2 .\" Copyright 1993, 1994, 1995 by Theodore Ts'o. All Rights Reserved.
3 .\" This file may be copied under the terms of the GNU Public License.
5 .TH DEBUGFS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
7 debugfs \- ext2/ext3/ext4 file system debugger
39 program is an interactive file system debugger. It can be used to
40 examine and change the state of an ext2, ext3, or ext4 file system.
43 is the special file corresponding to the device containing the
44 file system (e.g /dev/hdXX).
48 Specifies that the file system should be opened in read-write mode.
49 Without this option, the file system is opened in read-only mode.
52 Specifies that the file system should be opened in catastrophic mode, in
53 which the inode and group bitmaps are not read initially. This can be
54 useful for filesystems with significant corruption, but because of this,
55 catastrophic mode forces the filesystem to be opened read-only.
60 represents an ext2 image file created by the
62 program. Since the ext2 image file only contains the superblock, block
63 group descriptor, block and inode allocation bitmaps, and
66 commands will not function properly.
68 no safety checks are in place, and
70 may fail in interesting ways if commands such as
72 etc. are tried without specifying the
78 is a debugging tool. It has rough edges!
80 .I -d data_source_device
83 option, specifies that
85 should be used when reading blocks not found in the ext2 image file.
86 This includes data, directory, and indirect blocks.
89 Forces the use of the given block size for the file system, rather than
90 detecting the correct block size as normal.
93 Causes the file system superblock to be read from the given block
94 number, instead of using the primary superblock (located at an offset of
95 1024 bytes from the beginning of the filesystem). If you specify the
97 option, you must also provide the blocksize of the filesystem via the
104 to read in commands from
106 and execute them. When
108 is finished executing those commands, it will exit.
113 to open the device using Direct I/O, bypassing the buffer cache. Note
114 that some Linux devices, notably device mapper as of this writing, do
115 not support Direct I/O.
120 to execute the single command
125 print the version number of
133 as an argument to specify an inode (as opposed to a pathname)
134 in the filesystem which is currently opened by
138 argument may be specified in two forms. The first form is an inode
139 number surrounded by angle brackets, e.g.,
141 The second form is a pathname; if the pathname is prefixed by a forward slash
142 ('/'), then it is interpreted relative to the root of the filesystem
143 which is currently opened by
145 If not, the pathname is
146 interpreted relative to the current working directory as maintained by
148 This may be modified by using the
156 This is a list of the commands which
160 .BI blocks " filespace"
161 Print the blocks used by the inode
165 .BI bmap " filespec logical_block"
166 Print the physical block number corresponding to the logical block number
171 .BI block_dump " [-f filespec] block_num"
172 Dump the filesystem block given by
174 in hex and ASCII format to the console. If the
176 option is specified, the block number is relative to the start of the given
180 Dump the contents of the inode
185 Change the current working directory to
188 .BI chroot " filespec"
189 Change the root directory to be the directory
193 Close the currently open file system. If the
195 option is specified, write out any changes to the superblock and block
196 group descriptors to all of the backup superblocks, not just to the
200 Clear the contents of the inode
203 .BI dirsearch " filespec filename"
210 Mark the filesystem as dirty, so that the superblocks will be written on exit.
212 .BI dump " [-p] filespec out_file"
213 Dump the contents of the inode
219 option is given set the owner, group and permissions information on
225 Display the multiple-mount protection (mmp) field values.
227 .BI dx_hash " [-h hash_alg] [-s hash_seed] filename"
228 Calculate the directory hash of
230 The hash algorithm specified with
233 .BR legacy , " half_md4" ", or " tea .
234 The hash seed specified with
236 must be in UUID format.
238 .BI dump_extents " [-n] [-l] filespec"
239 Dump the the extent tree of the inode
245 to only display the interior nodes in the extent tree. The
249 to only display the leaf nodes in the extent tree.
251 (Please note that the length and range of blocks for the last extent in
252 an interior node is an estimate by the extents library functions, and is
253 not stored in filesystem data structures. Hence, the values displayed
254 may not necessarily by accurate and does not indicate a problem or
255 corruption in the file system.)
257 .BI expand_dir " filespec"
261 .BI feature " [fs_feature] [-fs_feature] ..."
262 Set or clear various filesystem features in the superblock. After setting
263 or clearing any filesystem features that were requested, print the current
264 state of the filesystem feature set.
