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 file system
   5 .SH SYNOPSIS
   6 .B chattr
   7 [
   8 .B \-RVf
   9 ]
  10 [
  11 .B \-v
  12 .I version
  13 ]
  14 [
  15 .B \-p
  16 .I project
  17 ]
  18 [
  19 .I mode
  20 ]
  21 .I files...
  22 .SH DESCRIPTION
  23 .B chattr
  24 changes the file attributes on a Linux file system.
  25 .PP
  26 The format of a symbolic mode is +-=[aAcCdDeijsStTu].
  27 .PP
  28 The operator '+' causes the selected attributes to be added to the
  29 existing attributes of the files; '-' causes them to be removed; and '='
  30 causes them to be the only attributes that the files have.
  31 .PP
  32 The letters 'aAcCdDeijsStTu' select the new attributes for the files:
  33 append only (a),
  34 no atime updates (A),
  35 compressed (c),
  36 no copy on write (C),
  37 no dump (d),
  38 synchronous directory updates (D),
  39 extent format (e),
  40 immutable (i),
  41 data journalling (j),
  42 secure deletion (s),
  43 synchronous updates (S),
  44 no tail-merging (t),
  45 top of directory hierarchy (T),
  46 and undeletable (u).
  47 .PP
  48 The following attributes are read-only, and may be listed by
  49 .BR lsattr (1)
  50 but not modified by chattr:
  51 compression error (E),
  52 huge file (h),
  53 indexed directory (I),
  54 inline data (N),
  55 compression raw access (X),
  56 and compressed dirty file (Z).
  57 .PP
  58 Not all flags are supported or utilized by all filesystems; refer to
  59 filesystem-specific man pages such as
  60 .BR btrfs (5),
  61 .BR ext4 (5),
  62 and
  63 .BR xfs (5)
  64 for more filesystem-specific details.
  65 .SH OPTIONS
  66 .TP
  67 .B \-R
  68 Recursively change attributes of directories and their contents.
  69 .TP
  70 .B \-V
  71 Be verbose with chattr's output and print the program version.
  72 .TP
  73 .B \-f
  74 Suppress most error messages.
  75 .TP
  76 .BI \-v " version"
  77 Set the file's version/generation number.
  78 .TP
  79 .BI \-p " project"
  80 Set the file's project number.
  81 .SH ATTRIBUTES
  82 A file with the 'a' attribute set can only be open in append mode for writing.
  83 Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE
  84 capability can set or clear this attribute.
  85 .PP
  86 When a file with the 'A' attribute set is accessed, its atime record is
  87 not modified.  This avoids a certain amount of disk I/O for laptop
  88 systems.
  89 .PP
  90 A file with the 'c' attribute set is automatically compressed on the disk
  91 by the kernel.  A read from this file returns uncompressed data.  A write to
  92 this file compresses data before storing them on the disk.  Note: please
  93 make sure to read the bugs and limitations section at the end of this
  94 document.
  95 .PP
  96 A file with the 'C' attribute set will not be subject to copy-on-write
  97 updates.  This flag is only supported on file systems which perform
  98 copy-on-write.  (Note: For btrfs, the 'C' flag should be
  99 set on new or empty files.  If it is set on a file which already has
 100 data blocks, it is undefined when the blocks assigned to the file will
 101 be fully stable.  If the 'C' flag is set on a directory, it will have no
 102 effect on the directory, but new files created in that directory will
 103 have the No_COW attribute set.)
 104 .PP
 105 A file with the 'd' attribute set is not candidate for backup when the
 106 .BR dump (8)
 107 program is run.
 108 .PP
 109 When a directory with the 'D' attribute set is modified,
 110 the changes are written synchronously on the disk; this is equivalent to
 111 the 'dirsync' mount option applied to a subset of the files.
 112 .PP
 113 The 'e' attribute indicates that the file is using extents for mapping
 114 the blocks on disk.  It may not be removed using
 115 .BR chattr (1).
 116 .PP
 117 The 'E' attribute is used by the experimental encryption patches to
 118 indicate that the file has been encrypted.  It may not be
 119 set or reset using
 120 .BR chattr (1),
 121 although it can be displayed by
 122 .BR lsattr (1).
