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 Disables metadata checksum verification. This should only be used if
53 you believe the metadata to be correct despite the complaints of
57 Specifies that the file system should be opened in catastrophic mode, in
58 which the inode and group bitmaps are not read initially. This can be
59 useful for filesystems with significant corruption, but because of this,
60 catastrophic mode forces the filesystem to be opened read-only.
65 represents an ext2 image file created by the
67 program. Since the ext2 image file only contains the superblock, block
68 group descriptor, block and inode allocation bitmaps, and
71 commands will not function properly.
73 no safety checks are in place, and
75 may fail in interesting ways if commands such as
77 etc. are tried without specifying the
83 is a debugging tool. It has rough edges!
85 .I -d data_source_device
88 option, specifies that
90 should be used when reading blocks not found in the ext2 image file.
91 This includes data, directory, and indirect blocks.
94 Forces the use of the given block size for the file system, rather than
95 detecting the correct block size as normal.
98 Causes the file system superblock to be read from the given block
99 number, instead of using the primary superblock (located at an offset of
100 1024 bytes from the beginning of the filesystem). If you specify the
102 option, you must also provide the blocksize of the filesystem via the
109 to read in commands from
111 and execute them. When
113 is finished executing those commands, it will exit.
118 to open the device using Direct I/O, bypassing the buffer cache. Note
119 that some Linux devices, notably device mapper as of this writing, do
120 not support Direct I/O.
125 to execute the single command
130 print the version number of
138 as an argument to specify an inode (as opposed to a pathname)
139 in the filesystem which is currently opened by
143 argument may be specified in two forms. The first form is an inode
144 number surrounded by angle brackets, e.g.,
146 The second form is a pathname; if the pathname is prefixed by a forward slash
147 ('/'), then it is interpreted relative to the root of the filesystem
148 which is currently opened by
150 If not, the pathname is
151 interpreted relative to the current working directory as maintained by
153 This may be modified by using the
161 This is a list of the commands which
165 .BI blocks " filespace"
166 Print the blocks used by the inode
170 .BI bmap " filespec logical_block"
171 Print the physical block number corresponding to the logical block number
176 .BI block_dump " [-f filespec] block_num"
177 Dump the filesystem block given by
179 in hex and ASCII format to the console. If the
181 option is specified, the block number is relative to the start of the given
185 Dump the contents of the inode
190 Change the current working directory to
193 .BI chroot " filespec"
194 Change the root directory to be the directory
198 Close the currently open file system. If the
200 option is specified, write out any changes to the superblock and block
201 group descriptors to all of the backup superblocks, not just to the
205 Clear the contents of the inode
208 .BI dirsearch " filespec filename"
215 Mark the filesystem as dirty, so that the superblocks will be written on exit.
217 .BI dump " [-p] filespec out_file"
218 Dump the contents of the inode
224 option is given set the owner, group and permissions information on
230 Display the multiple-mount protection (mmp) field values.
232 .BI dx_hash " [-h hash_alg] [-s hash_seed] filename"
233 Calculate the directory hash of
235 The hash algorithm specified with
238 .BR legacy , " half_md4" ", or " tea .
239 The hash seed specified with
241 must be in UUID format.
243 .BI dump_extents " [-n] [-l] filespec"
244 Dump the the extent tree of the inode
250 to only display the interior nodes in the extent tree. The
254 to only display the leaf nodes in the extent tree.
256 (Please note that the length and range of blocks for the last extent in
257 an interior node is an estimate by the extents library functions, and is
258 not stored in filesystem data structures. Hence, the values displayed
259 may not necessarily by accurate and does not indicate a problem or
260 corruption in the file system.)
262 .BI expand_dir " filespec"
266 .BI feature " [fs_feature] [-fs_feature] ..."
267 Set or clear various filesystem features in the superblock. After setting
268 or clearing any filesystem features that were requested, print the current
269 state of the filesystem feature set.
271 .BI filefrag " [-dvr] filespec"
272 Print the number of contiguous extents in
276 is a directory and the
278 option is not specified,
280 will print the number of contiguous extents for each file in
285 print a tabular listing of the contiguous extents in the
290 to do a recursive listing of the directory.
292 .BI find_free_block " [count [goal]]"
295 free blocks, starting from
297 and allocate it. Also available as
300 .BI find_free_inode " [dir [mode]]"
301 Find a free inode and allocate it. If present,
303 specifies the inode number of the directory
304 which the inode is to be located. The second
307 specifies the permissions of the new inode. (If the directory bit is set
308 on the mode, the allocation routine will function differently.) Also
312 .BI freeb " block [count]"
313 Mark the block number
316 If the optional argument
320 blocks starting at block number
322 will be marked as not allocated.
324 .BI freefrag " [-c chunk_kb]"
325 Report free space fragmentation on the currently open file system.
328 option is specified then the filefrag command will print how many free
331 can be found in the file system. The chunk size must be a power of two
332 and be larger than the file system block size.
334 .BI freei " filespec [num]"
335 Free the inode specified by
339 is specified, also clear num-1 inodes after the specified inode.
342 Print a list of commands understood by
345 .BI htree_dump " filespec"
346 Dump the hash-indexed directory
348 showing its tree structure.
350 .BI icheck " block ..."
351 Print a listing of the inodes which use the one or more blocks specified
354 .BI inode_dump " filespec"
355 Print the contents of the inode data structure in hex and ASCII format.
358 Print the location of the inode data structure (in the inode table)
362 .BI init_filesys " device blocksize"
363 Create an ext2 file system on
367 Note that this does not fully initialize all of the data structures;
370 program. This is just a call to the low-level library, which sets up
371 the superblock and block descriptors.
373 .BI kill_file " filespec"
376 and its blocks. Note that this does not remove any directory
377 entries (if any) to this inode. See the
379 command if you wish to unlink a file.
382 Change the current working directory of the
386 on the native filesystem.
388 .BI ln " filespec dest_file"
391 which is a hard link to
393 Note this does not adjust the inode reference counts.
395 .BI logdump " [-acsO] [-b block] [-i filespec] [-f journal_file] [output_file]"
396 Dump the contents of the ext3 journal. By default, dump the journal inode as
397 specified in the superblock. However, this can be overridden with the
399 option, which dumps the journal from the internal inode given by
401 A regular file containing journal data can be specified using the
405 option utilizes the backup information in the superblock to locate the
412 program to print the contents of all of the descriptor blocks.
417 to print all journal records that are refer to the specified block.
420 option will print out the contents of all of the data blocks selected by
429 option causes logdump to display old (checkpointed) journal entries.
430 This can be used to try to track down journal problems even after the
431 journal has been replayed.
433 .BI ls " [-l] [-c] [-d] [-p] filespec"
434 Print a listing of the files in the directory
438 flag causes directory block checksums (if present) to be displayed.
441 flag will list deleted entries in the directory.
444 flag will list files using a more verbose format.
447 flag will list the files in a format which is more easily parsable by
448 scripts, as well as making it more clear when there are spaces or other
449 non-printing characters at the end of filenames.
451 .BI list_deleted_inodes " [limit]"
452 List deleted inodes, optionally limited to those deleted within
454 seconds ago. Also available as
457 This command was useful for recovering from accidental file deletions
458 for ext2 file systems. Unfortunately, it is not useful for this purpose
459 if the files were deleted using ext3 or ext4, since the inode's
460 data blocks are no longer available after the inode is released.
462 .BI modify_inode " filespec"
463 Modify the contents of the inode structure in the inode
468 .BI mkdir " filespec"
471 .BI mknod " filespec [p|[[c|b] major minor]]"
472 Create a special device file (a named pipe, character or block device).
473 If a character or block device is to be made, the
477 device numbers must be specified.
479 .BI ncheck " [-c] inode_num ..."
480 Take the requested list of inode numbers, and print a listing of pathnames
483 flag will enable checking the file type information in the directory
484 entry to make sure it matches the inode's type.
486 .BI open " [-weficD] [-b blocksize] [-s superblock] device"
487 Open a filesystem for editing. The
489 flag forces the filesystem to be opened even if there are some unknown
490 or incompatible filesystem features which would normally
491 prevent the filesystem from being opened. The
493 flag causes the filesystem to be opened in exclusive mode. The
494 .IR -b ", " -c ", " -i ", " -s ", " -w ", and " -D
495 options behave the same as the command-line options to
498 .BI punch " filespec start_blk [end_blk]"
499 Delete the blocks in the inode ranging from
505 is omitted then this command will function as a truncate command; that
506 is, all of the blocks starting at
508 through to the end of the file will be deallocated.
