Azure Linux VM -How to recover from an fstab issue.

Hello All , On todays senario we will cover how to recover an fstab issue.

As you all probably faced that common issue that adding a new mount /line to fstab and forgot to check mount -a and once you boot your VM it is not coming up.

At On -premise it’s easy when you have access to the console / VMware / Hyper-V . you may use Single mode or any Live CD to recover fast.

First make sure you have entered once after every VM creation to the serial console and created a root password.
Recovery console required root password.

Until March 2018 on Azure Linux VM’s if you faced that issue [fstab] then you had to create a New VM as a rescue VM deleted you OS / or Clone that Os Disk mount it the the rescue VM make the proper changes and rebuild / switch with the healthy Os Disk.

Serial console is a great option for fast recovery. it allows you to reach your VM via serial port that means you can reach your VM even if your Network is down to repair \fix any boot \network\firewall\file system issues.

Demo:

I have a Centos 7.5 where i have added an fake mount to a VM that doesn’t exist.

this prevents my VM to boot unless i have used some fstab parameters to ignore that mount.

View from Azure Portal

and I have reboot the VM for this scenario to cause an fstab issue.

below from the Azure portal Serial console blade we can see that the VM is not able to complete the boot and dropped to emergency mode!

How can we fix it quickly ?
First make sure you have created a root password.
Recovery console required root password.

Enter your root password and this will drop you into console mode.

Long recovery

You will need another VM for recovery.

Delete the VM facing the issue From the Portal.[this won’t delete the disks]

wait around 5-10 minutes then navigate to another VM in the same region & using the same disk type [manged disk or STD or Premium] then attach the disk to that VM mount edit ad detach