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author | Nathan Scott <nathans@sgi.com> | 2002-02-25 22:10:22 +0000 |
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committer | Nathan Scott <nathans@sgi.com> | 2002-02-25 22:10:22 +0000 |
commit | c82edc1013cf28a096cb8f5ba21c28d3e9312227 (patch) | |
tree | 5a2c12886725666beddf1aaf8cdf20e474359ebc /man/man5 | |
parent | a87485aca58ea2236b31b0c0b8e438b3d967709b (diff) | |
download | attr-c82edc1013cf28a096cb8f5ba21c28d3e9312227.tar.gz |
Merge of xfs-cmds-2.4.18:slinx:111138a by nathans.
bump to version 2.0.0 for extended attribute and other interface changes.
incorporate new code, docs, etc from ext2/ext3 project.
Diffstat (limited to 'man/man5')
-rw-r--r-- | man/man5/Makefile | 48 | ||||
-rw-r--r-- | man/man5/attr.5 | 110 |
2 files changed, 158 insertions, 0 deletions
diff --git a/man/man5/Makefile b/man/man5/Makefile new file mode 100644 index 0000000..b81e765 --- /dev/null +++ b/man/man5/Makefile @@ -0,0 +1,48 @@ +# +# Copyright (c) 2000 Silicon Graphics, Inc. All Rights Reserved. +# +# This program is free software; you can redistribute it and/or modify it +# under the terms of version 2 of the GNU General Public License as +# published by the Free Software Foundation. +# +# This program is distributed in the hope that it would be useful, but +# WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. +# +# Further, this software is distributed without any warranty that it is +# free of the rightful claim of any third person regarding infringement +# or the like. Any license provided herein, whether implied or +# otherwise, applies only to this software file. Patent licenses, if +# any, provided herein do not apply to combinations of this program with +# other software, or any other product whatsoever. +# +# You should have received a copy of the GNU General Public License along +# with this program; if not, write the Free Software Foundation, Inc., 59 +# Temple Place - Suite 330, Boston MA 02111-1307, USA. +# +# Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy, +# Mountain View, CA 94043, or: +# +# http://www.sgi.com +# +# For further information regarding this notice, see: +# +# http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/ +# + +TOPDIR = ../.. +include $(TOPDIR)/include/builddefs + +MAN_SECTION = 5 + +MAN_PAGES = $(shell echo *.$(MAN_SECTION)) +MAN_DEST = $(PKG_MAN_DIR)/man$(MAN_SECTION) +LSRCFILES = $(MAN_PAGES) + +default install : $(MAN_PAGES) + +include $(BUILDRULES) + +install-dev : default + $(INSTALL) -m 755 -d $(MAN_DEST) + $(INSTALL_MAN) diff --git a/man/man5/attr.5 b/man/man5/attr.5 new file mode 100644 index 0000000..4d82071 --- /dev/null +++ b/man/man5/attr.5 @@ -0,0 +1,110 @@ +.\" +.\" Extended attributes manual page +.\" +.\" (C) Andreas Gruenbacher, 2000 +.\" (C) Silicon Graphics Inc, 2001 +.\" +.TH ATTR 5 +.SH NAME +Extended attributes +.SH DESCRIPTION +Extended attributes are name:value pairs associated permanently with +files and directories, similar to the environment strings associated +with a process. +An attribute may be defined or undefined. +If it is defined, its value may be empty or non-empty. +.PP +Extended attributes are extensions to the normal attributes which are +associated with all inodes in the system (i.e. the +.BR stat (2) +data). +They are often used to provide additional functionality +to a filesystem \- for example, additional security features such as +Access Control Lists (ACLs) may be implemented using extended attributes. +.PP +Users with search access to a file or directory may retrieve a list of +attribute names defined for that file or directory. +.PP +Extended attributes are accessed as atomic objects. +Reading retrieves the whole value of an attribute and stores it in a buffer. +Writing replaces any previous value with the new value. +.PP +Currently, support for extended attributes is implemented on Linux by +the ext2, ext3 and XFS filesystem patches, which can be downloaded from +.B http://acl.bestbits.at/ +and +.B http://oss.sgi.com/projects/xfs/ +respectively. +.SH EXTENDED ATTRIBUTE NAMESPACES +Attribute names are zero-terminated strings and typically have a short +(filesystem dependent) length. +The attribute name is always specified in the full +.IR namespace.attribute +form, eg. +.I user.mime_type +or +.IR system.posix_acl_access . +.PP +The namespace mechanism is used to define different classes of extended +attributes. +These different classes exist for several reasons, e.g. the permissions +and capabilities required for manipulating extended attributes of one +namespace may differ to another. +They have also been used to distinguish filesystem-specific attribute +names from canonical, filesystem-independent attribute names. +.PP +The extended attribute namespace is always specified as the first +component of the name. +This greatly simplifies certain operations, and provides a consistent, +explicit interface for all operations. +.PP +Extended +.I user +attributes may be assigned to files and directories for storing arbitrary +additional information such as the mime type, character set or encoding +of a file. +User attributes are subject to the same permissions as the contents of a file. +The file owner can decide who is allowed to read and/or set these attributes. +.PP +Extended +.I system +attributes are used by the kernel to store system objects such as +Access Control Lists and Capabilities. +Read and write access permissions to system attributes +depend on the policy implemented for each system attribute implemented +in the kernel. +.PP +Additional types of extended attributes with different access permissions, +such as attributes that are accessible only to processes trusted by the +kernel, may be added in the future. +.SH FILESYSTEM DIFFERENCES +The kernel and the filesystem may place limits on the maximum number +and size of extended attributes that can be associated with a file. +.PP +In the current ext2 and ext3 filesystem implementations, all extended +attributes must fit on a single filesystem block (1024, 2048 or 4096 bytes, +depending on the block size specified when the filesystem +was created). This limit may be removed in a future version. +Device special files cannot be associated with extended user attributes +(but they may be associated with extended system attributes). Permissions +of device special files define access to the devices rather than to the +device special files. +.PP +In the XFS filesystem implementation, there is no practical limit on the +number of extended attributes associated with a file, and the algorithms +used to store extended attribute information on disk are scalable (stored +either inline in the inode, as an extent, or in a B+ tree). +XFS allows extended attributes to be associated with device inodes. +.SH ADDITIONAL NOTES +Since the filesystems on which extended attributes are stored might also +be used on architectures with a different byte order and machine word +size, care should be taken to store attribute values in an architecture +independent format. +.SH AUTHORS +Andreas Gruenbacher, +.RI < a.gruenbacher@computer.org > +and the SGI XFS development team, +.RI < linux-xfs@oss.sgi.com >. +.SH SEE ALSO +getfattr(1), +setfattr(1). |