Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages

  
 
  

home | help
DEBUGFS(8)		    System Manager's Manual		    DEBUGFS(8)

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  com-
	      plaints of e2fsprogs.

       -c     Specifies	 that the file system should be	opened in catastrophic
	      mode, in which the inode and group bitmaps  are  not  read  ini-
	      tially.	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 alloca-
	      tion 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  automati-
	      cally.  (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  filesys-
	      tem).   If  you specify the -s option, you must also provide the
	      blocksize	of the filesystem via the -b option.   (This option is
	      rarely  needed; it is used primarily when	the file system	is ex-
	      tremely 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  in-
       ode  (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  com-
       mand 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 log-
	      ical 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	 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.	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 spec-
	      ified,  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 filesystem 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	 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.)

       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 log-
	      ical 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  map-
	      pings are	left alone.

       feature [fs_feature] [-fs_feature] ...
	      Set or clear various filesystem features in the superblock.  Af-
	      ter setting or clearing any filesystem features  that  were  re-
	      quested, 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 di-
	      rectory.	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	 allo-
	      cate 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  lo-
	      cated.   The second optional argument mode specifies the permis-
	      sions 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  sys-
	      tem.   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 con-
	      tents 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 ex-
	      tended attributes.  This is useful  to  debug  corrupted	inodes
	      containing extended attributes.

       imap filespec
	      Print the	location of the	inode data structure (in the inode ta-
	      ble) 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	struc-
	      tures; 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 filesystem.

       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]  [-i  filespec]  [-f journal_file] [out-
       put_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	 jour-
	      nal superblock.

	      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 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) jour-
	      nal entries.  This can be	used to	 try  to  track	 down  journal
	      problems even after the journal has been replayed.

       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  dis-
	      played.  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 file-
	      names.  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 use-
	      ful for this purpose if the files	were  deleted  using  ext3  or
	      ext4,  since the inode's data blocks are no longer available af-
	      ter the inode is released.

       modify_inode filespec
	      Modify the contents of the inode structure in  the  inode	 file-
	      spec.  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  ma-
	      jor 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 filesystem for editing.  The -f flag forces the filesys-
	      tem 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,	-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 di-
	      rectories) into the named	destination, which should be an	exist-
	      ing directory on the native filesystem.

       rm pathname
	      Unlink pathname.	If this	causes the inode pointed to  by	 path-
	      name  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 argu-
	      ment  count is present, then count blocks	starting at block num-
	      ber 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	avail-
	      able as set_bg.

       set_current_time	time
	      Set current time in seconds since	Unix epoch to use when setting
	      filesystem 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 com-
	      mand: set_mmp_value -l Also available as smmp.

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

       show_debugfs_params
	      Display  debugfs	parameters such	as information about currently
	      opened filesystem.

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

       stat filespec
	      Display the contents of the inode	structure of the  inode	 file-
	      spec.

       supported_features
	      Display  filesystem  features  supported	by this	version	of de-
	      bugfs.

       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 file-
	      spec.

ENVIRONMENT VARIABLES
       DEBUGFS_PAGER, PAGER
	      The debugfs program always pipes the output of the some commands
	      through  a  pager	 program.   These  commands  include: show_su-
	      per_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	 vari-
	      able, 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 dis-
	      playing  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)

E2fsprogs version 1.45.7	 January 2021			    DEBUGFS(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SPECIFYING FILES | COMMANDS | ENVIRONMENT VARIABLES | AUTHOR | SEE ALSO

Want to link to this manual page? Use this URL:
<https://www.freebsd.org/cgi/man.cgi?query=debugfs&sektion=8&manpath=FreeBSD+13.0-RELEASE+and+Ports>

home | help