Docker packaging changes in Container Linux Alpha v1451.0.0

[Euan Kemp]

Hello CoreOS Users.

We wanted to give a heads-up on some changes to how we’re running the
docker daemon on Container Linux. These changes are being included in
Container Linux Alpha 1451.0.0, planned for release on June 22nd.

Starting in version 1451.0.0, we’re shipping the docker daemon as a
torcx[1] package. This change by itself doesn’t provide any new
functionality, but it lays the groundwork for allowing a choice of
multiple docker versions in the future (for reasons discussed here[2]).

For normal usage of docker, this change shouldn’t affect you. This
includes all configurations and usage mentioned in our documentation.
That said, there are a couple small changes which could impact some users.

1. The `docker`, `containerd`, and `runc` binaries in `/usr/bin` will be
wrapper scripts.

This means that bind mounting `/usr/bin/docker` into a container might
will not work. This was generally already fragile. If you do need to run
the docker CLI in a container, we recommend including it in the
container directly.

2. The `docker.socket` and `docker.service` will be transient units in /run.

As a result, referencing `/usr/lib/systemd/system/docker.service`
directly, such as using `cat` to view it, will no longer work. The
recommended way of viewing and amending docker’s units (via e.g.
`systemctl cat docker.service` and `systemctl edit docker.service`) will
continue to work, and any overrides, masks, or drop-ins associated with
them will also work.


If you have any questions about these changes, please let us know.

Best,
The Container Linux Team


[1]: https://github.com/coreos/torcx and
https://groups.google.com/d/topic/coreos-dev/_ZUbVD6FkmY/discussion
[2]: https://github.com/coreos/bugs/issues/1930