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Merge pull request #1211 from sudo-bmitch/pr-cross-layer-hardlink

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Hard link limitations in union filesystems
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Brandon Mitchell 2024-12-05 15:52:37 -05:00 committed by GitHub
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@ -69,6 +69,8 @@ Where supported, MUST include file attributes for Additions and Modifications in
- Non-directory files are considered "hardlinked" when their link count is greater than 1.
- Hardlinked files are on a same device (i.e. comparing Major:Minor pair) and have the same inode.
- The corresponding files that share the link with the > 1 linkcount may be outside the directory that the changeset is being produced from, in which case the `linkname` is not recorded in the changeset.
- Union filesystem implementations may have limited or no support for hardlinks, particularly when a change is made to a hardlinked file or a hardlink is created to a file in a lower filesystem. (See the [overlay specification](https://docs.kernel.org/filesystems/overlayfs.html#index) for more details.)
- Extracting a layer with hardlink references to files outside of the layer may fail.
- Hardlinks are stored in a tar archive with type of a `1` char, per the [GNU Basic Tar Format][gnu-tar-standard] and [libarchive tar(5)][libarchive-tar].
- While approaches to deriving new or changed hardlinks may vary, a possible approach is: