debugfs/debugfs.8.in

   1 .\" -*- nroff -*-
   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.
   4 .\"
   5 .TH DEBUGFS 8 "@E2FSPROGS_MONTH@ @E2FSPROGS_YEAR@" "E2fsprogs version @E2FSPROGS_VERSION@"
   6 .SH NAME
   7 debugfs \- ext2/ext3/ext4 file system debugger
   8 .SH SYNOPSIS
   9 .B debugfs
  10 [
  11 .B \-DVwcin
  12 ]
  13 [
  14 .B \-b
  15 blocksize
  16 ]
  17 [
  18 .B \-s
  19 superblock
  20 ]
  21 [
  22 .B \-f
  23 cmd_file
  24 ]
  25 [
  26 .B \-R
  27 request
  28 ]
  29 [
  30 .B \-d
  31 data_source_device
  32 ]
  33 [
  34 device
  35 ]
  36 .SH DESCRIPTION
  37 The
  38 .B debugfs
  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.
  41 .br
  42 .I device
  43 is the special file corresponding to the device containing the
  44 file system (e.g /dev/hdXX).
  45 .SH OPTIONS
  46 .TP
  47 .I \-w
  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.
  50 .TP
  51 .I \-n
  52 Disables metadata checksum verification.  This should only be used if
  53 you believe the metadata to be correct despite the complaints of
  54 e2fsprogs.
  55 .TP
  56 .I \-c
  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.
  61 .TP
  62 .I \-i
  63 Specifies that
  64 .I device
  65 represents an ext2 image file created by the
  66 .B e2image
  67 program.  Since the ext2 image file only contains the superblock, block
  68 group descriptor, block and inode allocation bitmaps, and
  69 the inode table, many
  70 .B debugfs
  71 commands will not function properly.
  72 .B Warning:
  73 no safety checks are in place, and
  74 .B debugfs
  75 may fail in interesting ways if commands such as
  76 .IR ls ", " dump ", "
  77 etc. are tried without specifying the
  78 .I data_source_device
  79 using the
  80 .I \-d
  81 option.
  82 .B debugfs
  83 is a debugging tool.  It has rough edges!
  84 .TP
  85 .I -d data_source_device
  86 Used with the
  87 .I \-i
  88 option, specifies that
  89 .I data_source_device
  90 should be used when reading blocks not found in the ext2 image file.
  91 This includes data, directory, and indirect blocks.
  92 .TP
  93 .I -b blocksize
  94 Forces the use of the given block size for the file system, rather than
  95 detecting the correct block size as normal.
  96 .TP
  97 .I -s superblock
  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
 101 .I -s
 102 option, you must also provide the blocksize of the filesystem via the
 103 .I -b
 104 option.
 105 .TP
 106 .I -f cmd_file
 107 Causes
 108 .B debugfs
 109 to read in commands from
 110 .IR cmd_file ,
 111 and execute them.  When
 112 .B debugfs
 113 is finished executing those commands, it will exit.
 114 .TP
 115 .I -D
 116 Causes
 117 .B debugfs
 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.
 121 .TP
 122 .I -R request
 123 Causes
 124 .B debugfs
 125 to execute the single command
 126 .IR request ,
 127 and then exit.
 128 .TP
 129 .I -V
 130 print the version number of
 131 .B debugfs
 132 and exit.
 133 .SH SPECIFYING FILES
 134 Many
 135 .B debugfs
 136 commands take a
 137 .I filespec
 138 as an argument to specify an inode (as opposed to a pathname)
 139 in the filesystem which is currently opened by
 140 .BR debugfs .
 141 The
 142 .I filespec
 143 argument may be specified in two forms.  The first form is an inode
 144 number surrounded by angle brackets, e.g.,
 145 .IR <2> .
 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
 149 .BR debugfs .
 150 If not, the pathname is
 151 interpreted relative to the current working directory as maintained by
 152 .BR debugfs .
 153 This may be modified by using the
 154 .B debugfs
 155 command
 156 .IR cd .
 157 .\"
 158 .\"
 159 .\"
 160 .SH COMMANDS
 161 This is a list of the commands which
 162 .B debugfs
 163 supports.
 164 .TP
 165 .BI blocks " filespace"
 166 Print the blocks used by the inode
 167 .I filespec
 168 to stdout.
 169 .TP
 170 .BI bmap " filespec logical_block"
 171 Print the physical block number corresponding to the logical block number
 172 .I logical_block
 173 in the inode
 174 .IR filespec .
