KEP-4762: Allows setting any FQDN as the pod's hostname #4768

HirazawaUi · 2024-07-18T16:26:53Z

One-line PR description: Allows users to set any FQDN as the hostname of a pod

Issue link: Allows setting any FQDN as the pod's hostname #4762

Other comments:

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

HirazawaUi · 2024-07-21T15:41:33Z

/cc @thockin

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

k8s-triage-robot · 2025-01-19T13:10:09Z

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/lifecycle stale

HirazawaUi · 2025-01-20T00:19:03Z

/remove-lifecycle stale

HirazawaUi · 2025-01-20T01:15:58Z

ping @thockin

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

k8s-triage-robot · 2025-04-20T16:14:41Z

The Kubernetes project currently lacks enough contributors to adequately respond to all PRs.

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/lifecycle stale

thockin

LGTM from API
/approve

keps/prod-readiness/sig-network/4762.yaml

thockin · 2025-06-09T15:42:49Z

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

+| Behavior                                                     | result for `hostname`                                | result for `hostname -f`                             | DNS Record                                           |
+| ------------------------------------------------------------ | ---------------------------------------------------- | ---------------------------------------------------- | ---------------------------------------------------- |
+| hostname: busybox1                                           | busybox1                                             | busybox1                                             | None                                                 |
+| hostname: busybox1<br />subdomain: busybox-subdomain         | busybox1                                             | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local |
+| hostname: busybox1<br />subdomain: busybox-subdomain<br />setHostnameAsFQDN: true | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local |
+| hostnameOverride: www.example.com                           | www.example.com                                      | www.example.com                                      | None                                                 |
+| hostname: busybox1<br />hostnameOverride: www.example.com   | www.example.com                                      | www.example.com                                      | None                                                 |
+| hostname: busybox1<br />hostnameOverride: www.example.com<br />subdomain: busybox-subdomain | www.example.com                                      | www.example.com                                      | busybox1.busybox-subdomain.default.svc.cluster.local |


Suggested change

| Behavior | result for `hostname` | result for `hostname -f` | DNS Record |

| ------------------------------------------------------------ | ---------------------------------------------------- | ---------------------------------------------------- | ---------------------------------------------------- |

| hostname: busybox1 | busybox1 | busybox1 | None |

| hostname: busybox1 subdomain: busybox-subdomain | busybox1 | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local |

| hostname: busybox1 subdomain: busybox-subdomain setHostnameAsFQDN: true | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local |

| hostnameOverride: www.example.com | www.example.com | www.example.com | None |

| hostname: busybox1 hostnameOverride: www.example.com | www.example.com | www.example.com | None |

| hostname: busybox1 hostnameOverride: www.example.com subdomain: busybox-subdomain | www.example.com | www.example.com | busybox1.busybox-subdomain.default.svc.cluster.local |

| # | `.hostname` | `.subdomain` | `.setHostnameAsFQDN` | `.hostnameOverride` | `$(hostname)` | `$(hostname -f)` | DNS (assuming service exists) |

| -- | ----------- | ------------ | -------------------- | ------------------- | ------------------------------ | ------------------------------ | ------------------------------ |

| 0 | | | | | `<podname>` | `<podname>` | |

| 1 | `aa` | | | | `aa` | `aa` | |

| 2 | | `bb` | | | `<podname>` | `<podname>.bb.<ns>.svc.<zone>` | `<podname>.bb.<ns>.svc.<zone>` |

| 3 | `aa` | `bb` | | | `aa` | `aa.bb.<ns>.svc.<zone>` | `aa.bb.<ns>.svc.<zone>` |

| 4 | | | true | | `<podname>` | `<podname>` | |

| 5 | `aa` | | true | | `aa` | `aa` | |

| 6 | | `bb` | true | | `<podname>.bb.<ns>.svc.<zone>` | `<podname>.bb.<ns>.svc.<zone>` | `<podname>.bb.<ns>.svc.<zone>` |

| 7 | `aa` | `bb` | true | | `aa.bb.<ns>.svc.<zone>` | `aa.bb.<ns>.svc.<zone>` | `aa.bb.<ns>.svc.<zone>` |

| 8 | | | | `xx.yy.zz` | `xx.yy.zz` | `xx.yy.zz` | |

| 9 | `aa` | | | `xx.yy.zz` | `xx.yy.zz` | `xx.yy.zz` | |

| 10 | | `bb` | | `xx.yy.zz` | `xx.yy.zz` | `xx.yy.zz` | `<podname>.bb.<ns>.svc.<zone>` |

| 11 | `aa` | `bb` | | `xx.yy.zz` | `xx.yy.zz` | `xx.yy.zz` | `aa.bb.<ns>.svc.<zone>` |

| 12 | | | true | `xx.yy.zz` | INVALID | INVALID | INVALID |

| 13 | `aa` | | true | `xx.yy.zz` | INVALID | INVALID | INVALID |

| 14 | | `bb` | true | `xx.yy.zz` | INVALID | INVALID | INVALID |

| 15 | `aa` | `bb` | true | `xx.yy.zz` | INVALID | INVALID | INVALID |

Thank you very much for providing this table. I had promised to improve it over the weekend, but got caught up with other matters. Anyway, thank you very much.

I didn't want to lose track of it, and I think it should probably go into the k8s docs in some nicer form :)

@lmktfy

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

SergeyKanzhelev

lgtm, except I suggest this be tested with the Conformance tests. Maybe add it also to graduation criteria

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

Co-authored-by: Tim Hockin <thockin@google.com>

thockin · 2025-06-10T16:07:38Z

Thanks!

/lgtm
/approve

thockin · 2025-06-11T15:26:07Z

For viz: Joe is OOO this week - can @deads2k or @soltysh take this one?

soltysh

Left several comments.

keps/prod-readiness/sig-network/4762.yaml

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/kep.yaml

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

soltysh · 2025-06-13T11:46:11Z

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

+
+###### Were upgrade and rollback tested? Was the upgrade->downgrade->upgrade path tested?
+
+N/A


This is fine for alpha, but you'll need to perform manual tests for beta promotion.

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/README.md

keps/sig-network/4762-allow-arbitrary-fqdn-as-pod-hostname/kep.yaml

HirazawaUi · 2025-06-13T14:43:26Z

@soltysh Thank you so much for taking the time with this KEP! I've addressed all the PRR comments, could you please take another look?

soltysh

/approve
the PRR

k8s-ci-robot · 2025-06-17T11:50:23Z

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: HirazawaUi, soltysh, thockin

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

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soltysh · 2025-06-17T11:51:11Z

lgtm, except I suggest this be tested with the Conformance tests. Maybe add it also to graduation criteria

Thanks!

/lgtm /approve

Since this was already tagged by Sergey and Tim, I'll go ahead and re-apply it

/lgtm
/label tide/merge-method-squash

HirazawaUi · 2025-06-17T14:30:50Z

Great to see this PR merged! Truly appreciate everyone's patient reviews and assistance.

k8s-ci-robot added the cncf-cla: yes Indicates the PR's author has signed the CNCF CLA. label Jul 18, 2024

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HirazawaUi commented Jul 18, 2024

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Allows setting any FQDN as the pod's hostname #4762

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Override pod hostname

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Updating the configuration table

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Co-authored-by: Tim Hockin <thockin@google.com>

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-| Behavior                                                     | result for `hostname`                                | result for `hostname -f`                             | DNS Record                                           |
-| ------------------------------------------------------------ | ---------------------------------------------------- | ---------------------------------------------------- | ---------------------------------------------------- |
-| hostname: busybox1                                           | busybox1                                             | busybox1                                             | None                                                 |
-| hostname: busybox1<br />subdomain: busybox-subdomain         | busybox1                                             | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local |
-| hostname: busybox1<br />subdomain: busybox-subdomain<br />setHostnameAsFQDN: true | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local | busybox1.busybox-subdomain.default.svc.cluster.local |
-| hostnameOverride: www.example.com                           | www.example.com                                      | www.example.com                                      | None                                                 |
-| hostname: busybox1<br />hostnameOverride: www.example.com   | www.example.com                                      | www.example.com                                      | None                                                 |
-| hostname: busybox1<br />hostnameOverride: www.example.com<br />subdomain: busybox-subdomain | www.example.com                                      | www.example.com                                      | busybox1.busybox-subdomain.default.svc.cluster.local |
+|  # | `.hostname` | `.subdomain` | `.setHostnameAsFQDN` | `.hostnameOverride` | `$(hostname)`                  | `$(hostname -f)`               | DNS (assuming service exists)  |
+| -- | ----------- | ------------ | -------------------- | ------------------- | ------------------------------ | ------------------------------ | ------------------------------ |
+|  0 |             |              |                      |                     | `<podname>`                    | `<podname>`                    |                                |
+|  1 | `aa`        |              |                      |                     | `aa`                           | `aa`                           |                                |
+|  2 |             | `bb`         |                      |                     | `<podname>`                    | `<podname>.bb.<ns>.svc.<zone>` | `<podname>.bb.<ns>.svc.<zone>` |
+|  3 | `aa`        | `bb`         |                      |                     | `aa`                           | `aa.bb.<ns>.svc.<zone>`        | `aa.bb.<ns>.svc.<zone>`        |
+|  4 |             |              | true                 |                     | `<podname>`                    | `<podname>`                    |                                |
+|  5 | `aa`        |              | true                 |                     | `aa`                           | `aa`                           |                                |
+|  6 |             | `bb`         | true                 |                     | `<podname>.bb.<ns>.svc.<zone>` | `<podname>.bb.<ns>.svc.<zone>` | `<podname>.bb.<ns>.svc.<zone>` |
+|  7 | `aa`        | `bb`         | true                 |                     | `aa.bb.<ns>.svc.<zone>`        | `aa.bb.<ns>.svc.<zone>`        | `aa.bb.<ns>.svc.<zone>`        |
+|  8 |             |              |                      | `xx.yy.zz`          | `xx.yy.zz`                     | `xx.yy.zz`                     |                                |
+|  9 | `aa`        |              |                      | `xx.yy.zz`          | `xx.yy.zz`                     | `xx.yy.zz`                     |                                |
+| 10 |             | `bb`         |                      | `xx.yy.zz`          | `xx.yy.zz`                     | `xx.yy.zz`                     | `<podname>.bb.<ns>.svc.<zone>` |
+| 11 | `aa`        | `bb`         |                      | `xx.yy.zz`          | `xx.yy.zz`                     | `xx.yy.zz`                     | `aa.bb.<ns>.svc.<zone>`        |
+| 12 |             |              | true                 | `xx.yy.zz`          | INVALID                        | INVALID                        | INVALID                        |
+| 13 | `aa`        |              | true                 | `xx.yy.zz`          | INVALID                        | INVALID                        | INVALID                        |
+| 14 |             | `bb`         | true                 | `xx.yy.zz`          | INVALID                        | INVALID                        | INVALID                        |
+| 15 | `aa`        | `bb`         | true                 | `xx.yy.zz`          | INVALID                        | INVALID                        | INVALID                        |


		###### Were upgrade and rollback tested? Was the upgrade->downgrade->upgrade path tested?

		N/A

KEP-4762: Allows setting any FQDN as the pod's hostname #4768

KEP-4762: Allows setting any FQDN as the pod's hostname #4768

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HirazawaUi commented Jul 18, 2024

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