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