*BASH User Commands Ubuntu 10.04.4 LTS Server coreutils
GNU/Linux
DEBUGFS(8)                                                          DEBUGFS(8)



NAME
       debugfs - ext2/ext3/ext4 file system debugger

SYNOPSIS
       debugfs  [ -Vwci ] [ -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.

       -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 com-
       mand cd.

COMMANDS
       This is a list of the commands which debugfs supports.

       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.

       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_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  dis-
              play 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 esystem 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.

       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.

       freei filespec
              Free the inode specified by filespec.

       help   Print a list of commands understood by debugfs(8).

       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 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.

       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>]  [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] [-b blocksize] [-s superblock] 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, -i, -s, and -w options
              behave the same as the command-line options to debugfs.

       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_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-
              spec.

       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(8) program always pipes the output of the some com-
              mands  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 1.41.11         March 2010                        DEBUGFS(8)