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