 123 .PP
 124 The 'h' attribute indicates the file is storing its blocks in units of the
 125 filesystem blocksize instead of in units of sectors, and means that the file
 126 is (or at one time was) larger than 2TB.  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 A file with the 'i' attribute cannot be modified: it cannot be deleted or
 132 renamed, no link can be created to this file and no data can be written
 133 to the file.  Only the superuser or a process possessing the
 134 CAP_LINUX_IMMUTABLE capability can set or clear this attribute.
 135 .PP
 136 The 'I' attribute is used by the htree code to indicate that a directory
 137 is being indexed using hashed trees.  It may not be set or reset using
 138 .BR chattr (1),
 139 although it can be displayed by
 140 .BR lsattr (1).
 141 .PP
 142 A file with the 'j' attribute has all of its data written to the ext3
 143 or ext4 journal before being written to the file itself, if the filesystem
 144 is mounted with the "data=ordered" or "data=writeback" options.  When the
 145 filesystem is mounted with the "data=journal" option all file data
 146 is already journalled and this attribute has no effect.  Only
 147 the superuser or a process possessing the CAP_SYS_RESOURCE
 148 capability can set or clear this attribute.
 149 .PP
 150 A file with the 'N' attribute set indicates that the file has data
 151 stored inline, within the inode itself. It may not be set or reset using
 152 .BR chattr (1),
 153 although it can be displayed by
 154 .BR lsattr (1).
 155 .PP
 156 When a file with the 's' attribute set is deleted, its blocks are zeroed
 157 and written back to the disk.  Note: please make sure to read the bugs
 158 and limitations section at the end of this document.
 159 .PP
 160 When a file with the 'S' attribute set is modified,
 161 the changes are written synchronously on the disk; this is equivalent to
 162 the 'sync' mount option applied to a subset of the files.
 163 .PP
 164 A file with the 't' attribute will not have a partial block fragment at
 165 the end of the file merged with other files (for those filesystems which
 166 support tail-merging).  This is necessary for applications such as LILO
 167 which read the filesystem directly, and which don't understand tail-merged
 168 files.  Note: As of this writing, the ext2 or ext3 filesystems do not
 169 (yet, except in very experimental patches) support tail-merging.
 170 .PP
 171 A directory with the 'T' attribute will be deemed to be the top of
 172 directory hierarchies for the purposes of the Orlov block allocator.
 173 This is a hint to the block allocator used by ext3 and ext4 that the
 174 subdirectories under this directory are not related, and thus should be
 175 spread apart for allocation purposes.   For example it is a very good
 176 idea to set the 'T' attribute on the /home directory, so that /home/john
 177 and /home/mary are placed into separate block groups.  For directories
 178 where this attribute is not set, the Orlov block allocator will try to
 179 group subdirectories closer together where possible.
 180 .PP
 181 When a file with the 'u' attribute set is deleted, its contents are
 182 saved.  This allows the user to ask for its undeletion.  Note: please
 183 make sure to read the bugs and limitations section at the end of this
 184 document.
 185 .PP
 186 The 'X' attribute is used by the experimental compression patches to
 187 indicate that the raw contents of a compressed file can be accessed
 188 directly.  It currently may not be set or reset using
 189 .BR chattr (1),
 190 although it can be displayed by
 191 .BR lsattr (1).
 192 .PP
 193 The 'Z' attribute is used by the experimental compression patches to
 194 indicate a compressed file is dirty.  It may not be set or reset using
 195 .BR chattr (1),
 196 although it can be displayed by
 197 .BR lsattr (1).
 198 .PP
 199 .SH AUTHOR
 200 .B chattr
 201 was written by Remy Card <Remy.Card@linux.org>.  It is currently being
 202 maintained by Theodore Ts'o <tytso@alum.mit.edu>.
 203 .SH BUGS AND LIMITATIONS
 204 The 'c', 's',  and 'u' attributes are not honored
 205 by the ext2, ext3, and ext4 filesystems as implemented in the current
 206 mainline Linux kernels.
 207 .PP
 208 The 'j' option is only useful if the filesystem is mounted as ext3 or ext4.
 209 .PP
 210 The 'D' option is only useful on Linux kernel 2.5.19 and later.
 211 .SH AVAILABILITY
 212 .B chattr
 213 is part of the e2fsprogs package and is available from
 214 http://e2fsprogs.sourceforge.net.
 215 .SH SEE ALSO
 216 .BR lsattr (1),
 217 .BR btrfs (5),
 218 .BR ext4 (5),
 219 .BR xfs (5).