misc/chattr.1.in

   1 .\" -*- nroff -*-
   2 .TH CHATTR 1 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
   3 .SH NAME
   4 chattr \- change file attributes on a Linux second extended file system
   5 .SH SYNOPSIS
   6 .B chattr
   7 [
   8 .B \-RV
   9 ]
  10 [
  11 .B \-v
  12 .I version
  13 ]
  14 [
  15 .I mode
  16 ]
  17 .I files...
  18 .SH DESCRIPTION
  19 .B chattr
  20 changes the file attributes on a Linux second extended file system.
  21 .PP
  22 The format of a symbolic mode is +-=[ASacDdIijsTtu].
  23 .PP
  24 The operator `+' causes the selected attributes to be added to the
  25 existing attributes of the files; `-' causes them to be removed; and
  26 `=' causes them to be the only attributes that the files have.
  27 .PP
  28 The letters `acdijsuADST' select the new attributes for the files:
  29 append only (a), compressed (c), no dump (d), immutable (i),
  30 data journalling (j), secure deletion (s), no tail-merging (t),
  31 undeletable (u), no atime updates (A), synchronous directory updates (D),
  32 synchronous updates (S), and top of directory hierarchy (T).
  33 .SH OPTIONS
  34 .TP
  35 .B \-R
  36 Recursively change attributes of directories and their contents.
  37 Symbolic links encountered during recursive directory traversals are
  38 ignored.
  39 .TP
  40 .B \-V
  41 Be verbose with chattr's output and print the program version.
  42 .TP
  43 .BI \-v " version"
  44 Set the file's version/generation number.
  45 .SH ATTRIBUTES
  46 When a file with the 'A' attribute set is accessed, its atime record is
  47 not modified.  This avoids a certain amount of disk I/O for laptop
  48 systems.
  49 .PP
  50 A file with the `a' attribute set can only be open in append mode for writing.
  51 Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE
  52 capability can set or clear this attribute.
  53 .PP
  54 A file with the `c' attribute set is automatically compressed on the disk
  55 by the kernel.  A read from this file returns uncompressed data.  A write to
  56 this file compresses data before storing them on the disk.  Note: please
  57 make sure to read the bugs and limitations section at the end of this
  58 document.
  59 .PP
  60 When a directory with the `D' attribute set is modified,
  61 the changes are written synchronously on the disk; this is equivalent to
  62 the `dirsync' mount option applied to a subset of the files.
  63 .PP
  64 A file with the `d' attribute set is not candidate for backup when the
  65 .BR dump (8)
  66 program is run.
  67 .PP
  68 The 'E' attribute is used by the experimental compression patches to
  69 indicate that a compressed file has a compression error.  It may not be
  70 set or reset using
  71 .BR chattr (1),
  72 although it can be displayed by
  73 .BR lsattr (1).
  74 .PP
  75 The 'I' attribute is used by the htree code to indicate that a directory
  76 is behind indexed using hashed trees.  It may not be set or reset using
  77 .BR chattr (1),
  78 although it can be displayed by
  79 .BR lsattr (1).
  80 .PP
  81 A file with the `i' attribute cannot be modified: it cannot be deleted or
  82 renamed, no link can be created to this file and no data can be written
  83 to the file.  Only the superuser or a process possessing the
  84 CAP_LINUX_IMMUTABLE capability can set or clear this attribute.
  85 .PP
  86 A file with the `j' attribute has all of its data written to the ext3
  87 journal before being written to the file itself, if the filesystem is
  88 mounted with the "data=ordered" or "data=writeback" options.  When the
  89 filesystem is mounted with the "data=journal" option all file data
  90 is already journalled and this attribute has no effect.
  91 Only the superuser or a process possessing the CAP_SYS_RESOURCE
  92 capability can set or clear this attribute.
  93 .PP
  94 When a file with the `s' attribute set is deleted, its blocks are zeroed
  95 and written back to the disk.  Note: please make sure to read the bugs
  96 and limitations section at the end of this document.
  97 .PP
  98 When a file with the `S' attribute set is modified,
  99 the changes are written synchronously on the disk; this is equivalent to
 100 the `sync' mount option applied to a subset of the files.
 101 .PP
 102 A directory with the 'T' attribute will be deemed to be the top of
 103 directory hierarchies for the purposes of the Orlov block allocator
 104 (which is used in on systems with Linux 2.5.46 or later).
 105 .PP
 106 A file with the 't' attribute will not have a partial block fragment at
 107 the end of the file merged with other files (for those filesystems which
 108 support tail-merging).  This is necessary for applications such as LILO
 109 which read the filesystem directly, and which don't understand tail-merged
 110 files.  Note: As of this writing, the ext2 or ext3 filesystems do not
 111 (yet, except in very experimental patches) support tail-merging.
 112 .PP
 113 When a file with the `u' attribute set is deleted, its contents are
 114 saved.  This allows the user to ask for its undeletion.  Note: please
 115 make sure to read the bugs and limitations section at the end of this
 116 document.
 117 .PP
 118 The 'X' attribute is used by the experimental compression patches to
 119 indicate that a raw contents of a compressed file can be accessed
 120 directly.  It currently may not be set or reset using
 121 .BR chattr (1),
 122 although it can be displayed by
 123 .BR lsattr (1).
 124 .PP
 125 The 'Z' attribute is used by the experimental compression patches to
 126 indicate a compressed file is dirty.  It may not be set or reset using
 127 .BR chattr (1),
 128 although it can be displayed by
 129 .BR lsattr (1).
 130 .PP
 131 .SH AUTHOR
 132 .B chattr
 133 was written by Remy Card <Remy.Card@linux.org>.  It is currently being
 134 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
 135 .SH BUGS AND LIMITATIONS
 136 The `c', 's',  and `u' attributes are not honored
 137 by the ext2 and ext3 filesystems as implemented in the current mainline
 138 Linux kernels.    These attributes may be implemented
 139 in future versions of the ext2 and ext3 filesystems.
 140 .PP
 141 The `j' option is only useful if the filesystem is mounted as ext3.
 142 .PP
 143 The `D' option is only useful on Linux kernel 2.5.19 and later.
 144 .SH AVAILABILITY
 145 .B chattr
 146 is part of the e2fsprogs package and is available from
 147 http://e2fsprogs.sourceforge.net.
 148 .SH SEE ALSO
 149 .BR lsattr (1)