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List:       opensolaris-help
Subject:    Re: [osol-help] Disabling  SUNWattr_ro and SUNWattr_rw
From:       "Richard L. Hamilton" <rlhamil () smart ! net>
Date:       2011-01-13 4:05:08
Message-ID: 1209248589.71294920340101.JavaMail.Twebapp () sf-app1
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> Hello,
> I was wondering if there is any way to disable the
> SUNWattr_ro and SUNWattr_rw file attributes in
> OpenSolaris.
> 
> I am receiving some permission denied error messages
> assocaited with SUNWattr_ro on some files.  It has
> been suggested that there is a way to disable them,
> or remove them, etc.  However I have been unable to
> find any information about doing so.
> 
> Example:
> admin@server1:/ztank/temp# touch test
> admin@server1:/ztank/temp# runat test ls -l
> total 2
> -r--r--r-- 1 root root 84 Jan 11 11:58 SUNWattr_ro
> -rw-r--r-- 1 root root 408 Jan 11 11:58 SUNWattr_rw
> 
> 
> Thanks in advance,
> 
> Shain

They are not "real" extended attributes, rather, they are
_views_ of the _extensible_ attributes (approximately 2 read-only and 15
short attributes of well-defined data types, typically maintained
by zfs itself, or by the CIFS server, or set aside for zfs implementations
on other OS's), made visible to existing utilities in the form of SUNWattr_ro
and SUNWattr_rw.  They have the appearance of _extended_ attributes (filescapable of \
holding large content, existing within a single-level hidden directory associated \
with each file or directory on a filesystem capable of supporting them), but they \
cannot be created or deleted, because they're just a view, and their contents is \
managed by the system.  Only the SUNWattr_rw can be written (I think), as a way of \
allowing backup/restore utilities to preserve user-writable extensible attributes (if \
I understand correctly). And I wouldn't be surprised if when writing SUNWattr_rw, the \
system enforces correct semantics of the contents.

See http://arc.opensolaris.org/caselog/PSARC/2007/315/spec.final.txt

for a detailed description of extensible attributes and how _views_
of them are made visible as the (synthetic, system managed)
_extended_ attribute files SUNWattr_ro and SUNWattr_rw.

I'm guessing that whatever your problem is, either there's a bug, or
some utility is trying to create or delete SUNWattr_ro or SUNWattr_rw
explicitly, or to write to SUNWattr_ro.

If that's not causing the utility to fail, but just causing error messages,
then it should be safe to just ignore the error messages.

In the spec I cited above, there are only two attributes in SUNWattr_ro,
and the fact that they are read-only should not be a problem for
utilities such as tar or cpio, because they're not something that
would be meaningful to preserve anyway.

There is a filesystem-level zfs attribute "xattr", which I gather
controls whether _extended_ attributes are allowed.  I don't know
if it affects the _extensible_ attributes or their views SUNWattr_ro and
SUNWattr_rw, nor whether it can be used if extended attributes are
already present on the filesystem.  I would not recommend using it
to attempt to silence the error messages you're seeing.  I don't think
there's any other supported way to tell the OS not to cause the
situation that produces the error messages you're seeing.

You say you're receiving permission denied messages, but you don't
actually say what you're doing.  So I can only guess that you might
be using some utility like tar or cpio in a version that's aware of
extended attributes but doesn't know not to try to restore SUNWattr_ro.
If you said in more detail what you're doing that causes the error message,
it might be possible for someone to give you a more specific response.
But I suspect the "proper" solution is to either fix whatever program you're
using (rather than the OS itself), or to simply ignore the error messages.
-- 
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