The ext4 filesystem supports extended attributes, which are name-value pairs that can be associated with a file. - chatGPT

If you need to move files with xattr between filesystems (e.g., from ZFS to ext4), you may encounter compatibility issues. Use tools like tar or rsync with –xattrs to preserve attributes.

Notes

Custom attribute are of the form user.tag and the prefix user is not customizable, only the tag part, eg trying to set:

• xattr -w blake3.h 1234 src/blake3.rb => [Errno 95] Operation not supported
• xattr -w user.blake3 1234 src/blake3.rb => works fine

Lang support

• Ruby - ffi-xattr - unmaintained