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docs: clarify a caveat with COPY --link and overwriting directory permissions #6778

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tonistiigi merged 1 commit into from
May 29, 2026
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docs: clarify a caveat with COPY --link and overwriting directory permissions #6778

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7 changes: 7 additions & 0 deletions frontend/dockerfile/docs/reference.md
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Expand Up @@ -1967,6 +1967,13 @@ path, using `--link` is always recommended. The performance of `--link` is
equivalent or better than the default behavior and, it creates much better
conditions for cache reuse.

When copying a path into a subdirectory, `--link` will always copy from the
root of the filesystem. When copying a directory, the existing mode is
overridden with the new mode from the copied path. If you need a specific mode
for a directory, such as the more permissive `/tmp` directory, you may need to
either avoid using `--link`, unroll the copy into its base components, or use
`--chmod` to ensure the overwriting directory contains the same permissions.

### COPY --parents

```dockerfile
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