NAME
       debugfs - ext2/ext3 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 file system.
       device  is  the special file corresponding to the device containing the
       ext2 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, rather than the default (1).  If  you  give  a  -s
              option, you must also give a -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  Close the currently open file system.

       clri file
              Clear the contents of the inode file.

       dump [-p] filspec 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.

       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] 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.

       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.

       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.

       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), e2fsck(8), mke2fs(8)

E2fsprogs version 1.39             May 2006                         DEBUGFS(8)