ALAR

Azure Linux Auto Recover

Azure Linux Auto Recover (ALAR) is a tool to assist with the most common issues to boot a Linux based VM. ALAR is designed to be used on the CLI from another Azure based Linux VM, in order to recover the OS disk from a VM which had a boot issue. It can also be used together with 'the az vm repair' extension to automate most of the VM repair creation.

The scenarios the tool can assist you are:

• malformed /etc/fstab
  • syntax error
  • missing disk
• damaged initrd or /boot/grub/grub.cfg is missing the right setup
• last installed kernel is not bootable
• serial console and grub serial are not configured well
• GRUB/EFI installation or configuration damaged
• Disk full causing a non-boot scenario, specifically related to auditd configurations.

It has also the following features

• does support ADE. Either by decrypting the device, to be recovered, automatically or with the help of an ADE encryption key passed over to the tool: --ade-password <password>
• A custom recover disk path can be specified if LUN0is already occupied: --custom-recover-disk
• By default all action scripts are incorporated into the ALAR tool. This can be of help if no access to the internet does exists. Though, if required the action scripts can be downloaded with the help of the flag --download-action-scripts this may be handy if a new action is available or an existing one got improved.
• A special action chroot-cli allows to fix things manually if the available action scripts aren't of the right choice. All things get setup automatically. The user gets automatically placed in a terminal belonging to the associated chroot session. This option can't be used together with 'az vm repair run'

What actions are available

fstab

This action does strip off any lines in the /etc/fstab file which are not needed to boot a system. It makes a copy of the original file first. So, after the start of the OS the administrator is able to edit the fstab again and correct any errors which didn’t allow a reboot of the system before. This action provides the following additional functionality.

• If device names are found they get translated to an UUID identifier
• If '/boot' or '/boot/efi' is missed it/they get added to the fstab configuration
• The resource disk configuration isn’t removed

kernel

This action does change the default kernel. It modifies the configuration so that the previous kernel version gets booted. After the boot the admin is able to replace the broken kernel.

initrd

This action corrects two issues that can happen when a new kernel gets installed

1. The grub.cfg file is incorrect created
2. The initrd image is missing or corrupt

serialconsole

This action enables both the serialconsole and the GRUB serial. Incorrect vaules get overwritten by a set of defaults The correct setup allows you to see the GRUB Menu as well get access to the system via the Azure Serial Console.

grubfix

This action is reinstalling GRUB and regenerates the grub.cfg file

efifix

This action is reinstalling the required software to boot from a GEN2 VM. The grub.cfg is regenerated as well.

auditd

This action will alter the auditd configuration, replacing any HALT directives in the /etc/audit/auditd.conf file. Also in LVM environments, if the volume containing the audit logs is full, and free space is available in the volume group, the logical volume will be extended by 10% of the current size.

How to use ALAR

ALAR can be used either from the CLI of an existing Azure VM or with the help of the vm-repair extension for the Azure CLI tool.

From a SHELL prompt

In the simplest form: alar <action-name> i.e. alar fstab If a specific disk and the ADE disk-encryption key is required: alar <action-name> --custom-recover-disk <disk> --ade-password <key> i.e. # alar initrd --custom-recover-disk /deV/sdd --ade-password "password in base64 format"

From the Azure CLI

Utilizing ALAR with the help of the Azure CLI is quite simple. Create at fist a recover VM. We assume your VM named suse15 in the resource-group az vm repair create --verbose -g suse15_group -n suse15 --repair-username rescue --repair-password 'password!234'

In the next step the run command option is used to execute ALAR on the repair VM created before.

`az vm repair run --verbose -g suse15_group -n suse15 --run-id linux-alar2 --parameters initrd --run-on-repair`

As a final step the restore command is used az vm repair restore --verbose -g suse15_group -n suse15

Detailed information about the vm-repair extension is documented at https://learn.microsoft.com/en-us/cli/azure/vm/repair?view=azure-cli-latest

What to do if more than one ACTION is require?

If more than one action has to be applied this is possible as well. Pass over both to ALAR separated by a comma i.e. ‘fstab,initrd’

NOTE No spaces allowed!

LICENSE

Licensed under either of

• Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
• MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)