266 .BI filefrag " [-dvr] filespec"
267 Print the number of contiguous extents in
271 is a directory and the
273 option is not specified,
275 will print the number of contiguous extents for each file in
280 print a tabular listing of the contiguous extents in the
285 to do a recursive listing of the directory.
287 .BI find_free_block " [count [goal]]"
290 free blocks, starting from
292 and allocate it. Also available as
295 .BI find_free_inode " [dir [mode]]"
296 Find a free inode and allocate it. If present,
298 specifies the inode number of the directory
299 which the inode is to be located. The second
302 specifies the permissions of the new inode. (If the directory bit is set
303 on the mode, the allocation routine will function differently.) Also
307 .BI freeb " block [count]"
308 Mark the block number
311 If the optional argument
315 blocks starting at block number
317 will be marked as not allocated.
319 .BI freefrag " [-c chunk_kb]"
320 Report free space fragmentation on the currently open file system.
323 option is specified then the filefrag command will print how many free
326 can be found in the file system. The chunk size must be a power of two
327 and be larger than the file system block size.
329 .BI freei " filespec [num]"
330 Free the inode specified by
334 is specified, also clear num-1 inodes after the specified inode.
337 Print a list of commands understood by
340 .BI htree_dump " filespec"
341 Dump the hash-indexed directory
343 showing its tree structure.
345 .BI icheck " block ..."
346 Print a listing of the inodes which use the one or more blocks specified
349 .BI inode_dump " filespec"
350 Print the contents of the inode data structure in hex and ASCII format.
353 Print the location of the inode data structure (in the inode table)
357 .BI init_filesys " device blocksize"
358 Create an ext2 file system on
362 Note that this does not fully initialize all of the data structures;
365 program. This is just a call to the low-level library, which sets up
366 the superblock and block descriptors.
368 .BI kill_file " filespec"
371 and its blocks. Note that this does not remove any directory
372 entries (if any) to this inode. See the
374 command if you wish to unlink a file.
377 Change the current working directory of the
381 on the native filesystem.
383 .BI ln " filespec dest_file"
386 which is a hard link to
388 Note this does not adjust the inode reference counts.
390 .BI logdump " [-acs] [-b block] [-i filespec] [-f journal_file] [output_file]"
391 Dump the contents of the ext3 journal. By default, dump the journal inode as
392 specified in the superblock. However, this can be overridden with the
394 option, which dumps the journal from the internal inode given by
396 A regular file containing journal data can be specified using the
400 option utilizes the backup information in the superblock to locate the
407 program to print the contents of all of the descriptor blocks.
412 to print all journal records that are refer to the specified block.
415 option will print out the contents of all of the data blocks selected by
422 .BI ls " [-d] [-l] [-p] filespec"
423 Print a listing of the files in the directory
427 flag will list deleted entries in the directory.
430 flag will list files using a more verbose format.
433 flag will list the files in a format which is more easily parsable by
434 scripts, as well as making it more clear when there are spaces or other
435 non-printing characters at the end of filenames.
437 .BI list_deleted_inodes " [limit]"
438 List deleted inodes, optionally limited to those deleted within
440 seconds ago. Also available as
443 This command was useful for recovering from accidental file deletions
444 for ext2 file systems. Unfortunately, it is not useful for this purpose
445 if the files were deleted using ext3 or ext4, since the inode's
446 data blocks are no longer available after the inode is released.
448 .BI modify_inode " filespec"
449 Modify the contents of the inode structure in the inode
454 .BI mkdir " filespec"
457 .BI mknod " filespec [p|[[c|b] major minor]]"
458 Create a special device file (a named pipe, character or block device).
459 If a character or block device is to be made, the
463 device numbers must be specified.
465 .BI ncheck " [-c] inode_num ..."
466 Take the requested list of inode numbers, and print a listing of pathnames
469 flag will enable checking the file type information in the directory
470 entry to make sure it matches the inode's type.
472 .BI open " [-weficD] [-b blocksize] [-s superblock] device"
473 Open a filesystem for editing. The
475 flag forces the filesystem to be opened even if there are some unknown
476 or incompatible filesystem features which would normally
477 prevent the filesystem from being opened. The
479 flag causes the filesystem to be opened in exclusive mode. The
480 .IR -b ", " -c ", " -i ", " -s ", " -w ", and " -D
481 options behave the same as the command-line options to
484 .BI punch " filespec start_blk [end_blk]"
485 Delete the blocks in the inode ranging from
491 is omitted then this command will function as a truncate command; that
492 is, all of the blocks starting at
494 through to the end of the file will be deallocated.
