{
    "content": [
        {
            "type": "text",
            "text": "# debugfs (man)\n\n## NAME\n\ndebugfs - ext2/ext3/ext4 file system debugger\n\n## SYNOPSIS\n\ndebugfs  [  -DVwcin  ] [ -b blocksize ] [ -s superblock ] [ -f cmdfile ] [ -R request ] [ -d\ndatasourcedevice ] [ -z undofile ] [ device ]\n\n## DESCRIPTION\n\nThe debugfs program is an interactive file system debugger. It can be  used  to  examine  and\nchange the state of an ext2, ext3, or ext4 file system.\n\n## TLDR\n\n> An interactive ext2/ext3/ext4 filesystem debugger.\n\n- Open the filesystem in read only mode:\n  `debugfs {{/dev/sdXN}}`\n- Open the filesystem in read write mode:\n  `debugfs -w {{/dev/sdXN}}`\n- Read commands from a specified file, execute them and then exit:\n  `debugfs -f {{path/to/cmd_file}} {{/dev/sdXN}}`\n- [Interactive] View the filesystem stats in debugfs console:\n  `stats`\n- [Interactive] Close the filesystem:\n  `close -a`\n- [Interactive] List all available commands:\n  `lr`\n\n*Source: tldr-pages*\n\n## Sections\n\n- **NAME**\n- **SYNOPSIS**\n- **DESCRIPTION**\n- **OPTIONS** (1 subsections)\n- **SPECIFYING FILES**\n- **COMMANDS** (5 subsections)\n- **ENVIRONMENT VARIABLES** (1 subsections)\n- **AUTHOR**\n- **SEE ALSO**\n\nUse structuredContent.sections for detailed options, examples, and full documentation.\n"
        }
    ],
    "structuredContent": {
        "command": "debugfs",
        "section": "",
        "mode": "man",
        "summary": "debugfs - ext2/ext3/ext4 file system debugger",
        "synopsis": "debugfs  [  -DVwcin  ] [ -b blocksize ] [ -s superblock ] [ -f cmdfile ] [ -R request ] [ -d\ndatasourcedevice ] [ -z undofile ] [ device ]",
        "tldr_summary": "An interactive ext2/ext3/ext4 filesystem debugger.",
        "tldr_examples": [
            {
                "description": "Open the filesystem in read only mode",
                "command": "debugfs {{/dev/sdXN}}"
            },
            {
                "description": "Open the filesystem in read write mode",
                "command": "debugfs -w {{/dev/sdXN}}"
            },
            {
                "description": "Read commands from a specified file, execute them and then exit",
                "command": "debugfs -f {{path/to/cmd_file}} {{/dev/sdXN}}"
            },
            {
                "description": "[Interactive] View the filesystem stats in debugfs console",
                "command": "stats"
            },
            {
                "description": "[Interactive] Close the filesystem",
                "command": "close -a"
            },
            {
                "description": "[Interactive] List all available commands",
                "command": "lr"
            }
        ],
        "tldr_source": "official",
        "flags": [
            {
                "flag": "-z",
                "long": null,
                "arg": null,
                "description": "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 undofile argument, the undo file will be written to a file named debugfs-device.e2undo in the directory specified via the E2FSPROGSUNDODIR environment variable. WARNING: The undo file cannot be used to recover from a power or system crash."
