Provided by: e2fsprogs_1.42.13-1ubuntu1_i386 bug

NAME

       debugfs - ext2/ext3/ext4 file system debugger

SYNOPSIS

       debugfs [ -DVwci ] [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [
       -R request ] [ -d data_source_device ] [ device ]

DESCRIPTION

       The debugfs program is an interactive file system debugger. It  can  be
       used  to  examine  and  change the state of an ext2, ext3, or ext4 file
       system.
       device is the special file corresponding to the device  containing  the
       file system (e.g /dev/hdXX).

OPTIONS

       -w     Specifies  that  the  file system should be opened in read-write
              mode.  Without this option, the file system is opened  in  read-
              only mode.

       -c     Specifies  that the file system should be opened in catastrophic
              mode, in  which  the  inode  and  group  bitmaps  are  not  read
              initially.   This can be useful for filesystems with significant
              corruption, but because of this, catastrophic  mode  forces  the
              filesystem to be opened read-only.

       -i     Specifies  that  device represents an ext2 image file created by
              the e2image program.  Since the ext2 image  file  only  contains
              the   superblock,   block  group  descriptor,  block  and  inode
              allocation bitmaps, and the inode table, many  debugfs  commands
              will  not  function  properly.  Warning: no safety checks are in
              place, and debugfs may fail in interesting ways if commands such
              as   ls,   dump,   etc.   are   tried   without  specifying  the
              data_source_device using the -d option.  debugfs is a  debugging
              tool.  It has rough edges!

       -d data_source_device
              Used  with  the  -i  option,  specifies  that data_source_device
              should be used when reading blocks not found in the  ext2  image
              file.  This includes data, directory, and indirect blocks.

       -b blocksize
              Forces  the  use  of  the  given block size for the file system,
              rather than detecting the correct block size as normal.

       -s superblock
              Causes the file system superblock to  be  read  from  the  given
              block  number,  instead of using the primary superblock (located
              at  an  offset  of  1024  bytes  from  the  beginning   of   the
              filesystem).   If  you  specify  the  -s  option,  you must also
              provide the blocksize of the filesystem via the -b option.

       -f cmd_file
              Causes debugfs to read in commands from  cmd_file,  and  execute
              them.   When  debugfs  is  finished executing those commands, it
              will exit.

       -D     Causes debugfs to open the device using  Direct  I/O,  bypassing
              the  buffer cache.  Note that some Linux devices, notably device
              mapper as of this writing, do not support Direct I/O.

       -R request
              Causes debugfs to execute the single command request,  and  then
              exit.

       -V     print the version number of debugfs and exit.

SPECIFYING FILES

       Many  debugfs  commands  take  a  filespec as an argument to specify an
       inode (as opposed to a pathname) in the filesystem which  is  currently
       opened  by  debugfs.   The  filespec  argument  may be specified in two
       forms.  The first form is an inode number surrounded by angle brackets,
       e.g.,  <2>.  The second form is a pathname; if the pathname is prefixed
       by a forward slash ('/'), then it is interpreted relative to  the  root
       of  the  filesystem  which is currently opened by debugfs.  If not, the
       pathname is interpreted relative to the current  working  directory  as
       maintained  by  debugfs.   This  may  be  modified by using the debugfs
       command cd.

COMMANDS

       This is a list of the commands which debugfs supports.

       blocks filespace
              Print the blocks used by the inode filespec to stdout.

       bmap filespec logical_block
              Print the physical block number  corresponding  to  the  logical
              block number logical_block in the inode filespec.

       block_dump [-f filespec] block_num
              Dump  the  filesystem  block given by block_num in hex and ASCII
              format to the console.  If the -f option is specified, the block
              number is relative to the start of the given filespec.

       cat filespec
              Dump the contents of the inode filespec to stdout.

       cd filespec
              Change the current working directory to filespec.

       chroot filespec
              Change the root directory to be the directory filespec.

       close [-a]
              Close  the  currently  open  file  system.   If the -a option is
              specified, write out any changes to  the  superblock  and  block
              group  descriptors to all of the backup superblocks, not just to
              the master superblock.

