integration tests fail to setup overlay within container launch #10
Description
During the impl of #9 I ran into issues trying to create a overlay mount from withing another container, which is part of the unit test harness.
This https://github.com/paritytech/sccache/blob/bernhard-podman/src/bin/sccache-dist/build.rs#L273-L307 piece of code errors out with the following error:
(shortened uuids to d9629, added newlines for readbility)
WARN 2020-11-17T09:31:07Z: sccache::dist::http::server: Res 2 error: run build failed,
caused by: Compilation execution failed,
caused by: Failed to mount overlay FS:
overlayfs "/sccache-bits/build-dir/toolchains/d9629",
upperdir="/sccache-bits/build-dir/builds/d9629-1/upper",
workdir="/sccache-bits/build-dir/builds/d9629-1/work" -> "/sccache-bits/build-dir/builds/d9629-1/target":
Operation not permitted (os error 1) (
"/sccache-bits/build-dir/toolchains/d9629": exists,
upperdir: exists,
workdir: exists,
same-fs,
target: exists,
mapped-root)
To reproduce:
cargo t --features dist-tests test_dist_basic -- --nocapture
in branch bernhard-podman.
Context
The outer container is a rootless podman container.
podman has configurable backends, overlay, vfs, btrfs - the first and last were attempted without any effect.
Adding --privileged or --add-cap CAP_SYS_ADMIN were also attempted for either backend without effect.
Relevant code: https://github.com/paritytech/sccache/blob/bernhard-podman/tests/harness/mod.rs#L354-L387