Instances on Exoscale are designed to boot from their direct attached SSD disk, also known as root disk. It can happen that during a major upgrade of the system or while modifying the partition layout or bootloader that the instance cannot boot normally anymore.

To that purpose, a Rescue Mode exists in order do get an access to the root disk of the machine by booting from a different source. The boot program used in this case is the open source project called Netboot and allows to start a variety of Linux, BSD , ISO images, specialized installers or utilities.

Rescue mode pre-requisite

As Rescue Mode is not a default operation, it requires:

  • a working exo command-line environment
  • access to your account API key
  • access to the Exoscale portal

Booting into Rescue Mode

To reboot in Rescue Mode, first start by shutting down your instance. This can be performed via the CLI or via the portal in the instance details:

    exo vm stop broken-vm

Then start the instance in Rescue Mode

    exo vm start --rescue-profile=netboot broken-vm

Start instance rescue mode

The instance will now boot the Netboot image.

Accessing the rescue mode

To access the rescue mode, launch the Exoscale portal and navigate to the instance detailed view. Once on the detailed view, click the OPEN CONSOLE button.

A new window will open and display the instance screen and the Netboot menu will appear:

Netboot rescue menu from console

Perfom the operation you require in the instance - those are outside of Exoscale support perimeter - and finally reboot your instance.

Once rebooted the instance will exit Rescue mode and try to boot from the root disk.

Booting from a custom ISO image

Through rescue mode, it is possible to boot an instance from an external ISO as long as the latter supports virtIO storage and network drivers. To do so, perform the following steps:

  • Tools -> Utilities
  • netboot.xyz tools -> Test Distribution ISO
  • Enter URL (e.g. http://centos.anexia.at/centos/7.7.1908/isos/x86_64/CentOS-7-x86_64-LiveGNOME-1908.iso to boot a CentOS Live CD).

Netboot_rescue_menu_from_console_iso_image

With this method a bare metal recovery is possible for example.

Perfom the operation you require in the instance - those are outside of Exoscale support perimeter - and finally reboot your instance.

Once rebooted the instance will exit Rescue mode and try to boot from the root disk.