✨ Init Ubuntu 26 - New release Resolute by Whisper40 · Pull Request #1987 · kubernetes-sigs/image-builder

Whisper40 · 2026-04-23T13:03:14Z

Change description

The goal of this PR is to initiate the work for Ubuntu 26.

Is this change including a new Provider or a new OS? (y/n) yes
If yes, has the Provider/OS matrix been updated in the readme? (y/n) yes
If adding a new provider, are you a representative of that provider? (y/n) no

Related issues

Fixes #

Additional context

k8s-ci-robot · 2026-04-23T13:03:22Z

[APPROVALNOTIFIER] This PR is NOT APPROVED

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k8s-ci-robot · 2026-04-23T13:03:25Z

Hi @Whisper40. Thanks for your PR.

I'm waiting for a kubernetes-sigs member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work.

Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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Whisper40 · 2026-04-23T13:12:53Z

i'm waiting the "ok-to-test" to start debugging :)

AndiDog · 2026-04-24T07:54:25Z

/ok-to-test

Whisper40 · 2026-04-24T09:01:35Z

/retest

Whisper40 · 2026-04-24T11:47:15Z

/retest

Whisper40 · 2026-04-24T11:50:25Z

/retest

Whisper40 · 2026-04-24T12:20:19Z

/retest

Whisper40 · 2026-04-24T12:41:37Z

/retest

Whisper40 · 2026-04-24T13:46:10Z

Azure pull failing due to Ubuntu 26.04 not available on Azure..
https://az-vm-image.info/?cmd=--offer+ubuntu

Whisper40 · 2026-04-24T14:25:04Z

/retest

Whisper40 · 2026-04-24T14:45:04Z

/retest

Whisper40 · 2026-04-24T15:03:20Z

@AndiDog Hi, the CI is actually not failing due to Ubuntu26 but Photon5

almalinux-9: SUCCESS
ubuntu-2404: SUCCESS
ubuntu-2604: SUCCESS
rockylinux-9: SUCCESS
flatcar: SUCCESS
photon-5: FAILED. See logs in the artifacts folder.
ubuntu-2204: SUCCESS

For Azure failure :
Azure pull failing due to Ubuntu 26.04 not available on Azure..
https://az-vm-image.info/?cmd=--offer+ubuntu

AndiDog

Apart from inline comments, docs/book/src/capi/providers/maas.md says

The image will be located in images/capi/output/BUILD_NAME+kube-KUBERNETES_VERSION. Replace xxxx with 2204 or 2404, depending on the Ubuntu version.

From the PR diff, I guess 2604 should also be available. Let's remove the mention of the very old 2204 in that file as well.

There should be official builds since April 23rd (yesterday), let's try removing the beta parts.

This is based on a deep AI review, btw. I didn't find the time yet to check this out myself.

Would you mind telling us which images you tried building yourself, and ran them successfully on a Kubernetes cluster? If any... no worries if that didn't happen yet 😉.

AndiDog · 2026-04-24T20:37:45Z

@@ -0,0 +1,6 @@
+{
+  "build_name": "ubuntu-2604",
+  "os": "2284",


This is copy-pasted. Here's the actual ID (for the record how to find this out, since it's hard to google):

