On Aug 02, 2009 12:41 -0700, Linda A. Walsh wrote: > Would it be possible to get tar to copy (or ignore) file attributes, and > to copy ACL's if they exist ( maybe via an option)? > > Some attr's I really like to keep on files, and end up having to use > something a host of different utils (depending on fs and os), but > common examples are the '+d" 'don't dump' attribute -- something I > usually set on large multi-gig scratch files I'm using for testing, > or temporary copies of DVD's on my disk (certainly don't need to back > up such things as the original is the DVD -- much better than trying > to use backup space).
This kind of file attribute (nodump, immutable, append-only, etc) isn't backed up by tar yet, not even the ones that already back up extended attributes (e.g. recent RHEL/FC tar with xattr patches). > ACL's -- those would be most useful for me under Cygin-Windows. Cygwin > uses Windows ACL's itself for emulating the standard unix rwx permisions > for groups, but native ACL's are also set for existing files that it > would be nice if they could be kept in a backup. (Since Window's > native backup seems to die about 165G into its backup attempt (I think > it is actually 'finished', and dies during final 'housekeeping'). ACLs are backed up by the patched RHEL/FC tar programs. > I'd rather save it in a standard format if I could (i.e. tar)... > > Of course on Win, it has underlying file attribs as well, (HSRA...) It might be possible that DOS/FAT/NTFS already have extensions to backup/restore these attributes via tar, in which case they should be extended to handle extN/xfs/jfs/btrfs/reiserfs attributes (which are implemented with a common getattr() interface). > Dunno how possible...but certainly the ext2+xfs 'd' attribs > and file ACLS's -- it'd be up to the support libraries to actually > be available to be able to pull the values in so 'tar' could store > them. > > _Maybe_ for Backwards compat such info could be stored ahead of a file > in some variation of the filename? Like if fn="filename", then store > attribs in .filename#.%attrib%.<hex-numbered ext>, if need to avoid fn > collisions? Probably the easiest way to back these attributes up would be to store them in a "virtual" extended attribute in a very simple (text?) encoding. One possibility is like: attributes=nodump,immutable and if such an xattr is seen during file restore it is converted to the apropriate bitfields and set via setattr(). Cheers, Andreas -- Andreas Dilger Sr. Staff Engineer, Lustre Group Sun Microsystems of Canada, Inc.
