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