Thank you Tim,
I've read some related document and checked the source code. I understand
the determining access of posix acl clearly now. :)
Thanks for your enthusiastic help.
John
On Tue, 8 Jan 2002, Timothy Shimmin wrote:
> Hi John,
>
> On Wed, Dec 26, 2001 at 11:01:38AM +0800, niu@xxxxxxxxxxxxxxxxxxxx wrote:
> > Hi XFS guys,
> >
> > I'm using ACLs of linux XFS to manage my share files. Recently, I
> > encounter a confused problem: If a user belongs to multiple groups, and
> > all the groups are set ALCs to a file(directory), then how about the
> > user's permission to this file(directory)?
> >
> > I've do some test, the result looks like that: for file, the user's
> > permission is the combination(OR operation) of his groups ACLs; but
> > for directory, the user's permission looks weird, it's neither OR
> > operation nor AND operation of his groups ACLs.
> >
> > Could you explain more details about the rule of XFS ACLs? Thank you.
> >
> > John
> >
> >
> XFS ACLs are based on the Posix 1003.1e draft standard 17 (Section 23).
> This withdrawn Posix ACL standard can be downloaded at:
> http://wt.xpilot.org/posix.1e/download.html
> Andreas Grünbacher's site: http://acl.bestbits.at/
> is also a useful resource.
>
> So if you are going to use ACLs it is worth doing some ACL reading :)
>
> I don't fully understand your problem.
> Perhaps you can list the set of commands that you used
> and the output from them.
>
> Checkout the section 23.1.2 (Relationship with File permission Bits)
> to see how the ACL ACEs match up with the standard file permission
> bits.
> In particular one would note that the group permission bits
> reflect the Mask permission bits when a Mask ACE exists
> and Section B.23.3.6 (in Annex B) discusses reasons why this
> scheme was chosen.
>
> (Also worthy of note, is that if you create a file whose parent dir
> has a default ACL, then it's ACE permissions are set by the
> _intersection_ of the respective default ACEs permission bits and
> the mode bits of the parameter to open/creat.
> If you have a MASK ACE (section 5.3.1.2), then the
> ACE permissions on the new file will have a MASK ACE equal to
> the intersection of the default MASK ACE permission bits
> and the standard group permission bits of the parameter to open/creat.)
>
> --Tim
>
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