            }
        ],
        "examples": [],
        "see_also": [
            {
                "name": "dumpe2fs",
                "section": "8",
                "url": "https://www.chedong.com/phpMan.php/man/dumpe2fs/8/json"
            },
            {
                "name": "tune2fs",
                "section": "8",
                "url": "https://www.chedong.com/phpMan.php/man/tune2fs/8/json"
            },
            {
                "name": "e2fsck",
                "section": "8",
                "url": "https://www.chedong.com/phpMan.php/man/e2fsck/8/json"
            },
            {
                "name": "mke2fs",
                "section": "8",
                "url": "https://www.chedong.com/phpMan.php/man/mke2fs/8/json"
            },
            {
                "name": "ext4",
                "section": "5",
                "url": "https://www.chedong.com/phpMan.php/man/ext4/5/json"
            }
        ],
        "section_outline": [
            {
                "name": "NAME",
                "lines": 2,
                "subsections": []
            },
            {
                "name": "SYNOPSIS",
                "lines": 3,
                "subsections": []
            },
            {
                "name": "DESCRIPTION",
                "lines": 5,
                "subsections": []
            },
            {
                "name": "OPTIONS",
                "lines": 49,
                "subsections": [
                    {
                        "name": "-z _",
                        "lines": 8,
                        "flag": "-z"
                    }
                ]
            },
            {
                "name": "SPECIFYING FILES",
                "lines": 8,
                "subsections": []
            },
            {
                "name": "COMMANDS",
                "lines": 68,
                "subsections": [
                    {
                        "name": "dump_unused",
                        "lines": 92
                    },
                    {
                        "name": "journal_close",
                        "lines": 7
                    },
                    {
                        "name": "journal_run",
                        "lines": 143
                    },
                    {
                        "name": "show_debugfs_params",
                        "lines": 9
                    },
                    {
                        "name": "supported_features",
                        "lines": 42
                    }
                ]
            },
            {
                "name": "ENVIRONMENT VARIABLES",
                "lines": 1,
                "subsections": [
                    {
                        "name": "DEBUGFS_PAGER, PAGER",
                        "lines": 12
                    }
                ]
            },
            {
                "name": "AUTHOR",
                "lines": 2,
                "subsections": []
            },
            {
                "name": "SEE ALSO",
                "lines": 3,
                "subsections": []
            }
        ],
        "sections": {
            "NAME": {
                "content": "debugfs - ext2/ext3/ext4 file system debugger\n",
                "subsections": []
            },
            "SYNOPSIS": {
                "content": "debugfs  [  -DVwcin  ] [ -b blocksize ] [ -s superblock ] [ -f cmdfile ] [ -R request ] [ -d\ndatasourcedevice ] [ -z undofile ] [ device ]\n",
                "subsections": []
            },
            "DESCRIPTION": {
                "content": "The debugfs program is an interactive file system debugger. It can be  used  to  examine  and\nchange the state of an ext2, ext3, or ext4 file system.\n\ndevice is a block device (e.g., /dev/sdXX) or a file containing the file system.\n",
                "subsections": []
            },
            "OPTIONS": {
