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author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-24 04:52:22 +0000 |
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committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-05-24 04:52:22 +0000 |
commit | 7f3caba522f4d24764f29d83aa2de9198bb7f01c (patch) | |
tree | 66b798ea74302325d6a5c11df044cbe4bb845af1 /man7/xattr.7 | |
parent | Adding upstream version 6.7. (diff) | |
download | manpages-7f3caba522f4d24764f29d83aa2de9198bb7f01c.tar.xz manpages-7f3caba522f4d24764f29d83aa2de9198bb7f01c.zip |
Adding upstream version 6.8.upstream/6.8upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'man7/xattr.7')
-rw-r--r-- | man7/xattr.7 | 180 |
1 files changed, 0 insertions, 180 deletions
diff --git a/man7/xattr.7 b/man7/xattr.7 deleted file mode 100644 index c90aaf8..0000000 --- a/man7/xattr.7 +++ /dev/null @@ -1,180 +0,0 @@ -.\" Extended attributes manual page -.\" -.\" Copyright (C) 2000, 2002, 2007 Andreas Gruenbacher <agruen@suse.de> -.\" Copyright (C) 2001, 2002, 2004, 2007 Silicon Graphics, Inc. -.\" All rights reserved. -.\" -.\" SPDX-License-Identifier: GPL-2.0-or-later -.\" -.TH xattr 7 2023-10-31 "Linux man-pages 6.7" -.SH NAME -xattr \- 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. -.P -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\[em]for example, additional security features such as -Access Control Lists (ACLs) may be implemented using extended attributes. -.P -Users with search access to a file or directory may use -.BR listxattr (2) -to retrieve a list of attribute names defined for that file or directory. -.P -Extended attributes are accessed as atomic objects. -Reading -.RB ( getxattr (2)) -retrieves the whole value of an attribute and stores it in a buffer. -Writing -.RB ( setxattr (2)) -replaces any previous value with the new value. -.P -Space consumed for extended attributes may be counted towards the disk quotas -of the file owner and file group. -.SS Extended attribute namespaces -Attribute names are null-terminated strings. -The attribute name is always specified in the fully qualified -.I namespace.attribute -form, for example, -.IR user.mime_type , -.IR trusted.md5sum , -.IR system.posix_acl_access , -or -.IR security.selinux . -.P -The namespace mechanism is used to define different classes of extended -attributes. -These different classes exist for several reasons; -for example, the permissions -and capabilities required for manipulating extended attributes of one -namespace may differ to another. -.P -Currently, the -.IR security , -.IR system , -.IR trusted , -and -.I user -extended attribute classes are defined as described below. -Additional classes may be added in the future. -.SS Extended security attributes -The security attribute namespace is used by kernel security modules, -such as Security Enhanced Linux, and also to implement file capabilities (see -.BR capabilities (7)). -Read and write access permissions to security attributes depend on the -policy implemented for each security attribute by the security module. -When no security module is loaded, all processes have read access to -extended security attributes, and write access is limited to processes -that have the -.B CAP_SYS_ADMIN -capability. -.SS System extended attributes -System extended attributes are used by the kernel to store system -objects such as Access Control Lists. -Read and write -access permissions to system attributes depend on the policy implemented -for each system attribute implemented by filesystems in the kernel. -.SS Trusted extended attributes -Trusted extended attributes are visible and accessible only to processes that -have the -.B CAP_SYS_ADMIN -capability. -Attributes in this class are used to implement mechanisms in user -space (i.e., outside the kernel) which keep information in extended attributes -to which ordinary processes should not have access. -.SS User extended attributes -User extended 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. -The access permissions for user -attributes are defined by the file permission bits: -read permission is required to retrieve the attribute value, -and writer permission is required to change it. -.P -The file permission bits of regular files and directories are -interpreted differently from the file permission bits of special files -and symbolic links. -For regular files and directories the file -permission bits define access to the file's contents, while for device special -files they define access to the device described by the special file. -The file permissions of symbolic links are not used in access checks. -These differences would allow users to consume filesystem resources in -a way not controllable by disk quotas for group or world writable -special files and directories. -.P -For this reason, -user extended attributes are allowed only for regular files and directories, -and access to user extended attributes is restricted to the -owner and to users with appropriate capabilities for directories with the -sticky bit set (see the -.BR chmod (1) -manual page for an explanation of the sticky bit). -.SS 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. -The VFS-imposed limits on attribute names and values are 255 bytes -and 64\ kB, respectively. -The list of attribute names that -can be returned is also limited to 64\ kB -(see BUGS in -.BR listxattr (2)). -.P -Some filesystems, such as Reiserfs (and, historically, ext2 and ext3), -require the filesystem to be mounted with the -.B user_xattr -mount option in order for user extended attributes to be used. -.P -In the current ext2, ext3, and ext4 filesystem implementations, -the total bytes used by the names and values of all of a file's -extended attributes must fit in a single filesystem block (1024, 2048 -or 4096 bytes, depending on the block size specified when the -filesystem was created). -.P -In the Btrfs, XFS, and Reiserfs filesystem implementations, 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. -.P -In the JFS, XFS, and Reiserfs filesystem implementations, -the limit on bytes used in an EA value is the ceiling imposed by the VFS. -.P -In the Btrfs filesystem implementation, -the total bytes used for the name, value, and implementation overhead bytes -is limited to the filesystem -.I nodesize -value (16\ kB by default). -.SH STANDARDS -Extended attributes are not specified in POSIX.1, but some other systems -(e.g., the BSDs and Solaris) provide a similar feature. -.SH 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. -.P -This page was formerly named -.BR attr (5). -.\" .SH AUTHORS -.\" Andreas Gruenbacher, -.\" .RI < a.gruenbacher@bestbits.at > -.\" and the SGI XFS development team, -.\" .RI < linux-xfs@oss.sgi.com >. -.SH SEE ALSO -.BR attr (1), -.BR getfattr (1), -.BR setfattr (1), -.BR getxattr (2), -.BR ioctl_iflags (2), -.BR listxattr (2), -.BR removexattr (2), -.BR setxattr (2), -.BR acl (5), -.BR capabilities (7), -.BR selinux (8) |