Don't panic if docker version cannot be parsed

[davidgraeff]

I'm using podman instead of Docker (podman has a docker cli interface).
But podman, because it works daemonless, correctly reports no "Server API Version":

Version:            1.5.1
RemoteAPI Version:  1
Go Version:         go1.12.7
OS/Arch:            linux/amd64

A less intrusive version check that just warns would work as well, wouldn't it?

See
https://github.com/rust-embedded/cross/blob/e1470782db43fc737cf9b7f14748331228b8229d/src/docker.rs#L26

Thanks

[reitermarkus]

Can you submit a PR?

[davidgraeff]

Sure

[oblitum]

Would be nice to have official/direct support for podman, it's the simplest solution for running containers rootless, daemonless and safely (without being part of high privileged user groups). I suppose that to use it now one has to provide a docker command that redirects to podman, but still not working due to this issue.

[davidgraeff]

It's not that easy unfortunately. That's why I haven't submitted a patch yet.
Try it out on your machine with this wrapper script:

#!/bin/sh
if [ "$1" == "version" ] && [ "$2" == "--format={{.Server.APIVersion}}" ]; then
echo "100.0"
else
echo "Executing $@"
/usr/bin/podman "$@"
fi

On my fedora system SELinux restricts the container to a degree that nothing works. Disabling SELinux fails with a user-id mapping. The docker daemon does work different than podman in this situation.

[oblitum]

It works on ArchLinux, but needs some fixes. First, your wrapper worked for the image to be pulled, but then what cross executes afterwards cause errors:

❯ cross build --release --locked --target armv7-unknown-linux-gnueabihf
Executing run --userns host --rm --user 1000:1000 -e XARGO_HOME=/xargo -e CARGO_HOME=/cargo -e CARGO_TARGET_DIR=/target -e USER=francisco -e CROSS_RUNNER= -v /home/francisco/.xargo:/xargo:Z -v /home/francisco/.cargo:/cargo:Z -v /cargo/bin -v /home/francisco/Projects/samples/rust:/project:Z,ro -v /home/francisco/.rustup/toolchains/stable-x86_64-unknown-linux-gnu:/rust:Z,ro -v /home/francisco/Projects/samples/rust/target:/target:Z -w /project -i -t rustembedded/cross:armv7-unknown-linux-gnueabihf-0.1.16 sh -c PATH=$PATH:/rust/bin "cargo" "build" "--release" "--locked" "--target" "armv7-unknown-linux-gnueabihf"
Trying to pull docker.io/rustembedded/cross:armv7-unknown-linux-gnueabihf-0.1.16...
Getting image source signatures
Copying blob 515c9bb51536 done
Copying blob e1eabe0537eb done
Copying blob a7344f52cb74 done
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Copying config 3b6c20b612 done
Writing manifest to image destination
Storing signatures
Error: error checking path "/cargo/bin": stat /cargo/bin: no such file or directory

So I executed the command manually with a few edits and the project built:

❯ podman run --userns host --rm -e XARGO_HOME=/xargo -e CARGO_HOME=/cargo -e CARGO_TARGET_DIR=/target -e USER=francisco -e CROSS_RUNNER= -v /home/francisco/.xargo:/xargo:Z -v /home/francisco/.cargo:/cargo:Z -v /home/francisco/Projects/samples/rust:/project:Z -v /home/francisco/.rustup/toolchains/stable-x86_64-unknown-linux-gnu:/rust:Z,ro -v /home/francisco/Projects/samples/rust/target:/target:Z -w /project -i -t rustembedded/cross:armv7-unknown-linux-gnueabihf-0.1.16 sh -c 'PATH=$PATH:/rust/bin cargo build --release --target armv7-unknown-linux-gnueabihf'
   Compiling sample v0.1.0 (/project)
    Finished release [optimized] target(s) in 0.37s

[oblitum]

This is my subgid/subuid setup for rootless podman:

❯ cat /etc/subgid /etc/subuid /proc/self/uid_map
francisco:100000:65536
francisco:100000:65536
         0          0 4294967295

❯ podman unshare cat /proc/self/uid_map
         0       1000          1
         1     100000      65536

[reitermarkus]

I think we could just bump the requirement and assume that Docker supports the --userns flag since the next release will be a breaking change anyways.

[reitermarkus]

Fixed by #344.