510 .BI symlink " filespec target"
511 Make a symbolic link.
514 Print the current working directory.
520 .BI rdump " directory destination"
523 and all its contents (including regular files, symbolic links, and other
524 directories) into the named
526 which should be an existing directory on the native filesystem.
531 If this causes the inode pointed to by
533 to have no other references, deallocate the file. This command functions
534 as the unlink() system call.
537 .BI rmdir " filespec"
541 .BI setb " block [count]"
542 Mark the block number
545 If the optional argument
549 blocks starting at block number
551 will be marked as allocated.
553 .BI set_block_group " bgnum field value"
554 Modify the block group descriptor specified by
556 so that the block group descriptor field
563 .BI seti " filespec [num]"
566 as in use in the inode bitmap. If
568 is specified, also set num-1 inodes after the specified inode.
570 .BI set_inode_field " filespec field value"
571 Modify the inode specified by
573 so that the inode field
577 The list of valid inode fields which can be set via this command
578 can be displayed by using the command:
579 .B set_inode_field -l
583 .BI set_mmp_value " field value"
584 Modify the multiple-mount protection (MMP) data so that the MMP field
588 The list of valid MMP fields which can be set via this command
589 can be displayed by using the command:
594 .BI set_super_value " field value"
595 Set the superblock field
599 The list of valid superblock fields which can be set via this command
600 can be displayed by using the command:
601 .B set_super_value -l
605 .BI show_super_stats " [-h]"
606 List the contents of the super block and the block group descriptors. If the
608 flag is given, only print out the superblock contents. Also available as
612 Display the contents of the inode structure of the inode
615 .BI testb " block [count]"
616 Test if the block number
618 is marked as allocated in the block bitmap.
619 If the optional argument
623 blocks starting at block number
627 .BI testi " filespec"
630 is marked as allocated in the inode bitmap.
632 .BI undel " <inode_number> [pathname]"
633 Undelete the specified inode number (which must be surrounded by angle
634 brackets) so that it and its blocks are marked in use, and optionally
635 link the recovered inode to the specified pathname. The
637 command should always be run after using the
639 command to recover deleted files.
641 Note that if you are recovering a large number of deleted files, linking
642 the inode to a directory may require the directory to be expanded, which
643 could allocate a block that had been used by one of the
644 yet-to-be-undeleted files. So it is safer to undelete all of the
645 inodes without specifying a destination pathname, and then in a separate
646 pass, use the debugfs
648 command to link the inode to the destination pathname, or use
650 to check the filesystem and link all of the recovered inodes to the
651 lost+found directory.
653 .BI unlink " pathname"
654 Remove the link specified by
656 to an inode. Note this does not adjust the inode reference counts.
658 .BI write " source_file out_file"
661 into a newly-created file in the filesystem named
664 .BI zap_block " [-f filespec] [-o offset] [-l length] [-p pattern] block_num"
666 Overwrite the block specified by
668 with zero (NUL) bytes, or if
670 is given use the byte specified by
676 is relative to the start of the file given by
682 options limit the range of bytes to zap to the specified
686 relative to the start of the block.
688 .BI zap_block " [-f filespec] [-b bit] block_num"
689 Bit-flip portions of the physical
695 is a logical block relative to the start of
697 .SH ENVIRONMENT VARIABLES
699 .B DEBUGFS_PAGER, PAGER
702 program always pipes the output of the some commands through a
703 pager program. These commands include:
704 .IR show_super_stats " (" stats ),
705 .IR list_directory " (" ls ),
706 .IR show_inode_info " (" stat ),
707 .IR list_deleted_inodes " (" lsdel ),
710 The specific pager can explicitly specified by the
712 environment variable, and if it is not set, by the
714 environment variable.
716 Note that since a pager is always used, the
718 pager is not particularly appropriate, since it clears the screen before
719 displaying the output of the command and clears the output the screen
720 when the pager is exited. Many users prefer to use the
722 pager for most purposes, which is why the
724 environment variable is available to override the more general
726 environment variable.
729 was written by Theodore Ts'o <tytso@mit.edu>.