exec: use qemu emulator automatically #1516
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tiborvass
reviewed
Jun 3, 2020
Dockerfile
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| @@ -101,6 +101,8 @@ RUN --mount=target=. --mount=target=/root/.cache,type=cache \ | |||
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| FROM scratch AS binaries-linux-helper | |||
| COPY --from=runc /usr/bin/runc /buildkit-runc | |||
| # built from https://github.com/tonistiigi/binfmt/tree/85394e2a1bf0ac9e6c291945e869322bea969445 | |||
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tiborvass
reviewed
Jun 3, 2020
tiborvass
reviewed
Jun 3, 2020
| @@ -708,6 +708,17 @@ func (e *execOp) Exec(ctx context.Context, inputs []solver.Result) ([]solver.Res | |||
| return nil, err | |||
| } | |||
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| emu, err := getEmulator(e.platform, e.cm.IdentityMapping()) | |||
| if err == nil && emu != nil { | |||
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Log error instead of silencing it
AkihiroSuda
reviewed
Jun 4, 2020
solver/llbsolver/ops/exec_binfmt.go
Outdated
| return []mount.Mount{{ | ||
| Type: "bind", | ||
| Source: filepath.Join(tmpdir, qemuMountName), | ||
| Options: []string{"ro", "rbind"}, |
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Setting ro and rbind together isn't useful because it does not make the mountpoint recursively read-only.
Signed-off-by: Tonis Tiigi <[email protected]>
AkihiroSuda
approved these changes
Jun 8, 2020
tiborvass
approved these changes
Jun 8, 2020
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fixes #1513
This allows emulation for multi-arch in 6 most popular architectures without kernel being configured with binfmt_misc. If kernel is configured binfmt_misc is used instead.
Currently, all the qemu binaries are included with the image. After gzip for x86 this means ~7MB size increase. https://github.com/tonistiigi/binfmt/releases/tag/test0 That should be ok for most cases. I'm not sure if it is ok for Moby though so maybe we should also allow qemu to be pulled from the image during build. There may be licensing issues as well for shipping these qemu binaries with dockerd.
Another possible optimization would be to avoid cloning emulator binary for each exec. Some cache could be introduced.
The approach of switching entrypoint seems to work on my test builds but lmk if you can spot some possible issues with this.
Signed-off-by: Tonis Tiigi [email protected]