                "content": "-w     Specifies  that the file system should be opened in read-write mode.  Without this op‐\ntion, the file system is opened in read-only mode.\n\n-n     Disables metadata checksum verification.  This should only be used if you believe  the\nmetadata to be correct despite the complaints of e2fsprogs.\n\n-c     Specifies that the file system should be opened in catastrophic mode, in which the in‐\node  and  group  bitmaps  are not read initially.  This can be useful for file systems\nwith significant corruption, but because of this, catastrophic mode  forces  the  file\nsystem to be opened read-only.\n\n-i     Specifies  that  device  represents an ext2 image file created by the e2image program.\nSince the ext2 image file only contains the superblock, block group descriptor,  block\nand  inode  allocation  bitmaps,  and  the inode table, many debugfs commands will not\nfunction properly.  Warning: no safety checks are in place, and debugfs  may  fail  in\ninteresting  ways  if commands such as ls, dump, etc. are tried without specifying the\ndatasourcedevice using the -d option.  debugfs is a debugging tool.   It  has  rough\nedges!\n\n-d datasourcedevice\nUsed with the -i option, specifies that datasourcedevice should be used when reading\nblocks  not found in the ext2 image file.  This includes data, directory, and indirect\nblocks.\n\n-b blocksize\nForces the use of the given block size (in bytes) for the file system, rather than de‐\ntecting the correct block size automatically.  (This option is rarely  needed;  it  is\nused primarily when the file system is extremely badly damaged/corrupted.)\n\n-s superblock\nCauses  the  file system superblock to be read from the given block number, instead of\nusing the primary superblock (located at an offset of 1024 bytes from the beginning of\nthe file system).  If you specify the -s option, you must also provide  the  blocksize\nof the file system via the -b option.   (This option is rarely needed; it is used pri‐\nmarily when the file system is extremely badly damaged/corrupted.)\n\n-f cmdfile\nCauses  debugfs  to read in commands from cmdfile, and execute them.  When debugfs is\nfinished executing those commands, it will exit.\n\n-D     Causes debugfs to open the device using Direct I/O, bypassing the buffer cache.   Note\nthat  some Linux devices, notably device mapper as of this writing, do not support Di‐\nrect I/O.\n\n-R request\nCauses debugfs to execute the single command request, and then exit.\n\n-V     print the version number of debugfs and exit.\n",
                "subsections": [
                    {
                        "name": "-z _",
                        "content": "Before overwriting a file system block, write the old contents of the block to an undo\nfile.  This undo file can be used with e2undo(8) to restore the old  contents  of  the\nfile system should something go wrong.  If the empty string is passed as the undofile\nargument,  the  undo file will be written to a file named debugfs-device.e2undo in the\ndirectory specified via the E2FSPROGSUNDODIR environment variable.\n\nWARNING: The undo file cannot be used to recover from a power or system crash.\n",
                        "flag": "-z"
                    }
                ]
            },
            "SPECIFYING FILES": {
                "content": "Many debugfs commands take a filespec as an argument to specify an inode  (as  opposed  to  a\npathname) in the file system which is currently opened by debugfs.  The filespec argument may\nbe  specified  in two forms.  The first form is an inode number surrounded by angle brackets,\ne.g., <2>.  The second form is a pathname; if the pathname is prefixed  by  a  forward  slash\n('/'),  then  it  is  interpreted  relative to the root of the file system which is currently\nopened by debugfs.  If not, the pathname is interpreted relative to the current  working  di‐\nrectory as maintained by debugfs.  This may be modified by using the debugfs command cd.\n",
                "subsections": []
            },
            "COMMANDS": {
                "content": "This is a list of the commands which debugfs supports.\n\nblocks filespec\nPrint the blocks used by the inode filespec to stdout.\n\nbmap [ -a ] filespec logicalblock [physicalblock]\nPrint or set the physical block number corresponding to the logical block number logi‐\ncalblock in the inode filespec.  If the -a flag is specified, try to allocate a block\nif necessary.\n\nblockdump '[ -x ] [-f filespec] blocknum\nDump  the file system block given by blocknum in hex and ASCII format to the console.\nIf the -f option is specified, the block number is relative to the start of the  given\nfilespec.   If the -x option is specified, the block is interpreted as an extended at‐\ntribute block and printed to show the structure of extended attribute data structures.\n\ncat filespec\nDump the contents of the inode filespec to stdout.\n\ncd filespec\nChange the current working directory to filespec.