How to modify a invalid /etc/sudoers file? It throws out an error and not allowing me to edit again

Question

How do I edit an invalid visudo file?

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

Answer 1

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

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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).

Answer 2

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

Answer 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

Answer 4

I found the bug. It is in the last two lines of the default /etc/sudoers file. Remove the following entries from the end of the /etc/sudoers file with visudo.

#includedir /etc/sudoers.d

Answer 5

check permissions of root system /. it must be owned by root und use 755, than find command of sudo will find the config.

Answer 6

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

Answer 7

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

Answer 8

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.

Answer 9

Type in:

pkexec visudo

Then change last line

includedir /etc/sudoers

To:

includedir /etc/sudoers.d

It should solve your problem.

Answer 10

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