$ vultr os list Error reading in config file (/Users/asommer/.vultr-cli.yaml) : open /Users/asommer/.vultr-cli.yaml: no such file or directoryID NAME ARCH FAMILY 159 Custom x64 iso 164 Snapshot x64 snapshot 180 Backup x64 backup 186 Application x64 application 240 Windows 2016 Standard x64 x64 windows 371 Windows 2019 Standard x64 x64 windows 391 Fedora CoreOS Stable x64 fedora-coreos 424 Fedora CoreOS Next x64 fedora-coreos 425 Fedora CoreOS Testing x64 fedora-coreos 447 FreeBSD 13 x64 x64 freebsd 448 Rocky Linux x64 x64 rockylinux 452 AlmaLinux x64 x64 almalinux 477 Debian 11 x64 (bullseye) x64 debian 501 Windows 2022 Standard x64 x64 windows 521 Windows Core 2022 Standard x64 x64 windows 522 Windows Core 2016 Standard x64 x64 windows 523 Windows Core 2019 Standard x64 x64 windows 535 Arch Linux x64 x64 archlinux 542 CentOS 9 Stream x64 x64 centos 1743 Ubuntu 22.04 LTS x64 x64 ubuntu 1761 Windows Core 2019 Datacenter x64 x64 windows 1762 Windows Core 2022 Datacenter x64 x64 windows 1764 Windows 2019 Datacenter x64 x64 windows 1765 Windows 2022 Datacenter x64 x64 windows 1868 AlmaLinux 9 x64 x64 almalinux 1869 Rocky Linux 9 x64 x64 rockylinux 2075 Flatcar Container Linux LTS x64 x64 flatcar 2076 Alpine Linux x64 x64 alpinelinux 2077 Flatcar Container Linux Stable x64 x64 flatcar 2078 Flatcar Container Linux Beta x64 x64 flatcar 2079 Flatcar Container Linux Alpha x64 x64 flatcar 2136 Debian 12 x64 (bookworm) x64 debian 2157 openSUSE Leap 15 x64 x64 opensuse 2212 FreeBSD 14 x64 x64 freebsd 2284 Ubuntu 24.04 LTS x64 x64 ubuntu 2467 CentOS 10 Stream x64 x64 centos 2514 Windows 2025 Standard x64 x64 windows 2515 Windows 2025 Datacenter x64 x64 windows 2516 Windows Core 2025 Standard x64 x64 windows 2517 Windows Core 2025 Datacenter x64 x64 windows 2572 Fedora 42 x64 x64 fedora 2573 OpenBSD 7.7 x64 x64 openbsd 2593 AlmaLinux 10 x64 x64 almalinux 2594 Rocky Linux 10 x64 x64 rockylinux 2625 Debian 13 x64 (trixie) x64 debian 2656 openSUSE Leap 16 x64 x64 opensuse 2657 Ubuntu 25.10 x64 x64 ubuntu 2658 Fedora 43 x64 x64 fedora 2659 OpenBSD 7.8 x64 x64 openbsd 2720 FreeBSD 15 x64 x64 freebsd 2752 Fedora 44 x64 x64 fedora 2760 Ubuntu 26.04 LTS x64 x64 ubuntu ====================================== TOTAL NEXT PAGE PREV PAGE 52 --- ---

Everything related to Ubuntu 22 could be removed in another PR, once we release Ubuntu 26

It seems that we have time before deleting the 2204 image !
https://endoflife.date/ubuntu

Whisper40 · 2026-04-27T09:42:10Z

@AndiDog Check this link, Ubuntu 26 is not available for Azure. The beta part has been removed for few days

Whisper40 · 2026-04-27T09:42:15Z

/retest

Whisper40 · 2026-04-27T09:49:57Z

/retest

Whisper40 · 2026-04-27T11:50:20Z

/retest

Whisper40 · 2026-04-27T12:22:34Z

/retest

Whisper40 · 2026-04-27T13:06:30Z

/retest

Whisper40 · 2026-04-27T13:11:24Z

/retest

Whisper40 · 2026-04-27T13:13:06Z

@AndiDog The CVM image for Ubuntu 26 is not yet available on Azure, it's why it is failing actually.

Whisper40 · 2026-04-27T15:32:17Z

/retest

Whisper40 · 2026-04-27T20:13:57Z

/retest

Whisper40 · 2026-04-27T20:14:58Z

OVA 2604 seems OK.
What's your decision about azure build ? (disable building cvm ubuntu 26 until they publish it ?)

Whisper40 · 2026-04-27T20:39:35Z

/retest

AndiDog · 2026-04-28T12:24:35Z

@mboersma what can we do about Azure not having Ubuntu 26.04 yet? Any idea when it will be made available?

Whisper40 · 2026-04-28T12:38:47Z

/retest

Whisper40 · 2026-04-28T12:40:32Z

/retest

Whisper40 · 2026-04-29T07:30:30Z

/retest

vasartori · 2026-04-29T13:59:50Z

@Whisper40 I was looking at the PR with focus on MaaS.
The initial problem I got was the memory size of the QEMU VM. 2G seems to be too slow for Ubuntu 26. For my tests, I have increased the size to 4G and the install works as well.
Probably, this problem also occurs in QEMU builds.

I'm testing the build then, I'll launch a cluster to see what happens. I'll post the results later.

vasartori · 2026-04-29T14:31:31Z

@Whisper40 I was looking at the PR with focus on MaaS. The initial problem I got was the memory size of the QEMU VM. 2G seems to be too slow for Ubuntu 26. For my tests, I have increased the size to 4G and the install works as well. Probably, this problem also occurs in QEMU builds.

I'm testing the build then, I'll launch a cluster to see what happens. I'll post the results later.

Just changing the memory size, everything works as well using MaaS 3.7.2.