\n\nchroot filespec\nChange the root directory to be the directory filespec.\n\nclose [-a]\nClose the currently open file system.  If the -a option is specified,  write  out  any\nchanges  to  the  superblock  and  block  group  descriptors  to all of the backup su‐\nperblocks, not just to the master superblock.\n\nclri filespec\nClear the contents of the inode filespec.\n\ncopyinode sourceinode destinationinode\nCopy the contents of the inode structure in sourceinode and use it to  overwrite  the\ninode structure at destinationinode.\n\ndirsearch filespec filename\nSearch the directory filespec for filename.\n\ndirty [-clean]\nMark the file system as dirty, so that the superblocks will be written on exit.  Addi‐\ntionally, clear the superblock's valid flag, or set it if -clean is specified.\n\ndump [-p] filespec outfile\nDump the contents of the inode filespec to the output file outfile.  If the -p option\nis  given  set the owner, group and permissions information on outfile to match file‐\nspec.\n\ndumpmmp [mmpblock]\nDisplay the multiple-mount protection (mmp) field values.  If mmpblock  is  specified\nthen  verify  and  dump  the MMP values from the given block number, otherwise use the\nsmmpblock field in the superblock to locate and use the existing MMP block.\n\ndxhash [-h hashalg] [-s hashseed] filename\nCalculate the directory hash of filename.  The hash algorithm specified with -h may be\nlegacy, halfmd4, or tea.  The hash seed specified with -s must be in UUID format.\n\ndumpextents [-n] [-l] filespec\nDump the extent tree of the inode filespec.  The -n flag will  cause  dumpextents  to\nonly  display the interior nodes in the extent tree.   The -l flag will cause dumpex‐\ntents to only display the leaf nodes in the extent tree.\n\n(Please note that the length and range of blocks for the last extent  in  an  interior\nnode is an estimate by the extents library functions, and is not stored in file system\ndata  structures.    Hence,  the  values displayed may not necessarily by accurate and\ndoes not indicate a problem or corruption in the file system.)\n",
                "subsections": [
                    {
                        "name": "dump_unused",
                        "content": "Dump unused blocks which contain non-null bytes.\n\neaget [-f outfile]|[-xVC] [-r] filespec attrname\nRetrieve the value of the extended attribute attrname in the file filespec and  write\nit either to stdout or to outfile.\n\nealist filespec\nList the extended attributes associated with the file filespec to standard output.\n\neaset [-f infile] [-r] filespec attrname attrvalue\nSet  the  value of the extended attribute attrname in the file filespec to the string\nvalue attrvalue or read it from infile.\n\nearm filespec attrnames...\nRemove the extended attribute attrname from the file filespec.\n\nexpanddir filespec\nExpand the directory filespec.\n\nfallocate filespec startblock [endblock]\nAllocate and map uninitialized blocks into filespec between logical block  startblock\nand  endblock,  inclusive.  If endblock is not supplied, this function maps until it\nruns out of free disk blocks or the maximum file size is reached.   Existing  mappings\nare left alone.\n\nfeature [fsfeature] [-fsfeature] ...\nSet  or clear various file system features in the superblock.  After setting or clear‐\ning any file system features that were requested, print the current state of the  file\nsystem feature set.\n\nfilefrag [-dvr] filespec\nPrint  the  number  of contiguous extents in filespec.  If filespec is a directory and\nthe -d option is not specified, filefrag will print the number of  contiguous  extents\nfor  each  file  in  the directory.  The -v option will cause filefrag print a tabular\nlisting of the contiguous extents in the file.  The -r option will cause  filefrag  to\ndo a recursive listing of the directory.\n\nfindfreeblock [count [goal]]\nFind  the first count free blocks, starting from goal and allocate it.  Also available\nas ffb.\n\nfindfreeinode [dir [mode]]\nFind a free inode and allocate it.  If present, dir specifies the inode number of  the\ndirectory  which the inode is to be located.  The second optional argument mode speci‐\nfies the permissions of the new inode.  (If the directory bit is set on the mode,  the\nallocation routine will function differently.)  Also available as ffi.\n\nfreeb block [count]\nMark  the  block  number  block  as  not allocated.  