Using Mercurial on the Andrew File System (AFS)

While AFS provides a POSIX-like interface that is suitable for usage with Mercurial, there are a few details that may surprise casual users.

1. Hardlinks

Because AFS treats every subdirectory as a new filesystem, it is only possible to hardlink between files that exist in the same directory. This prevents the clone command from creating hardlinks, though it should automatically fall back to copying the data.

2. Mercurial and AFS ACLs

In order to use Mercurial with a working directory on an AFS filesystem, the working directory and all directories under it (including the repository, .hg) are accessible by the user. This means that for read-only operations like status, these directories must have at least rl in their ACLs. For operations that change history or lock the repository, at least rliw must be in the ACL list for the working directory and rliwd in the ACL list for the repository (to delete lock files).

To perform read-only operations on a remote repository stored in AFS, l must be in the ACL lists for the parent directory of the repository and rl in the ACL list for the repository itself. Writing to a remote repository requires the same ACLs as when writing to a repository whose working directory is in AFS.

To be confirmed: Mercurial uses its own locking mechanism and doesn't use AFS locks and thus doesn't need the k permission.

3. Interactions with Extensions

It is known that some extensions interact poorly with AFS:

• The eol extension requires more permissions than might be expected. See issue2569.

4. Apple Filing Protocol (AFP)

It seems like AFP occasionally (for example here) has been confused with AFS. Some AFP issues has thus incorrectly has been attributed to AFS.