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DEBUGFS(8)                  System Manager's Manual                 DEBUGFS(8)



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] [-f] [-i] [-c] [-b blocksize] [-s superblock] device
              Open  a filesystem for editing.  The -w flag causes the filesys-
              tem to be opened for writing.  The -f flag forces the filesystem
              to  be  opened  even  if  there are some unknown or incompatible
              filesystem features which would normally prevent the  filesystem
              from  being  opened.   The -c, -b, -i, and -s options behave the
              same as those to debugfs itself.

       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 <tytsoATmit.edu>.

SEE ALSO
       dumpe2fs(8), e2fsck(8), mke2fs(8)



E2fsprogs version 1.37            March 2005                        DEBUGFS(8)