496 .BI symlink " filespec target"
497 Make a symbolic link.
500 Print the current working directory.
506 .BI rdump " directory destination"
509 and all its contents (including regular files, symbolic links, and other
510 directories) into the named
512 which should be an existing directory on the native filesystem.
517 If this causes the inode pointed to by
519 to have no other references, deallocate the file. This command functions
520 as the unlink() system call.
523 .BI rmdir " filespec"
527 .BI setb " block [count]"
528 Mark the block number
531 If the optional argument
535 blocks starting at block number
537 will be marked as allocated.
539 .BI set_block_group " bgnum field value"
540 Modify the block group descriptor specified by
542 so that the block group descriptor field
549 .BI seti " filespec [num]"
552 as in use in the inode bitmap. If
554 is specified, also set num-1 inodes after the specified inode.
556 .BI set_inode_field " filespec field value"
557 Modify the inode specified by
559 so that the inode field
563 The list of valid inode fields which can be set via this command
564 can be displayed by using the command:
565 .B set_inode_field -l
569 .BI set_mmp_value " field value"
570 Modify the multiple-mount protection (MMP) data so that the MMP field
574 The list of valid MMP fields which can be set via this command
575 can be displayed by using the command:
580 .BI set_super_value " field value"
581 Set the superblock field
585 The list of valid superblock fields which can be set via this command
586 can be displayed by using the command:
587 .B set_super_value -l
591 .BI show_super_stats " [-h]"
592 List the contents of the super block and the block group descriptors. If the
594 flag is given, only print out the superblock contents. Also available as
598 Display the contents of the inode structure of the inode
601 .BI testb " block [count]"
602 Test if the block number
604 is marked as allocated in the block bitmap.
605 If the optional argument
609 blocks starting at block number
613 .BI testi " filespec"
616 is marked as allocated in the inode bitmap.
618 .BI undel " <inode_number> [pathname]"
619 Undelete the specified inode number (which must be surrounded by angle
620 brackets) so that it and its blocks are marked in use, and optionally
621 link the recovered inode to the specified pathname. The
623 command should always be run after using the
625 command to recover deleted files.
627 Note that if you are recovering a large number of deleted files, linking
628 the inode to a directory may require the directory to be expanded, which
629 could allocate a block that had been used by one of the
630 yet-to-be-undeleted files. So it is safer to undelete all of the
631 inodes without specifying a destination pathname, and then in a separate
632 pass, use the debugfs
634 command to link the inode to the destination pathname, or use
636 to check the filesystem and link all of the recovered inodes to the
637 lost+found directory.
639 .BI unlink " pathname"
640 Remove the link specified by
642 to an inode. Note this does not adjust the inode reference counts.
644 .BI write " source_file out_file"
647 into a newly-created file in the filesystem named
650 .BI zap_block " [-f filespec] [-o offset] [-l length] [-p pattern] block_num"
652 Overwrite the block specified by
654 with zero (NUL) bytes, or if
656 is given use the byte specified by
662 is relative to the start of the file given by
668 options limit the range of bytes to zap to the specified
672 relative to the start of the block.
674 .BI zap_block " [-f filespec] [-b bit] block_num"
675 Bit-flip portions of the physical
681 is a logical block relative to the start of
683 .SH ENVIRONMENT VARIABLES
685 .B DEBUGFS_PAGER, PAGER
688 program always pipes the output of the some commands through a
689 pager program. These commands include:
690 .IR show_super_stats " (" stats ),
691 .IR list_directory " (" ls ),
692 .IR show_inode_info " (" stat ),
693 .IR list_deleted_inodes " (" lsdel ),
696 The specific pager can explicitly specified by the
698 environment variable, and if it is not set, by the
700 environment variable.
702 Note that since a pager is always used, the
704 pager is not particularly appropriate, since it clears the screen before
705 displaying the output of the command and clears the output the screen
706 when the pager is exited. Many users prefer to use the
708 pager for most purposes, which is why the
710 environment variable is available to override the more general
712 environment variable.
715 was written by Theodore Ts'o <tytso@mit.edu>.