g. your $HOME). Then, you can overwrite your sudoers file:

pkttyagent -p $(echo $$) | pkexec cp ~/sudoers /etc/sudoers

NOTE: Using this approach, after running your command, probably your access to the shell will be gone. But I'm sure losing one shell session is much better than losing your server! (According to the manpage, this is the normal behavior: When its services are no longer needed, the process can be killed.)

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