sudoers - Google Compute Engine - no access to root

Question

I have a Google Compute Engine VM instance with a Asterisk Server running on it. I get this message when I try to run sudo:

sudo: parse error in /etc/sudoers near line 21
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

Is there a password for root so I can try to change it there? Any suggestions on this?

Answer 1

It looks like you have manually edited the /etc/sudoers file so while you would normally have sudo access, due to the parse error, you won't be able to do this directly.

Here's how to fix this situation.

1. Save the current boot disk

• go to to the instance view in Developers Console

• find your VM instance and click on its name; you should now be looking at a URL such as https://console.cloud.google.com/project/[PROJECT]/compute/instancesDetail/zones/[ZONE]/instances/[VM-NAME]

• stop the instance

• detach the boot disk from the instance

2. Fix the /etc/sudoers on the boot disk

• create a new VM instance with its own boot disk; you should have sudo access here
• attach the disk saved above as a separate persistent disk
• mount the disk you just attached
• fix the /etc/sudoers file on the disk
• unmount the second disk
• detach the second disk from the VM
• delete the new VM instance (let it delete its boot disk, you won't need it)

3. Restore the original VM instance

• re-attach the boot disk to the original VM
• restart the original VM with its original boot disk, with fixed config

How to avoid this in the future

Always use the command visudo rather just any text editor directly to edit the /etc/sudoers file which will validate the contents of the file prior to saving it.

Answer 2

Since i bumped into this issue too, if you have another instance or any place where you can run with gcloud privileges, you can run:

gcloud compute --project "<project id>" ssh --zone "europe-west1-b" "<servername>"

I ran this on a server which had gcloud as root, so you login to the other box as root too! Then fix your issue. (if you don't have a box, just spin a micro up with the correct gcloud privileges) saves the hassle of disk stuff etc.

Answer 3

As you probably figured out this requires the /etc/sudoers file to be fixed. As nobody has root access to the instance, you will not be able to do this from inside the instance.

The best way to solve this is to edit the disk from another instance. The basic steps to do this are:

1. Take a snapshot of your disk as a backup (!)
2. Shutdown your instance, taking care not to delete the boot disk.
3. Start a new "debugger" instance from one of the stock GCE images.
4. Attach the old boot disk to the new instance.
5. In the debugger instance, mount the disk.
6. In the debugger instance, fix the sudoers file on the mounted disk.
7. In the debugger instance, unmount the disk
8. Shutdown the debugger instance.
9. Create a new instance with the same specs as your original instance using the fixed disk as the boot disk.

The new disk will then have the fixed sudoers file.

Answer 4

I ran into this issue as well and had the same issue Nakilon was reporting when trying the gcloud workaround.

What we ended up doing was configure a startup script that removed the broken sudoers file.

So in your metadata put something like:

#/bin/sh

rm "/etc/sudoers.d/broken-config-file"
echo "ok" > /tmp/ok.log

https://cloud.google.com/compute/docs/startupscript

Answer 5

It is possible to connect to a VM as root from your developers console Google Cloud Shell. Make sure the VM is running, start the shell and use this command:

gcloud compute ssh root@<instance-name> --zone <zone> [--project <project-id>]

where instance-name is found in the Compute Engine VM Instances screen. project-id is optional but required if you are connecting to an instance in a different project from the project where you started the shell.

You can then fix this and other issues that may prevent you from using sudo.

Answer 6

As mentioned in above comments, I am getting the same error like below in gcp VM.

sudo: parse error in /etc/sudoers near line 21
sudo: no valid sudoers sources found, quitting
sudo: unable to initialize policy plugin

To solve this

I have ssh to another vm and become root then I ran gcloud ssh command to our main vm (where you are getting the sudo error.)

gcloud compute --project "<project id>" ssh --zone "europe-west1-b "<servername>"

And BOOM!, now are login as root in the VM.

Now you can access/change the /etc/sudoers file accordingly.

I found this hack better than recreating vm/disks. Hope this helps to someone!

Answer 7

I got a Permission denied error when trying to ssh to the problem instance via gcloud. Using a startup script as mentioned above by @Jorick works. Instructions for it are here. You will have to stop and restart the VM instance for the startup script to get executed. I modified the script slightly:

rm -f /etc/sudoers.d/google_sudoers >& /tmp/startup.log

After the restart, launch an SSH session from the cloud console and check that you are able to view the file contents (with sudo more /etc/sudoers.d/google_sudoers for example). If that works your problem has been solved.