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 'e' attribute indicates that the file is using extents for mapping
  77 the blocks on disk.  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 The 'I' attribute is used by the htree code to indicate that a directory
  83 is being indexed using hashed trees.  It may not be set or reset using
  84 .BR chattr (1),
  85 although it can be displayed by
  86 .BR lsattr (1).
  87 .PP
  88 The 'H' attribute indicates the file is storing its blocks in units of the
  89 filesystem blocksize instead of in units of sectors, and means that the file
  90 is (or at one time was) larger than 2TB.  It may not be set or reset using
  91 .BR chattr (1),
  92 although it can be displayed by
  93 .BR lsattr (1).
  94 .PP
  95 A file with the `i' attribute cannot be modified: it cannot be deleted or
  96 renamed, no link can be created to this file and no data can be written
  97 to the file.  Only the superuser or a process possessing the
  98 CAP_LINUX_IMMUTABLE capability can set or clear this attribute.
  99 .PP
 100 A file with the `j' attribute has all of its data written to the ext3
 101 journal before being written to the file itself, if the filesystem is
 102 mounted with the "data=ordered" or "data=writeback" options.  When the
 103 filesystem is mounted with the "data=journal" option all file data
 104 is already journalled and this attribute has no effect.
 105 Only the superuser or a process possessing the CAP_SYS_RESOURCE
 106 capability can set or clear this attribute.
 107 .PP
 108 When a file with the `s' attribute set is deleted, its blocks are zeroed
 109 and written back to the disk.  Note: please make sure to read the bugs
 110 and limitations section at the end of this document.
 111 .PP
 112 When a file with the `S' attribute set is modified,
 113 the changes are written synchronously on the disk; this is equivalent to
 114 the `sync' mount option applied to a subset of the files.
 115 .PP
 116 A directory with the 'T' attribute will be deemed to be the top of
 117 directory hierarchies for the purposes of the Orlov block allocator.
 118 This is a hint to the block allocator used by ext3 and ext4 that the
 119 subdirectories under this directory are not related, and thus should be
 120 spread apart for allocation purposes.   For example it is a very good
 121 idea to set the 'T' attribute on the /home directory, so that /home/john
 122 and /home/mary are placed into separate block groups.  For directories
 123 where this attribute is not set, the Orlov block allocator will try to
 124 group subdirectories closer together where posible.
 125 .PP
 126 A file with the 't' attribute will not have a partial block fragment at
 127 the end of the file merged with other files (for those filesystems which
 128 support tail-merging).  This is necessary for applications such as LILO
 129 which read the filesystem directly, and which don't understand tail-merged
 130 files.  Note: As of this writing, the ext2 or ext3 filesystems do not
 131 (yet, except in very experimental patches) support tail-merging.
 132 .PP
 133 When a file with the `u' attribute set is deleted, its contents are
 134 saved.  This allows the user to ask for its undeletion.  Note: please
 135 make sure to read the bugs and limitations section at the end of this
 136 document.
 137 .PP
 138 The 'X' attribute is used by the experimental compression patches to
 139 indicate that a raw contents of a compressed file can be accessed
 140 directly.  It currently may not be set or reset using
 141 .BR chattr (1),
 142 although it can be displayed by
 143 .BR lsattr (1).
 144 .PP
 145 The 'Z' attribute is used by the experimental compression patches to
 146 indicate a compressed file is dirty.  It may not be set or reset using
 147 .BR chattr (1),
 148 although it can be displayed by
 149 .BR lsattr (1).
 150 .PP
 151 .SH AUTHOR
 152 .B chattr
 153 was written by Remy Card <Remy.Card@linux.org>.  It is currently being
 154 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
 155 .SH BUGS AND LIMITATIONS
 156 The `c', 's',  and `u' attributes are not honored
 157 by the ext2 and ext3 filesystems as implemented in the current mainline
 158 Linux kernels.    These attributes may be implemented
 159 in future versions of the ext2 and ext3 filesystems.
 160 .PP
 161 The `j' option is only useful if the filesystem is mounted as ext3.
 162 .PP
 163 The `D' option is only useful on Linux kernel 2.5.19 and later.
 164 .SH AVAILABILITY
 165 .B chattr
 166 is part of the e2fsprogs package and is available from
 167 http://e2fsprogs.sourceforge.net.
 168 .SH SEE ALSO
 169 .BR lsattr (1)