       clri filespec
              Clear the contents of the inode filespec.

       dirsearch filespec filename
              Search the directory filespec for filename.

       dirty  Mark the filesystem as dirty, so that the  superblocks  will  be
              written on exit.

       dump [-p] filespec out_file
              Dump  the  contents  of  the  inode  filespec to the output file
              out_file.  If the -p option is given set the  owner,  group  and
              permissions information on out_file to match filespec.

       dump_mmp
              Display the multiple-mount protection (mmp) field values.

       dx_hash [-h hash_alg] [-s hash_seed] filename
              Calculate  the  directory  hash of filename.  The hash algorithm
              specified with -h may be legacy, half_md4,  or  tea.   The  hash
              seed specified with -s must be in UUID format.

       dump_extents [-n] [-l] filespec
              Dump  the  the  extent  tree of the inode filespec.  The -n flag
              will cause dump_extents to only display the  interior  nodes  in
              the  extent  tree.   The -l flag will cause dump_extents to only
              display the leaf nodes in the extent tree.

              (Please note that the length and range of blocks  for  the  last
              extent in an interior node is an estimate by the extents library
              functions, and is not  stored  in  filesystem  data  structures.
              Hence,  the values displayed may not necessarily by accurate and
              does not indicate a problem or corruption in the file system.)

       expand_dir filespec
              Expand the directory filespec.

       feature [fs_feature] [-fs_feature] ...
              Set or clear various  filesystem  features  in  the  superblock.
              After  setting  or  clearing  any  filesystem features that were
              requested, print the current state  of  the  filesystem  feature
              set.

       filefrag [-dvr] filespec
              Print the number of contiguous extents in filespec.  If filespec
              is a directory and the -d option is not specified, filefrag will
              print  the  number  of  contiguous  extents for each file in the
              directory.  The -v option will cause filefrag  print  a  tabular
              listing  of  the  contiguous extents in the file.  The -r option
              will cause filefrag to do a recursive listing of the directory.

       find_free_block [count [goal]]
              Find the  first  count  free  blocks,  starting  from  goal  and
              allocate it.  Also available as ffb.

       find_free_inode [dir [mode]]
              Find  a  free  inode and allocate it.  If present, dir specifies
              the inode number of the directory  which  the  inode  is  to  be
              located.   The  second  optional  argument  mode  specifies  the
              permissions of the new inode.  (If the directory bit is  set  on
              the  mode,  the  allocation  routine will function differently.)
              Also available as ffi.

       freeb block [count]
              Mark the block number block as not allocated.  If  the  optional
              argument  count  is present, then count blocks starting at block
              number block will be marked as not allocated.

       freefrag [-c chunk_kb]
              Report free space  fragmentation  on  the  currently  open  file
              system.  If the -c option is specified then the filefrag command
              will print how many free chunks of size chunk_kb can be found in
              the  file  system.  The chunk size must be a power of two and be
              larger than the file system block size.

       freei filespec [num]
              Free the inode specified by filespec.  If num is specified, also
              clear num-1 inodes after the specified inode.

       help   Print a list of commands understood by debugfs.

       htree_dump filespec
              Dump  the  hash-indexed  directory  filespec,  showing  its tree
              structure.

       icheck block ...
              Print a listing of the inodes which use the one or  more  blocks
              specified on the command line.

       inode_dump filespec
              Print  the contents of the inode data structure in hex and ASCII
              format.

       imap filespec
              Print the location of the inode data  structure  (in  the  inode
              table) of the inode filespec.

       init_filesys device blocksize
              Create an ext2 file system on device with device size blocksize.
              Note that this  does  not  fully  initialize  all  of  the  data
              structures; to do this, use the mke2fs(8) program.  This is just
              a call to the low-level library, which sets  up  the  superblock
              and block descriptors.

       kill_file filespec
              Deallocate  the  inode  filespec and its blocks.  Note that this
              does not remove any directory entries (if any)  to  this  inode.
              See the rm(1) command if you wish to unlink a file.

