On Wed, 17 Oct 2007, Nathan Scott wrote:
attr(1) is intended only for XFS - it is an IRIX-compatibility
command, and there are parts of the tool that only work on the
XFS filesystem (in particular, those options that deal with the
ROOT namespace are XFS-specific).
In that case, a note near the top alerting users of other FSes that This Is
Not The Command You Seek is probably a good idea. Something like "Users of
other filesystems probably want getfattr(1) and setfattr(1)." (This just
moves the bit you mentioned:
"This document describes the attr command, which is mostly compatible
with the IRIX command of the same name. It is thus aimed specifically
at users of the XFS filesystem - for filesystem independent extended
attribute manipulation, consult the getfattr(1) and setfattr(1) docu‐
mentation."
up the page, to where I'd've actually seen it!
I do agree it would be useful to document this somewhere - the attr(5)
man page is a general discussion of extended attributes on Linux, so it
would seem a suitable place - do you want to send me a patch?
I think the paragraph on FILESYSTEM DIFFERENCES in attr(5) would be
a better spot.
I suggest you add the sentence "Some file systems, such as ext2/3 and
reiserfs 3, require the filesystem to be mounted with the mount option
`user_xattr' in order for extended user attributes to be used." to the end
of the first paragraph.
Also, the 6th paragraph of the DESCRIPTION section is woefully out of date:
not only does it not mention reiserfs, but it implies you need to patch the
kernel, which hasn't been true for a long time. I suggest you change it to:
"Currently, support for extended attributes is implemented on Linux by the
ext2, ext3, ext4, XFS, JFS and reiserfs filesystems." I don't know if there
are others.
As far as "filesystem differences" go, I don't know what the situation is
with reiserfs or JFS. Since xattrs are implemented as files in reiserfs, it
would seem there isn't a size limit; I can't find one in the source. JFS
xattrs seem to have 255 byte names and 65535 byte values, from looking at
the code:
http://lxr.linux.no/source/fs/jfs/jfs_xattr.h
And perhaps also on the getfattr/setfattr man pages?
I think not. These pages already direct the user to attr(5), and putting the
remark in more than one place makes it more likely to become misleading
later on if and when it's no longer true.
--
http://rrt.sc3d.org/ | motive, n. a mental wolf in moral wool (Bierce)
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