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SubjectACL's, Capabilities, Priv-Bits & other fs meta-data
DateMon, 02 Mar 1998 02:00:36 -0800
FromJim Dennis <>
  All,

  I realize I'm probably just displaying my ignorance here but I have
  a question about how we intend to extend ext2fs (or ext3?) to 
  support ACL's, "Orange-Book" privilege bits, capabilities, and/or
  other file/directory meta data.

  I don't like the idea of significantly enlarging the inode structure 
  to support these sorts of features, particularly if only a small 
  percentage of the files on any given system will be using them.
  (It seems likely to me that Unix/Linux sysadmins will continue to 
  use traditional Unix permissions bits wherever possible, and only
  *resort* to ACL's (etc) when then *need* to do so.

  One thought occurred to me:  what if we only add a pointer to 
  a "resource fork" (not really much like the Apple/MacOS "resource fork"
  -- so perhaps we should call it something different, like the 
  meta data field).  I guess this would actually be a pointer to another
  inode -- one normally had no directory entries (links).  Then arbitrary
  amounts of meta data could be encoded into the data on this other 
  "fork."

  This would be extensible -- and would have no effect on the inodes
  that had no "meta-data" associated with them (presumably the majority
  of files and directories for the majority of fs').

  Another (probably uglier) way that occurs to me is to have a "shadow"
  fs with meta data in it.  I haven't thought about that beyond just 
  mentioning it here.  I suppose an advantage of a "shadowfs" is that
  it would allow one to add/overlay ACL's and other semantics over 
  existing fs types.  It might offer some marginal performance advantages
  (if one made it a point to put the shadow/overlay on a different spindle
  from it's associated fs.

  As usual I'm speaking on a purely theoretical basis here.  My real 
  question is:  how were we planning on adding most of these extensions
  to the fs'.  It seems like I've read about a bunch of different patches
  to ext2fs (from GNU HURD's "watchdog" file system objects to Andrew
  Morgan's "privs" to several ACL's systems and a few logging and/or
  journaling fs').

--
Jim Dennis  (800) 938-4078		consulting@starshine.org
Proprietor, Starshine Technical Services:  http://www.starshine.org
        PGP  1024/2ABF03B1 Jim Dennis <jim@starshine.org>
        Key fingerprint =  2524E3FEF0922A84  A27BDEDB38EBB95A 



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