Provided by: e2fsprogs_1.47.0-1ubuntu1_amd64 bug

NAME

       debugfs - ext2/ext3/ext4 file system debugger

SYNOPSIS

       debugfs [ -DVwcin ] [ -b blocksize ] [ -s superblock ] [ -f cmd_file ] [ -R request ] [ -d
       data_source_device ] [ -z undo_file ] [ 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 a block device (e.g., /dev/sdXX) or a file containing the file system.

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.

       -n     Disables metadata checksum verification.  This should only be used if  you  believe
              the metadata to be correct despite the complaints of e2fsprogs.

       -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  file
              systems  with significant corruption, but because of this, catastrophic mode forces
              the file system 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 (in bytes) for the file system, rather  than
              detecting  the correct block size automatically.  (This option is rarely needed; it
              is used primarily when the file system is extremely badly damaged/corrupted.)

       -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 file system).  If you specify the -s option, you must also provide
              the  blocksize  of  the  file  system  via  the -b option.   (This option is rarely
              needed;  it  is  used  primarily  when  the  file   system   is   extremely   badly
              damaged/corrupted.)

       -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.

       -z undo_file
              Before overwriting a file system block, write the old contents of the block  to  an
              undo  file.   This undo file can be used with e2undo(8) to restore the old contents
              of the file system should something go wrong.  If the empty string is passed as the
              undo_file  argument,  the  undo  file  will  be  written  to  a file named debugfs-
              device.e2undo in the directory specified  via  the  E2FSPROGS_UNDO_DIR  environment
              variable.

              WARNING: The undo file cannot be used to recover from a power or system crash.

SPECIFYING FILES

       Many  debugfs commands take a filespec as an argument to specify an inode (as opposed to a
       pathname) in the file system 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 file system 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 filespec
              Print the blocks used by the inode filespec to stdout.

       bmap [ -a ] filespec logical_block [physical_block]
              Print or set the physical block number corresponding to the  logical  block  number
              logical_block  in the inode filespec.  If the -a flag is specified, try to allocate
              a block if necessary.

       block_dump '[ -x ] [-f filespec] block_num
              Dump the file system 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.  If the -x option is specified, the block is interpreted  as
              an extended attribute block and printed to show the structure of extended attribute
              data structures.

       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.

       copy_inode source_inode destination_inode
              Copy the contents of the inode structure in source_inode and use  it  to  overwrite
              the inode structure at destination_inode.

       dirsearch filespec filename
              Search the directory filespec for filename.

       dirty [-clean]
              Mark  the  file  system  as dirty, so that the superblocks will be written on exit.
              Additionally, clear the superblock's valid flag, or set it if -clean is specified.

       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 [mmp_block]
              Display  the  multiple-mount  protection  (mmp)  field  values.   If  mmp_block  is
              specified  then  verify  and  dump  the  MMP  values  from  the given block number,
              otherwise use the s_mmp_block field  in  the  superblock  to  locate  and  use  the
              existing MMP block.

       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 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  file
              system  data  structures.    Hence,  the  values  displayed  may not necessarily by
              accurate and does not indicate a problem or corruption in the file system.)

       dump_unused
              Dump unused blocks which contain non-null bytes.

       ea_get [-f outfile]|[-xVC] [-r] filespec attr_name
              Retrieve the value of the extended attribute attr_name in  the  file  filespec  and
              write it either to stdout or to outfile.

       ea_list filespec
              List the extended attributes associated with the file filespec to standard output.

       ea_set [-f infile] [-r] filespec attr_name attr_value
              Set  the  value  of  the  extended  attribute attr_name in the file filespec to the
              string value attr_value or read it from infile.

       ea_rm filespec attr_names...
              Remove the extended attribute attr_name from the file filespec.

       expand_dir filespec
              Expand the directory filespec.

       fallocate filespec start_block [end_block]
              Allocate  and  map  uninitialized  blocks  into  filespec  between  logical   block
              start_block  and end_block, inclusive.  If end_block is not supplied, this function
              maps until it runs out of free disk blocks or the maximum  file  size  is  reached.
              Existing mappings are left alone.

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

       get_quota quota_type id
              Display quota information for given quota type (user, group, or project) and ID.

       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 [-b]|[-e]|[-x] filespec
              Print the contents of the inode data structure in hex and  ASCII  format.   The  -b
              option  causes the command to only dump the contents of the i_blocks array.  The -e
              option causes the command to only dump the contents of the extra inode space, which
              is  used  to store in-line extended attributes. The -x option causes the command to
              dump the extra inode space interpreted and extended attributes.  This is useful  to
              debug corrupted inodes containing extended attributes.

       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.

       journal_close
              Close the open journal.

       journal_open [-c] [-v ver] [-f ext_jnl]
              Opens  the journal for reading and writing.  Journal checksumming can be enabled by
              supplying -c; checksum formats 2 and 3 can be selected  with  the  -v  option.   An
              external journal can be loaded from ext_jnl.

       journal_run
              Replay all transactions in the open journal.

       journal_write [-b blocks] [-r revoke] [-c] file
              Write  a  transaction  to  the open journal.  The list of blocks to write should be
              supplied as a comma-separated list in  blocks;  the  blocks  themselves  should  be
              readable  from  file.   A  list  of  blocks  to  revoke can be supplied as a comma-
              separated list in revoke.  By default, a commit record is written at the  end;  the
              -c switch writes an uncommitted transaction.

       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 file system.

       list_quota quota_type
              Display quota information for given quota type (user, group, or project).

       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 [-acsOS] [-b block] [-n num_trans ] [-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 -S option causes logdump to print the contents of the journal superblock.

              The  -a  option  causes  the logdump to print the contents of all of the descriptor
              blocks.  The -b option causes logdump to print all journal records  that  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.

              The -O option causes logdump to display old (checkpointed) journal  entries.   This
              can  be  used to try to track down journal problems even after the journal has been
              replayed.

              The -n option causes logdump to continue past a journal block which  is  missing  a
              magic  number.   Instead, it will stop only when the entire log is printed or after
              num_trans transactions.

       ls [-l] [-c] [-d] [-p] [-r] filespec
              Print a listing of the files  in  the  directory  filespec.   The  -c  flag  causes
              directory  block  checksums  (if  present)  to be displayed.  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.  The -r flag will force the printing
              of the filename, even if it is encrypted.

       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] [-d image_filename] [-s superblock] [-z undo_file] device
              Open  a  file  system for editing.  The -f flag forces the file system to be opened
              even if there are some unknown or incompatible file  system  features  which  would
              normally  prevent  the  file system from being opened.  The -e flag causes the file
              system to be opened in exclusive mode.  The -b, -c, -d, -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 file system.

       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.

       set_current_time time
              Set current time in seconds since Unix  epoch  to  use  when  setting  file  system
              fields.

       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_debugfs_params
              Display debugfs parameters such as information about currently opened file system.

       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.

       supported_features
              Display file system features supported by this version of debugfs.

       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 file system 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 file system 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)