daemon: raise default minimum API version to v1.44

[thaJeztah]

• relates to 96b29f5 client: remove support for negotiating API version < v1.44 (docker 25.0) #51119
• similar to 08e4e88 daemon: raise default minimum API version to v1.24 #46887

The daemon currently provides support for API versions all the way back to v1.24, which is the version of the API that shipped with docker 1.12.0 (released in 2016).

Such old versions of the client are rare, and supporting older API versions has accumulated significant amounts of code to remain backward-compatible (which is largely untested, and a "best-effort" at most).

This patch updates the minimum API version to v1.44, matching the minimum version of the client, and matching the API version of docker v25.0, which is the oldest supported version (through Mirantis MCR).

The intent is to start deprecating older API versions when daemons implementing them reach EOL. This patch does not yet remove backward-compatibility code for older API versions, and the DOCKER_MIN_API_VERSION environment variable allows overriding the minimum version (to allow restoring the behavior from before this patch), however, API versions below v1.44 should be considered "best effort", and we may remove compatibility code to provide "degraded" support.

With this patch the daemon defaults to API v1.44 as minimum:

docker version
Client:
 Version:           28.5.0
 API version:       1.51
 Go version:        go1.24.7
 Git commit:        887030f
 Built:             Thu Oct  2 14:54:39 2025
 OS/Arch:           linux/arm64
 Context:           default

Server:
 Engine:
  Version:          dev
  API version:      1.52 (minimum version 1.44)
....

Trying to use an older version of the API produces an error:

DOCKER_API_VERSION=1.43 docker version
Client:
 Version:           28.5.0
 API version:       1.43 (downgraded from 1.51)
 Go version:        go1.24.7
 Git commit:        887030f
 Built:             Thu Oct  2 14:54:39 2025
 OS/Arch:           linux/arm64
 Context:           default
Error response from daemon: client version 1.43 is too old. Minimum supported API version is 1.44, please upgrade your client to a newer version

To restore the previous minimum, users can start the daemon with the DOCKER_MIN_API_VERSION environment variable set:

DOCKER_MIN_API_VERSION=1.24 dockerd

API 1.24 is the oldest supported API version;

docker version
Client:
 Version:           28.5.0
 API version:       1.24 (downgraded from 1.51)
 Go version:        go1.24.7
 Git commit:        887030f
 Built:             Thu Oct  2 14:54:39 2025
 OS/Arch:           linux/arm64
 Context:           default

Server:
 Engine:
  Version:          dev
  API version:      1.52 (minimum version 1.24)
....

When using the DOCKER_MIN_API_VERSION with a version of the API that is not supported, an error is produced when starting the daemon;

DOCKER_MIN_API_VERSION=1.23 dockerd --validate
invalid DOCKER_MIN_API_VERSION: minimum supported API version is 1.24: 1.23

DOCKER_MIN_API_VERSION=1.99 dockerd --validate
invalid DOCKER_MIN_API_VERSION: maximum supported API version is 1.52: 1.99

Specifying a malformed API version also produces the same error;

DOCKER_MIN_API_VERSION=hello dockerd --validate
invalid DOCKER_MIN_API_VERSION: minimum supported API version is 1.24: hello

- What I did

- How I did it

- How to verify it

- Human readable description for the release notes

daemon: raise default minimum API version to v1.44

- A picture of a cute animal (not mandatory but encouraged)

[akerouanton]

LGTM. I think we should mention in the release notes when we're planning to drop support for these older API versions such that affected users can anticipate.

[austinvazquez]

I think this is reasonable expectation of the API support.

[thompson-shaun]

Let's make a docs issue to support this @vvoland @austinvazquez ❤️

[thaJeztah]

Also to look for mainstream projects that need an update (good catch, @vvoland); we can contribute a patch for traefik at least; possibly could use version-negotiation as weell, but at least update to v1.44; I think I also saw a separate Swarm version const, so also need to look at that;
https://github.com/traefik/traefik/blob/05de0670ea9fe4c66e6abeb8868acfcff3b9b4b7/pkg/provider/docker/pdocker.go#L24-L25
https://github.com/traefik/traefik/blob/05de0670ea9fe4c66e6abeb8868acfcff3b9b4b7/pkg/provider/docker/shared.go#L111-L129

☝️ this should give a starting-point; https://grep.app/search?f.lang=Go&q=client.WithVersion%28

[thaJeztah]

I'll bring this one in; we can have follow-ups where needed 👍