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
350 Print the location of the inode data structure (in the inode table)
354 .BI init_filesys " device blocksize"
355 Create an ext2 file system on
359 Note that this does not fully initialize all of the data structures;
362 program. This is just a call to the low-level library, which sets up
363 the superblock and block descriptors.
365 .BI kill_file " filespec"
368 and its blocks. Note that this does not remove any directory
369 entries (if any) to this inode. See the
371 command if you wish to unlink a file.
374 Change the current working directory of the
378 on the native filesystem.
380 .BI ln " filespec dest_file"
383 which is a hard link to
385 Note this does not adjust the inode reference counts.
387 .BI logdump " [-acs] [-b block] [-i filespec] [-f journal_file] [output_file]"
388 Dump the contents of the ext3 journal. By default, dump the journal inode as
389 specified in the superblock. However, this can be overridden with the
391 option, which dumps the journal from the internal inode given by
393 A regular file containing journal data can be specified using the
397 option utilizes the backup information in the superblock to locate the
404 program to print the contents of all of the descriptor blocks.
409 to print all journal records that are refer to the specified block.
412 option will print out the contents of all of the data blocks selected by
419 .BI ls " [-d] [-l] [-p] filespec"
420 Print a listing of the files in the directory
424 flag will list deleted entries in the directory.
427 flag will list files using a more verbose format.
430 flag will list the files in a format which is more easily parsable by
431 scripts, as well as making it more clear when there are spaces or other
432 non-printing characters at the end of filenames.
434 .BI list_deleted_inodes " [limit]"
435 List deleted inodes, optionally limited to those deleted within
437 seconds ago. Also available as
440 This command was useful for recovering from accidental file deletions
441 for ext2 file systems. Unfortunately, it is not useful for this purpose
442 if the files were deleted using ext3 or ext4, since the inode's
443 data blocks are no longer available after the inode is released.
445 .BI modify_inode " filespec"
446 Modify the contents of the inode structure in the inode
451 .BI mkdir " filespec"
454 .BI mknod " filespec [p|[[c|b] major minor]]"
455 Create a special device file (a named pipe, character or block device).
456 If a character or block device is to be made, the
460 device numbers must be specified.
462 .BI ncheck " [-c] inode_num ..."
463 Take the requested list of inode numbers, and print a listing of pathnames
466 flag will enable checking the file type information in the directory
467 entry to make sure it matches the inode's type.
469 .BI open " [-weficD] [-b blocksize] [-s superblock] device"
470 Open a filesystem for editing. The
472 flag forces the filesystem to be opened even if there are some unknown
473 or incompatible filesystem features which would normally
474 prevent the filesystem from being opened. The
476 flag causes the filesystem to be opened in exclusive mode. The
477 .IR -b ", " -c ", " -i ", " -s ", " -w ", and " -D
478 options behave the same as the command-line options to
481 .BI punch " filespec start_blk [end_blk]"
482 Delete the blocks in the inode ranging from
488 is omitted then this command will function as a truncate command; that
489 is, all of the blocks starting at
491 through to the end of the file will be deallocated.
493 .BI symlink " filespec target"
494 Make a symbolic link.
497 Print the current working directory.
503 .BI rdump " directory destination"
506 and all its contents (including regular files, symbolic links, and other
507 directories) into the named
509 which should be an existing directory on the native filesystem.
514 If this causes the inode pointed to by
516 to have no other references, deallocate the file. This command functions
517 as the unlink() system call.
520 .BI rmdir " filespec"
524 .BI setb " block [count]"
525 Mark the block number
528 If the optional argument
532 blocks starting at block number
534 will be marked as allocated.
536 .BI set_block_group " bgnum field value"
537 Modify the block group descriptor specified by
539 so that the block group descriptor field
546 .BI seti " filespec [num]"
549 as in use in the inode bitmap. If
551 is specified, also set num-1 inodes after the specified inode.
553 .BI set_inode_field " filespec field value"
554 Modify the inode specified by
556 so that the inode field
560 The list of valid inode fields which can be set via this command
561 can be displayed by using the command:
562 .B set_inode_field -l
566 .BI set_mmp_value " field value"
567 Modify the multiple-mount protection (MMP) data so that the MMP field
571 The list of valid MMP fields which can be set via this command
572 can be displayed by using the command:
577 .BI set_super_value " field value"
578 Set the superblock field
582 The list of valid superblock fields which can be set via this command
583 can be displayed by using the command:
584 .B set_super_value -l
588 .BI show_super_stats " [-h]"
589 List the contents of the super block and the block group descriptors. If the
591 flag is given, only print out the superblock contents. Also available as
595 Display the contents of the inode structure of the inode
598 .BI testb " block [count]"
599 Test if the block number
601 is marked as allocated in the block bitmap.
602 If the optional argument
606 blocks starting at block number
610 .BI testi " filespec"
613 is marked as allocated in the inode bitmap.
615 .BI undel " <inode_number> [pathname]"
616 Undelete the specified inode number (which must be surrounded by angle
617 brackets) so that it and its blocks are marked in use, and optionally
618 link the recovered inode to the specified pathname. The
620 command should always be run after using the
622 command to recover deleted files.
624 Note that if you are recovering a large number of deleted files, linking
625 the inode to a directory may require the directory to be expanded, which
626 could allocate a block that had been used by one of the
627 yet-to-be-undeleted files. So it is safer to undelete all of the
628 inodes without specifying a destination pathname, and then in a separate
629 pass, use the debugfs
631 command to link the inode to the destination pathname, or use
633 to check the filesystem and link all of the recovered inodes to the
634 lost+found directory.
636 .BI unlink " pathname"
637 Remove the link specified by
639 to an inode. Note this does not adjust the inode reference counts.
641 .BI write " source_file out_file"
644 into a newly-created file in the filesystem named
647 .BI zap_block " [-f filespec] [-o offset] [-l length] [-p pattern] block_num"
649 Overwrite the block specified by
651 with zero (NUL) bytes, or if
653 is given use the byte specified by
659 is relative to the start of the file given by
665 options limit the range of bytes to zap to the specified
669 relative to the start of the block.
671 .BI zap_block " [-f filespec] [-b bit] block_num"
672 Bit-flip portions of the physical
678 is a logical block relative to the start of
680 .SH ENVIRONMENT VARIABLES
682 .B DEBUGFS_PAGER, PAGER
685 program always pipes the output of the some commands through a
686 pager program. These commands include:
687 .IR show_super_stats " (" stats ),
688 .IR list_directory " (" ls ),
689 .IR show_inode_info " (" stat ),
690 .IR list_deleted_inodes " (" lsdel ),
693 The specific pager can explicitly specified by the
695 environment variable, and if it is not set, by the
697 environment variable.
699 Note that since a pager is always used, the
701 pager is not particularly appropriate, since it clears the screen before
702 displaying the output of the command and clears the output the screen
703 when the pager is exited. Many users prefer to use the
705 pager for most purposes, which is why the
707 environment variable is available to override the more general
709 environment variable.
712 was written by Theodore Ts'o <tytso@mit.edu>.