FUSE mount and ACLs

[ThomasWaldmann]

See there for basic issue: jborg/attic#266

[ThomasWaldmann]

Aside from the stuff mentioned there, 2 more ideas (more or less dirty ones):

1. At "borg create" time, we exclude "system.posix_acl_*" from the backed up xattrs. Removing this exclude would put these xattrs into the archive, so a FUSE mount on the system where the data came from would likely work. Whether this would work on another system is questionable. At "borg extract" time, these 2 xattrs would need to get excluded from xattr restoration as the ACL restoration sets them up.
2. Alternatively, we maybe could use the ACL stored in the archive, apply it to a temporary file and read the xattr value we need from there.

[enkore]

I'd say the right way would be to add a platform API that is invoked by FuseOperations.getattr with the item and EntryAttributes, so it can try restoring the ACL which might not work everywhere with FUSE (thinking about osxfuse, dokany).

acl_set_fuse(item, entry)

ACLs differ by platform anyway. Linux and BSD should be compatible (POSIX ACL?), otherwise no compat.

• osx: acl_extended
• bsd: acl_default, _access, _nfs4
• linux: acl_default, _access
• win: win_dacl, win_sacl

[ThomasWaldmann]

This is blocked by missing system-specific low-level ACL functions (one that can convert an ACL text representation into the expected binary representation).

FUSE (libfuse) should implement that, but did not yet.

Do a web search "libfuse ACL" for already existing discussion.

[ThomasWaldmann]

Kernel 4.9 FUSE News:

• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=60bcc88ad185d512f5718f2f8dcccb483ea8fb73
• https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=703c73629f93464ce210f5ad92d0c1fb95bfbadf

[ThomasWaldmann]

Does anybody know what userspace changes this needs?
updated libraries?
if so: which libraries, which minimum version?

As Debian 8 will likely have kernel 4.9 (which likely will be a LTS kernel), this might get interesting soon.

[infectormp]

kernel 4.9 was added to longterm supported kernels https://lkml.org/lkml/2017/1/19/339

[ThomasWaldmann]

libfuse:

https://github.com/libfuse/libfuse/blob/master/ChangeLog.rst

libfuse/libfuse@e16fdc0

So it looks like one needs libfuse 3.0.

[ThomasWaldmann]

https://packages.debian.org/search?keywords=libfuse&searchon=names&suite=testing&section=all

And next debian release does not (yet?) have libfuse 3. :-(