Guix System on a GCE VM -- Success

[elaexuotee]

Attached is a minimal system configuration I have used to successfully
create a virtual machine instance on Google's Compute Engine (GCE).

The stock QEMU image [1] fails to boot under GCE, and since there is some past
interest [0], I figure it may be helpful to share the salient issues and how I
deal with them in the config.scm.

The boot problem fix boils down to this:

    (initrd-modules (cons "virtio_scsi" %base-initrd-modules))

Referencing Google's documentation on operating system requirements [2], we see
that their VMs run with Virtio-SCSI controllers; however, it just so happens
that the corresponding kernel module, virtio_scsi, is not included in the
initrd by default. Would it make sense to change this default?

That should be enough to get a working GCE instance running, provided you
follow Google's requirements for importing custom images [3]. It's not
challenging, but it takes time to familiarize oneself with GCE and the
associated toolchain.

To simplify the process I created a script capable of setting up a GCE instance
from a local qcow2 image, which I am also attaching. The script is intentially
not a simple turnkey solution, since you should be somewhat familiar with the
GCE infrastructure before using it. However, feel free to ask questions if
anything is unclear.

Returning back to config.scm, the only other non-obvious pieces deal with the
bootloader setup. On GCE at boot time, our only choice of interface is a serial
console, so the following set that up in case it becomes necessary:


      (bootloader (bootloader-configuration
                    ...
                    (serial-speed 115200)
                    (terminal-outputs '(serial))
                    (terminal-inputs '(serial))))

      (kernel-arguments '("console=ttyS0,115200"))

We set the baud rate to 115200 instead of the default 9600, for two reasons.
One it is essential that grub.cfg get populated with the following:

    serial [options]
    terminal_output serial
    terminal_input serial

and for some reason, bootloader-configuration seems to elide these lines
without serial-speed set to something other than 9600. Secondly, baud 115200
ends up providing a better shell experience anyway.

Finally, the attached config.scm sets a bootloader timeout of 0:

      (bootloader (bootloader-configuration
                    ...
                    (timeout 0)))

Since the vm is completely headless during normal bootup, anything else just
slows down boot times.


Finally, GCE allows community supported images [4]. If there is enough
interest, it might make sense to invest the few cents per month to maintain a
Guix System one. Thoughts?

Hopefully, the above is clear. I am happy to answer any questions.


[0]:https://lists.gnu.org/archive/html/guix-devel/2017-01/msg01815.html
[1]:https://ftp.gnu.org/gnu/guix/guix-system-vm-image-1.0.1.x86_64-linux.xz
[2]:https://cloud.google.com/compute/docs/images/building-custom-os
[3]:https://cloud.google.com/compute/docs/import/import-existing-image
[4]:https://cloud.google.com/compute/docs/images#community_supported_images

config.scm
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gce.sh
Description: Text document

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