Allow an image URL instead of a template reference

[jandubois]

The template.Read() method will guess the architecture based on the image filename and construct a template dynamically.

It also strips generic tags from the image name to generate an instance name candidate.

❯ limactl start --containerd none https://dl-cdn.alpinelinux.org/alpine/v3.21/releases/cloud/nocloud_alpine-3.21.2-aarch64-uefi-cloudinit-r0.qcow2
...

❯ limactl shell alpine-3.21.2-r0 uname -a
Linux lima-alpine-3-21-2-r0 6.12.8-0-virt #1-Alpine SMP PREEMPT_DYNAMIC 2025-01-02 12:14:41 aarch64 Linux

Closes #3322

This code needs to be updated with s390x heuristics once #3319 is merged (or the other way around, depending on which one is merged first).

[jandubois]

This implementation also allows you to use image URLs as base templates:

❯ cat my.yaml
base: https://yum.oracle.com/templates/OracleLinux/OL8/u10/aarch64/OL8U10_aarch64-kvm-cloud-b100.qcow2

❯ limactl tmpl copy --embed my.yaml -
WARN[0000] `base` is experimental

arch: "aarch64"
images:
- location: "https://yum.oracle.com/templates/OracleLinux/OL8/u10/aarch64/OL8U10_aarch64-kvm-cloud-b100.qcow2"
  arch: "aarch64"

❯ limactl start my.yaml
...

❯ limactl shell my grep PRETTY /etc/os-release
PRETTY_NAME="Oracle Linux Server 8.10"

[AkihiroSuda]

MaybefileName.trimPrefix("nocloud_").splitWords[0].toLower() just suffices

e.g.,

• nocloud_alpine-3.21.2-x86_64-uefi-cloudinit-r0.qcow2 -> alpine
• ubuntu-24.10-server-cloudimg-arm64.img -> ubuntu

Arch-Linux-x86_64-cloudimg-20250201.304316.qcow2 may still needs an exceptional rule though, if we want the instance name to be archlinux, not arch

[jandubois]

I kind of like the more descriptive names. You can always use --name ubuntu https//... if you want a really short name or predictable name.

So I would prefer to keep the current logic, unless you really dislike it.

Also don't want to add unit tests if you are going to make me remove it again. 😄

[AkihiroSuda]

@lima-vm/maintainers Thoughts?

[jandubois]

Arch-Linux-x86_64-cloudimg-20250201.304316.qcow2 may still needs an exceptional rule though, if we want the instance name to be archlinux, not arch

I just noticed that I didn't add linux to the list of generic tags. I would want to strip that too, so the default instance name for this image would be arch-20250201.304316.

[jandubois]

I've selected all image names from all our templates and filtered out just the amd64 ones:

find templates -name "*.yaml" -exec yq '.images[].location' {} \; | xargs basename | sed s/nocloud_// | sort -fu | grep -E 'amd|x86'

I've then manually transformed each of them into the instance name produced by the current algorithm:

almalinux-8
almalinux-8-8.10-20240819
almalinux-9
almalinux-9-9.5-20241120
alpine-3.21.2-r0
alpine-lima-3.20.3
arch
arch-20250201.304316
centos-10
centos-10-20250210.0
centos-9
centos-9-20250210.0
debian-11
debian-11-20241202-1949
debian-12
debian-12-20250210-2019
debian-sid
fedora-41-1.4
gentoo
ol8u10-b237
ol9u5-b253
opensuse-leap-15.6
opensuse-tumbleweed
rocky-8
rocky-8-8.10-20240528.0
rocky-9
rocky-9-9.5-20241118.0
ubuntu-20.04
ubuntu-22.04
ubuntu-24.04
ubuntu-24.10

I think the names look reasonable, and I would prefer them to just picking the first word from the string.

[jandubois]

I've added a special rule to translate arch to archlinux and another rule to strip the datestamps, which leaves us with this list of instance names (duplicates pruned):

almalinux-8
almalinux-8-8.10
almalinux-9
almalinux-9-9.5
alpine-3.21.2-r0
alpine-lima-3.20.3
archlinux
centos-10
centos-9
debian-11
debian-12
debian-sid
fedora-41-1.4
gentoo
ol8u10-b237
ol9u5-b253
opensuse-leap-15.6
opensuse-tumbleweed
rocky-8
rocky-8-8.10
rocky-9
rocky-9-9.5
ubuntu-20.04
ubuntu-22.04
ubuntu-24.04
ubuntu-24.10

[jandubois]

Changes:

• Add "linux" and "daily" to list of generic tags
• Change "arch" to "archlinux"
• Strip timestamps from instance names
• Created InstNameFromImageURL function and added unit tests
• Remove blank first line from the generated image template
• Added unit test for image URL expansion into a template

[AkihiroSuda]

Thanks