If the optional argument count is\npresent, then count blocks starting at block number block will be marked as not  allo‐\ncated.\n\nfreefrag [-c chunkkb]\nReport  free  space fragmentation on the currently open file system.  If the -c option\nis specified then the filefrag command  will  print  how  many  free  chunks  of  size\nchunkkb  can  be found in the file system.  The chunk size must be a power of two and\nbe larger than the file system block size.\n\nfreei filespec [num]\nFree the inode specified by filespec.  If num is specified, also  clear  num-1  inodes\nafter the specified inode.\n\ngetquota quotatype id\nDisplay quota information for given quota type (user, group, or project) and ID.\n\nhelp   Print a list of commands understood by debugfs.\n\nhtreedump filespec\nDump the hash-indexed directory filespec, showing its tree structure.\n\nicheck block ...\nPrint  a  listing of the inodes which use the one or more blocks specified on the com‐\nmand line.\n\ninodedump [-b]|[-e]|[-x] filespec\nPrint the contents of the inode data structure in hex and ASCII format.  The -b option\ncauses the command to only dump the contents of the iblocks  array.   The  -e  option\ncauses  the  command to only dump the contents of the extra inode space, which is used\nto store in-line extended attributes. The -x option causes the command to dump the ex‐\ntra inode space interpreted and extended attributes.  This is  useful  to  debug  cor‐\nrupted inodes containing extended attributes.\n\nimap filespec\nPrint the location of the inode data structure (in the inode table) of the inode file‐\nspec.\n\ninitfilesys device blocksize\nCreate  an ext2 file system on device with device size blocksize.  Note that this does\nnot fully initialize all of the data structures; to do this, use  the  mke2fs(8)  pro‐\ngram.   This is just a call to the low-level library, which sets up the superblock and\nblock descriptors.\n"
                    },
                    {
                        "name": "journal_close",
                        "content": "Close the open journal.\n\njournalopen [-c] [-v ver] [-f extjnl]\nOpens the journal for reading and writing.  Journal checksumming  can  be  enabled  by\nsupplying  -c; checksum formats 2 and 3 can be selected with the -v option.  An exter‐\nnal journal can be loaded from extjnl.\n"
                    },
                    {
                        "name": "journal_run",
                        "content": "Replay all transactions in the open journal.\n\njournalwrite [-b blocks] [-r revoke] [-c] file\nWrite a transaction to the open journal.  The list of blocks to write should  be  sup‐\nplied  as  a  comma-separated list in blocks; the blocks themselves should be readable\nfrom file.  A list of blocks to revoke can be supplied as a  comma-separated  list  in\nrevoke.   By  default,  a commit record is written at the end; the -c switch writes an\nuncommitted transaction.\n\nkillfile filespec\nDeallocate the inode filespec and its blocks.  Note that this does not remove any  di‐\nrectory entries (if any) to this inode.  See the rm(1) command if you wish to unlink a\nfile.\n\nlcd directory\nChange the current working directory of the debugfs process to directory on the native\nfile system.\n\nlistquota quotatype\nDisplay quota information for given quota type (user, group, or project).\n\nln filespec destfile\nCreate  a  link  named destfile which is a hard link to filespec.  Note this does not\nadjust the inode reference counts.\n\nlogdump [-acsOS] [-b block] [-n numtrans ] [-i filespec] [-f journalfile] [outputfile]\nDump the contents of the ext3 journal.  By default, dump the journal inode  as  speci‐\nfied  in  the  superblock.   However, this can be overridden with the -i option, which\ndumps the journal from the internal inode given by filespec.  A regular file  contain‐\ning  journal  data  can be specified using the -f option.  Finally, the -s option uti‐\nlizes the backup information in the superblock to locate the journal.\n\nThe -S option causes logdump to print the contents of the journal superblock.\n\nThe -a option causes the logdump to print  the  contents  of  all  of  the  descriptor\nblocks.   The  -b option causes logdump to print all journal records that refer to the\nspecified block.  The -c option will print out the contents of all of the data  blocks\nselected by the -a and -b options.\n\nThe  -O option causes logdump to display old (checkpointed) journal entries.  This can\nbe used to try to track down journal problems even after  the  journal  has  been  re‐\nplayed.