       lcd directory
              Change  the  current working directory of the debugfs process to
              directory on the native filesystem.

       ln filespec dest_file
              Create a link named dest_file which is a hard link to  filespec.
              Note this does not adjust the inode reference counts.

       logdump [-acs] [-b block] [-i filespec] [-f journal_file] [output_file]
              Dump  the  contents  of  the ext3 journal.  By default, dump the
              journal inode as specified in the superblock.  However, this can
              be  overridden  with the -i option, which dumps the journal from
              the internal inode given by filespec.  A regular file containing
              journal data can be specified using the -f option.  Finally, the
              -s option utilizes the backup information in the  superblock  to
              locate the journal.

              The  -a  option causes the logdump program to print the contents
              of all of the descriptor blocks.  The -b option  causes  logdump
              to  print  all  journal  records that are refer to the specified
              block.  The -c option will print out the contents of all of  the
              data blocks selected by the -a and -b options.

       ls [-d] [-l] [-p] filespec
              Print  a listing of the files in the directory filespec.  The -d
              flag will list deleted entries in the directory.   The  -l  flag
              will  list  files using a more verbose format.  The -p flag will
              list the files in a format which  is  more  easily  parsable  by
              scripts,  as  well as making it more clear when there are spaces
              or other non-printing characters at the end of filenames.

       list_deleted_inodes [limit]
              List deleted inodes, optionally limited to those deleted  within
              limit seconds ago.  Also available as lsdel.

              This  command  was  useful  for  recovering from accidental file
              deletions for ext2  file  systems.   Unfortunately,  it  is  not
              useful  for this purpose if the files were deleted using ext3 or
              ext4, since the inode's data  blocks  are  no  longer  available
              after the inode is released.

       modify_inode filespec
              Modify  the  contents  of  the  inode  structure  in  the  inode
              filespec.  Also available as mi.

       mkdir filespec
              Make a directory.

       mknod filespec [p|[[c|b] major minor]]
              Create a special device file (a named pipe, character  or  block
              device).   If  a  character  or  block device is to be made, the
              major and minor device numbers must be specified.

       ncheck [-c] inode_num ...
              Take the requested list of inode numbers, and print a listing of
              pathnames to those inodes.  The -c flag will enable checking the
              file type information in the directory entry  to  make  sure  it
              matches the inode's type.

       open [-weficD] [-b blocksize] [-s superblock] device
              Open   a  filesystem  for  editing.   The  -f  flag  forces  the
              filesystem to be opened  even  if  there  are  some  unknown  or
              incompatible  filesystem  features  which would normally prevent
              the filesystem from  being  opened.   The  -e  flag  causes  the
              filesystem  to be opened in exclusive mode.  The -b, -c, -i, -s,
              -w, and -D options behave the same as the  command-line  options
              to debugfs.

       punch filespec start_blk [end_blk]
              Delete  the  blocks  in  the  inode  ranging  from  start_blk to
              end_blk.  If end_blk is omitted then this command will  function
              as  a  truncate  command; that is, all of the blocks starting at
              start_blk through to the end of the file will be deallocated.

       symlink filespec target
              Make a symbolic link.

       pwd    Print the current working directory.

       quit   Quit debugfs

       rdump directory[...] destination
              Recursively dump directory, or multiple directories, and all its
              contents  (including  regular  files,  symbolic links, and other
              directories) into the named  destination,  which  should  be  an
              existing directory on the native filesystem.

       rm pathname
              Unlink  pathname.   If  this  causes  the  inode  pointed  to by
              pathname to have no other references, deallocate the file.  This
              command functions as the unlink() system call.

       rmdir filespec
              Remove the directory filespec.

       setb block [count]
              Mark  the  block  number  block  as  allocated.  If the optional
              argument count is present, then count blocks starting  at  block
              number block will be marked as allocated.

       set_block_group bgnum field value
              Modify the block group descriptor specified by bgnum so that the
              block group  descriptor  field  field  has  value  value.   Also
              available as set_bg.

