69 lines
1.8 KiB
Markdown
69 lines
1.8 KiB
Markdown
Undocker
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--------
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Converts a Docker image (a bunch of layers) to a flattened "rootfs" tarball.
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Why?
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----
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Docker images became a popular way to distribute applications with their
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dependencies. However, Docker itself is not the best runtime environment. At
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least not for everyone.
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Undocker bridges the gap between application images (in docker image format)
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and container runtimes: now you can run a Docker image with old-fashioned
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tools: lxc, systemd-nspawn or systemd itself.
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Usage -- extract docker image
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-----------------------------
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Download `nginx` docker image from docker hub and convert it to a rootfs:
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```
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skopeo copy docker://docker.io/busybox:latest docker-archive:busybox.tar
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undocker rootfs busybox.tar - | tar -xv
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```
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Almost the same can be done with a combination of `docker pull` and `docker
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save`.
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Usage -- systemd-nspawn example
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-------------------------------
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Start with systemd-nspawn:
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```
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systemd-nspawn -D $PWD busybox httpd -vfp 8080
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```
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Usage -- plain old systemd
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--------------------------
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```
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systemd-run \
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--wait --pty --collect --service-type=exec \
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-p PrivateUsers=true \
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-p DynamicUser=yes \
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-p ProtectProc=invisible \
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-p RootDirectory=$PWD \
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-- busybox httpd -vfp 8080
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```
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Good things like `PrivateUsers`, `DynamicUser`, `ProtectProc` and other
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[systemd protections][1] are available, just like to any systemd unit.
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Notes & gotchas
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---------------
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`unocker` does not magically enable you to run containers from the internet. In
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fact, many will need significant tuning or not work at all. Thus you will still
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need to understand what are you running.
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Contributions
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-------------
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I will accept pull request for code (including tests) and documentation. I am
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unlikely to react to issue reports without a patch.
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[1]: https://www.freedesktop.org/software/systemd/man/systemd.exec.html
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