Provided by: e2fsprogs_1.42-1ubuntu2_amd64 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)