       seti filespec [num]
              Mark  inode  filespec  as in use in the inode bitmap.  If num is
              specified, also set num-1 inodes after the specified inode.

       set_inode_field filespec field value
              Modify the inode specified by filespec so that the  inode  field
              field has value value.  The list of valid inode fields which can
              be set via this command can be displayed by using  the  command:
              set_inode_field -l Also available as sif.

       set_mmp_value field value
              Modify  the multiple-mount protection (MMP) data so that the MMP
              field field has value value.  The list of valid MMP fields which
              can  be  set  via  this  command  can  be displayed by using the
              command: set_mmp_value -l Also available as smmp.

       set_super_value field value
              Set the superblock field field to  value.   The  list  of  valid
              superblock  fields  which  can  be  set  via this command can be
              displayed  by  using  the  command:  set_super_value   -l   Also
              available as ssv.

       show_super_stats [-h]
              List  the  contents  of  the  super  block  and  the block group
              descriptors.  If the -h  flag  is  given,  only  print  out  the
              superblock contents. Also available as stats.

       stat filespec
              Display  the  contents  of  the  inode  structure  of  the inode
              filespec.

       testb block [count]
              Test if the block number block is marked  as  allocated  in  the
              block  bitmap.   If the optional argument count is present, then
              count blocks starting at block number block will be tested.

       testi filespec
              Test if the inode filespec is marked as allocated in  the  inode
              bitmap.

       undel <inode_number> [pathname]
              Undelete the specified inode number (which must be surrounded by
              angle brackets) so that it and its blocks are marked in use, and
              optionally  link  the recovered inode to the specified pathname.
              The e2fsck command should always be run after  using  the  undel
              command to recover deleted files.

              Note that if you are recovering a large number of deleted files,
              linking the inode to a directory may require the directory to be
              expanded, which could allocate a block that had been used by one
              of the yet-to-be-undeleted files.  So it is  safer  to  undelete
              all of the inodes without specifying a destination pathname, and
              then in a separate pass, use the debugfs link  command  to  link
              the  inode  to  the destination pathname, or use e2fsck to check
              the filesystem and link all  of  the  recovered  inodes  to  the
              lost+found directory.

       unlink pathname
              Remove  the  link  specified by pathname to an inode.  Note this
              does not adjust the inode reference counts.

       write source_file out_file
              Copy the contents of source_file into a  newly-created  file  in
              the filesystem named out_file.

       zap_block [-f filespec] [-o offset] [-l length] [-p pattern] block_num

       Overwrite the block specified by
              block_num  with zero (NUL) bytes, or if -p is given use the byte
              specified by pattern.  If -f is given then block_num is relative
              to  the  start  of  the  file  given by filespec.  The -o and -l
              options limit the range of bytes to zap to the specified  offset
              and length relative to the start of the block.

       zap_block [-f filespec] [-b bit] block_num
              Bit-flip  portions  of  the physical block_num.  If -f is given,
              then block_num is a logical  block  relative  to  the  start  of
              filespec.

ENVIRONMENT VARIABLES

       DEBUGFS_PAGER, PAGER
              The debugfs program always pipes the output of the some commands
              through   a   pager   program.     These    commands    include:
              show_super_stats  (stats),  list_directory (ls), show_inode_info
              (stat),  list_deleted_inodes  (lsdel),  and   htree_dump.    The
              specific  pager  can  explicitly  specified by the DEBUGFS_PAGER
              environment variable, and  if  it  is  not  set,  by  the  PAGER
              environment variable.

              Note that since a pager is always used, the less(1) pager is not
              particularly appropriate, since  it  clears  the  screen  before
              displaying  the  output of the command and clears the output the
              screen when the pager is exited.  Many users prefer to  use  the
              less(1)  pager for most purposes, which is why the DEBUGFS_PAGER
              environment variable is available to override the  more  general
              PAGER environment variable.

AUTHOR

       debugfs was written by Theodore Ts'o <tytso@mit.edu>.

SEE ALSO

       dumpe2fs(8), tune2fs(8), e2fsck(8), mke2fs(8), ext4(5)