Provided by: e2fsprogs_1.42-1ubuntu2_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.

       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 file
              Clear the contents of the inode file.

       dirsearch filespec filename
              Search the directory filespec for filename.

       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  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.

       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.)

       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
              Free the inode specified by filespec.

       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.

       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 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, the  journal
              inode  as  specified  in  the  superblock.  However, this can be
              overridden with the -i option, which uses an inode specifier  to
              specify  the journal to be used.  A 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 [-l] [-d] [-p] filespec
              Print a listing of the files in the directory filespec.  The  -l
              flag  will  list files using a more verbose format.  The -d flag
              will list deleted entries in the directory.  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.

       modify_inode filespec
              Modify  the  contents  of  the  inode  structure  in  the  inode
              filespec.

       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 inode_num ...
              Take the requested list of inode numbers, and print a listing of
              pathnames to those inodes.

       open  [-w]  [-e]  [-f]  [-i]  [-c]  [-D] [-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.

       pwd    Print the current working directory.

       quit   Quit debugfs

       rdump directory destination
              Recursively  dump  directory  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.

       seti filespec
              Mark inode filespec as in use in the inode bitmap.

       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

       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

       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

       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.

       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 num> [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
              Create a file in the filesystem named  out_file,  and  copy  the
              contents of source_file into the destination file.

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,        list_directory,        show_inode_info,
              list_deleted_inodes, 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)