Whisper40 · 2026-04-30T07:45:39Z

@mboersma Hi, any news about the azure image for Ubuntu 26.04 CVM ? Should we disable the build until it is available ?

- Update Makefile, azure_targets.sh, init-sig.sh with ubuntu-2604 targets - Remove Azure CVM target - Replace deprecated apt_key with signed-by keyring approach (all roles) - Map Azure CLI codename resolute->noble (no MS repo for 26.04 yet) - Set QEMU memory to 4GB for Ubuntu 26.04 - Update README.md and all provider docs

k8s-ci-robot · 2026-04-30T08:55:26Z

@Whisper40: The following tests failed, say /retest to rerun all failed tests or /retest-required to rerun all mandatory failed tests:

Test name	Commit	Details	Required	Rerun command
pull-ova-all	`f7e259c`	link	false	`/test pull-ova-all`
pull-azure-sigs	`f7e259c`	link	false	`/test pull-azure-sigs`

Full PR test history. Your PR dashboard. Please help us cut down on flakes by linking to an open issue when you hit one in your PR.

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hiento09 · 2026-05-03T18:05:08Z

Hi @Whisper40,

Thanks for taking on the Ubuntu 26.04 work — really appreciate it!

I tested your branch with a Kamaji-managed CAPI cluster on OpenStack (worker-only, kubeadm bootstrap). Build succeeds and VMs boot fine, but every node fails to join with:

[preflight] Some fatal errors occurred:
[ERROR FileContent--proc-sys-net-ipv4-ip_forward]: /proc/sys/net/ipv4/ip_forward contents are not set to 1

Root cause: the node role writes kernel params to /etc/sysctl.conf (default sysctl_conf_file for Debian-family). Ubuntu 26.04 ships systemd 259, which no longer loads /etc/sysctl.conf at boot — only /etc/sysctl.d/*.conf / /run/sysctl.d/*.conf / /usr/lib/sysctl.d/*.conf. So the file gets written during build but the params never apply on first boot, and kubeadm preflight rejects the join.

I patched it locally to switch the default to /etc/sysctl.d/99-sysctl.conf for Ubuntu ≥ 26, leaving older releases on the legacy path:

# images/capi/ansible/roles/node/defaults/main.yml
sysctl_conf_file: >-
  {{ '/etc/sysctl.d/99-sysctl.conf' if ansible_facts['os_family'] in ['Common Base Linux Mariner', 'Flatcar', 'Microsoft Azure Linux', 'VMware Photon OS']
    or (ansible_facts['distribution'] == 'Ubuntu' and (ansible_facts['distribution_major_version'] | int) >= 26)
    else '/etc/sysctl.conf' }}

Rebuilt with this change and worker nodes join cleanly — net.ipv4.ip_forward=1 is set at boot, kubeadm preflight passes, kubelet registers, node goes Ready. Same image keeps working on Ubuntu 24.04 (no behaviour change there).

Just flagging so you can fold it into this PR — would be great to have 26.04 usable out of the box. Thanks again!

k8s-ci-robot · 2026-05-06T23:48:16Z

PR needs rebase.

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k8s-ci-robot requested review from CecileRobertMichon and chrischdi April 23, 2026 13:03

k8s-ci-robot added the needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. label Apr 23, 2026

k8s-ci-robot added size/XXL Denotes a PR that changes 1000+ lines, ignoring generated files. cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. labels Apr 23, 2026

Whisper40 marked this pull request as draft April 23, 2026 13:07

k8s-ci-robot added the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Apr 23, 2026

k8s-ci-robot added ok-to-test Indicates a non-member PR verified by an org member that is safe to test. and removed needs-ok-to-test Indicates a PR that requires an org member to verify it is safe to test. labels Apr 24, 2026

AndiDog reviewed Apr 24, 2026

View reviewed changes

joshfrench mentioned this pull request Apr 27, 2026

Add support for arm64-based AMIs #1988

Merged

Whisper40 marked this pull request as ready for review April 27, 2026 20:21

k8s-ci-robot removed the do-not-merge/work-in-progress Indicates that a PR should not merge because it is a work in progress. label Apr 27, 2026

k8s-ci-robot requested a review from AndiDog April 27, 2026 20:21

Whisper40 force-pushed the try-ubuntu26 branch from aaa2a85 to f7e259c Compare April 30, 2026 08:06

k8s-ci-robot added the needs-rebase Indicates a PR cannot be merged because it has merge conflicts with HEAD. label May 6, 2026

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