\n\nThe -n option causes logdump to continue past a journal block which is missing a magic\nnumber.   Instead, it will stop only when the entire log is printed or after numtrans\ntransactions.\n\nls [-l] [-c] [-d] [-p] [-r] filespec\nPrint a listing of the files in the directory filespec.  The -c flag causes  directory\nblock  checksums  (if present) to be displayed.  The -d flag will list deleted entries\nin the directory.  The -l flag will list files using a more verbose  format.   The  -p\nflag will list the files in a format which is more easily parsable by scripts, as well\nas  making it more clear when there are spaces or other non-printing characters at the\nend of filenames.  The -r flag will force the printing of the filename, even if it  is\nencrypted.\n\nlistdeletedinodes [limit]\nList  deleted  inodes,  optionally  limited to those deleted within limit seconds ago.\nAlso available as lsdel.\n\nThis command was useful for recovering from accidental file deletions  for  ext2  file\nsystems.   Unfortunately,  it is not useful for this purpose if the files were deleted\nusing ext3 or ext4, since the inode's data blocks are no longer  available  after  the\ninode is released.\n\nmodifyinode filespec\nModify  the  contents of the inode structure in the inode filespec.  Also available as\nmi.\n\nmkdir filespec\nMake a directory.\n\nmknod filespec [p|[[c|b] major minor]]\nCreate a special device file (a named pipe, character or block device).  If a  charac‐\nter  or  block device is to be made, the major and minor device numbers must be speci‐\nfied.\n\nncheck [-c] inodenum ...\nTake the requested list of inode numbers, and print a listing of  pathnames  to  those\ninodes.   The  -c flag will enable checking the file type information in the directory\nentry to make sure it matches the inode's type.\n\nopen [-weficD] [-b blocksize] [-d imagefilename] [-s superblock] [-z undofile] device\nOpen a file system for editing.  The -f flag forces the file system to be opened  even\nif  there  are  some unknown or incompatible file system features which would normally\nprevent the file system from being opened.  The -e flag causes the file system  to  be\nopened  in exclusive mode.  The -b, -c, -d, -i, -s, -w, and -D options behave the same\nas the command-line options to debugfs.\n\npunch filespec startblk [endblk]\nDelete the blocks in the inode ranging from startblk to endblk.  If endblk is omit‐\nted then this command will function as a truncate command; that is, all of the  blocks\nstarting at startblk through to the end of the file will be deallocated.\n\nsymlink filespec target\nMake a symbolic link.\n\npwd    Print the current working directory.\n\nquit   Quit debugfs\n\nrdump directory[...] destination\nRecursively  dump  directory, or multiple directories, and all its contents (including\nregular files, symbolic links, and other  directories)  into  the  named  destination,\nwhich should be an existing directory on the native file system.\n\nrm pathname\nUnlink  pathname.   If  this  causes the inode pointed to by pathname to have no other\nreferences, deallocate the file.  This command functions as the unlink() system call.\n\nrmdir filespec\nRemove the directory filespec.\n\nsetb block [count]\nMark the block number block as allocated.  If the optional argument count is  present,\nthen count blocks starting at block number block will be marked as allocated.\n\nsetblockgroup bgnum field value\nModify  the block group descriptor specified by bgnum so that the block group descrip‐\ntor field field has value value.  Also available as setbg.\n\nsetcurrenttime time\nSet current time in seconds since Unix epoch to use when setting file system fields.\n\nseti filespec [num]\nMark inode filespec as in use in the inode bitmap.  If  num  is  specified,  also  set\nnum-1 inodes after the specified inode.\n\nsetinodefield filespec field value\nModify  the inode specified by filespec so that the inode field field has value value.\nThe list of valid inode fields which can be set via this command can be  displayed  by\nusing the command: setinodefield -l Also available as sif.\n\nsetmmpvalue field value\nModify  the multiple-mount protection (MMP) data so that the MMP field field has value\nvalue.  The list of valid MMP fields which can be set via this  command  can  be  dis‐\nplayed by using the command: setmmpvalue -l Also available as smmp.\n\nsetsupervalue field value\nSet  the  superblock  field field to value.  The list of valid superblock fields which\ncan be set via this command can be displayed by using the command: setsupervalue  -l\nAlso available as ssv.\n"
