Monday, July 20, 2015

Using Snappy Ubuntu Core to test-boot anything

Lab-As-A-Service Inception OS

Today morning I realized that it is quite possible to use chain-loading to boot into a test OS from within a Snappy Ubuntu Core system. I've decided to try to implement that and you can give it a try now. LAAS inception 0.1 [snap].

Update: I uploaded an older, broken version, please make sure you have this version installed:
a1bc56b7bc114daf2bfac3f8f5345b84  laas-inception_0.1_all.snap

Inception OS is a small Ubuntu Snappy Core-based system with a one more snap for programmatic control over boot process. Using the inception OS, any x86 or amd64 system (both in UEFI and legacy bios mode) can be converted into a remotely controlled web API that lets anyone reflash the OS and reboot into the fresh image.

The system always reboots into the Inception OS so this can be used to run unreliable software as long as the machine can be power-cycled remotely (which seems to be a solved problem with off-the-shelf networked power strips).

Installing the Inception OS

  1. Get a laptop, desktop or server that you can run Snappy Ubuntu Core on enough so that you have working networking (including wifi if that is what you wish to use) and working storage (so that you can see the primary disk. In general, the pre-built Snappy Ubuntu Core for amd64 can be used on many machines without any modification.
  2. Copy the image to a separate boot device. This can be a USB hard drive or flash memory of some sort. In my case I just dd'ed the uncompressed image to a 8GB flash drive (the image was 4GB but that's okay).
  3. Plug the USB device into your test device.
  4. In the boot loader, set the device to always boot from the USB device you just plugged in. Save the setting and reboot to test this.
  5. Use snappy-remote --url=ssh:// install-remote laas-inception*.snap to install the Inception snap.
  6. SSH to the test system and ensure that laas-inception.laas-inception command exists. Run it with the install argument. This will modify the boot configuration to make sure that the inception features are available.
  7. At this stage, the device can be power-cycled, rebooted, etc. Thanks to Snappy Ubuntu Core it should be resilient to many types of damage that can be caused by rebooting at the wrong moment.

Installing Test OSes

To install any new OS image for testing follow those steps.
  1. Get a pre-installed system image. This is perfect for snappy (snappy-device-install core can be used to create one) and many traditional operating systems can be converted to pre-installed images one can just copy to the hard drive directly.
  2. Use ssh to connect to the Inception OS. From there you can download and copy the OS image onto the primary storage (hard drive or SSD) of the machine. Currently this is not implemented but later versions of the Inception OS will simply offer this as a web API with simple tools for remote administration from any platform.
  3. Use the laas-inception.laas-inception boot command to reboot into the test OS. This will restart the machine and boot from the primary storage exactly once. As soon as the machine restarts or is power cycled you will regain control as inception OS will boot again.

How it works

Inception OS is pretty simple. It uses GRUB chain-loading to boot anything that is installed on the primary storage. It uses a few tricks to set everything in motion but the general idea is simple enough that it should work on any machine that can be booted with GRUB. The target OS can be non-Linux (inception can boot Windows, for example, though reboots will kick back into the Inception OS).

No comments:

Post a Comment