debugfs


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  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 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  filesys-
              tem).   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.

       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 com-
       mand 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 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 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.

       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 allo-
              cate 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  per-
              missions  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  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
              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
              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>]  [out-
       put_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 file-
              spec.

       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  filesys-

       pwd    Print the current working directory.

       quit   Quit debugfs

       rdump directory destination
              Recursively dump directory and all its contents (including regu-
              lar 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 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.

       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 com-
              mand: 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 dis-
              played 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  file-
              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 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)



E2fsprogs version 1.42           November 2011                      DEBUGFS(8)
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