                    },
                    {
                        "name": "show_debugfs_params",
                        "content": "Display debugfs parameters such as information about currently opened file system.\n\nshowsuperstats [-h]\nList  the contents of the super block and the block group descriptors.  If the -h flag\nis given, only print out the superblock contents. Also available as stats.\n\nstat filespec\nDisplay the contents of the inode structure of the inode filespec.\n"
                    },
                    {
                        "name": "supported_features",
                        "content": "Display file system features supported by this version of debugfs.\n\ntestb block [count]\nTest if the block number block is marked as allocated in the block bitmap.  If the op‐\ntional argument count is present, then count blocks starting  at  block  number  block\nwill be tested.\n\ntesti filespec\nTest if the inode filespec is marked as allocated in the inode bitmap.\n\nundel <inodenumber> [pathname]\nUndelete  the  specified  inode number (which must be surrounded by angle brackets) so\nthat it and its blocks are marked in use, and optionally link the recovered  inode  to\nthe specified pathname.  The e2fsck command should always be run after using the undel\ncommand to recover deleted files.\n\nNote  that if you are recovering a large number of deleted files, linking the inode to\na directory may require the directory to be expanded, which  could  allocate  a  block\nthat  had  been  used  by one of the yet-to-be-undeleted files.  So it is safer to un‐\ndelete all of the inodes without specifying a destination pathname, and then in a sep‐\narate pass, use the debugfs link command to link the inode to  the  destination  path‐\nname,  or  use e2fsck to check the file system and link all of the recovered inodes to\nthe lost+found directory.\n\nunlink pathname\nRemove the link specified by pathname to an inode.  Note this does not adjust the  in‐\node reference counts.\n\nwrite sourcefile outfile\nCopy  the  contents  of sourcefile into a newly-created file in the file system named\noutfile.\n\nzapblock [-f filespec] [-o offset] [-l length] [-p pattern] blocknum\nOverwrite the block specified by blocknum with zero (NUL) bytes, or if  -p  is  given\nuse  the  byte specified by pattern.  If -f is given then blocknum is relative to the\nstart of the file given by filespec.  The -o and -l options limit the range  of  bytes\nto zap to the specified offset and length relative to the start of the block.\n\nzapblock [-f filespec] [-b bit] blocknum\nBit-flip portions of the physical blocknum.  If -f is given, then blocknum is a log‐\nical block relative to the start of filespec.\n"
                    }
                ]
            },
            "ENVIRONMENT VARIABLES": {
                "content": "",
                "subsections": [
                    {
                        "name": "DEBUGFS_PAGER, PAGER",
                        "content": "The  debugfs program always pipes the output of the some commands through a pager pro‐\ngram.  These commands include: showsuperstats (stats), listdirectory (ls), showin‐\nodeinfo (stat), listdeletedinodes (lsdel), and htreedump.  The specific pager  can\nexplicitly  specified by the DEBUGFSPAGER environment variable, and if it is not set,\nby the PAGER environment variable.\n\nNote that since a pager is always used, the less(1) pager is not  particularly  appro‐\npriate,  since  it  clears  the screen before displaying the output of the command and\nclears the output the screen when the pager is exited.  Many users prefer to  use  the\nless(1)  pager  for most purposes, which is why the DEBUGFSPAGER environment variable\nis available to override the more general PAGER environment variable.\n"
                    }
                ]
            },
            "AUTHOR": {
                "content": "debugfs was written by Theodore Ts'o <tytso@mit.edu>.\n",
                "subsections": []
            },
            "SEE ALSO": {
                "content": "dumpe2fs(8), tune2fs(8), e2fsck(8), mke2fs(8), ext4(5)\n\nE2fsprogs version 1.47.0                    February 2023                                 DEBUGFS(8)",
                "subsections": []
            }
        }
    }
}