 175 .TP
 176 .BI block_dump " [-f filespec] block_num"
 177 Dump the filesystem block given by
 178 .I block_num
 179 in hex and ASCII format to the console.  If the
 180 .I -f
 181 option is specified, the block number is relative to the start of the given
 182 .BR filespec .
 183 .TP
 184 .BI cat " filespec"
 185 Dump the contents of the inode
 186 .I filespec
 187 to stdout.
 188 .TP
 189 .BI cd " filespec"
 190 Change the current working directory to
 191 .IR filespec .
 192 .TP
 193 .BI chroot " filespec"
 194 Change the root directory to be the directory
 195 .IR filespec .
 196 .TP
 197 .BI close " [-a]"
 198 Close the currently open file system.  If the
 199 .I -a
 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
 202 master superblock.
 203 .TP
 204 .BI clri " filespec"
 205 Clear the contents of the inode
 206 .IR filespec .
 207 .TP
 208 .BI dirsearch " filespec filename"
 209 Search the directory
 210 .I filespec
 211 for
 212 .IR filename .
 213 .TP
 214 .B dirty
 215 Mark the filesystem as dirty, so that the superblocks will be written on exit.
 216 .TP
 217 .BI dump " [-p] filespec out_file"
 218 Dump the contents of the inode
 219 .I filespec
 220 to the output file
 221 .IR out_file .
 222 If the
 223 .I -p
 224 option is given set the owner, group and permissions information on
 225 .I out_file
 226 to match
 227 .IR filespec .
 228 .TP
 229 .B dump_mmp
 230 Display the multiple-mount protection (mmp) field values.
 231 .TP
 232 .BI dx_hash " [-h hash_alg] [-s hash_seed] filename"
 233 Calculate the directory hash of
 234 .IR filename .
 235 The hash algorithm specified with
 236 .I -h
 237 may be
 238 .BR legacy , " half_md4" ", or " tea .
 239 The hash seed specified with
 240 .I -s
 241 must be in UUID format.
 242 .TP
 243 .BI dump_extents " [-n] [-l] filespec"
 244 Dump the the extent tree of the inode
 245 .IR filespec .
 246 The
 247 .I -n
 248 flag will cause
 249 .B dump_extents
 250 to only display the interior nodes in the extent tree.   The
 251 .I -l
 252 flag will cause
 253 .B dump_extents
 254 to only display the leaf nodes in the extent tree.
 255 .IP
 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.)
 261 .TP
 262 .BI expand_dir " filespec"
 263 Expand the directory
 264 .IR filespec .
 265 .TP
 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.
 270 .TP
 271 .BI filefrag " [-dvr] filespec"
 272 Print the number of contiguous extents in
 273 .IR filespec .
 274 If
 275 .I filespec
 276 is a directory and the
 277 .I -d
 278 option is not specified,
 279 .I filefrag
 280 will print the number of contiguous extents for each file in
 281 the directory.  The
 282 .I -v
 283 option will cause
 284 .I filefrag
 285 print a tabular listing of the contiguous extents in the
 286 file.  The
 287 .I -r
 288 option will cause
 289 .I filefrag
 290 to do a recursive listing of the directory.
 291 .TP
 292 .BI find_free_block " [count [goal]]"
 293 Find the first
 294 .I count
 295 free blocks, starting from
 296 .I goal
 297 and allocate it.  Also available as
 298 .BR ffb .
 299 .TP
 300 .BI find_free_inode " [dir [mode]]"
 301 Find a free inode and allocate it.  If present,
 302 .I dir
 303 specifies the inode number of the directory
 304 which the inode is to be located.  The second
 305 optional argument
 306 .I mode
 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
 309 available as
 310 .BR ffi .
 311 .TP
 312 .BI freeb " block [count]"
 313 Mark the block number
 314 .I block
 315 as not allocated.
 316 If the optional argument
 317 .I count
 318 is present, then
 319 .I count
 320 blocks starting at block number
 321 .I block
 322 will be marked as not allocated.
 323 .TP
 324 .BI freefrag " [-c chunk_kb]"
 325 Report free space fragmentation on the currently open file system.
 326 If the
 327 .I \-c
 328 option is specified then the filefrag command will print how many free
 329 chunks of size
 330 .I chunk_kb
 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.
 333 .TP
 334 .BI freei " filespec [num]"
 335 Free the inode specified by
 336 .IR filespec .
 337 If
 338 .I num
 339 is specified, also clear num-1 inodes after the specified inode.
 340 .TP
 341 .B help
 342 Print a list of commands understood by
 343 .BR debugfs .
 344 .TP
 345 .BI htree_dump " filespec"
 346 Dump the hash-indexed directory
 347 .IR filespec ,
 348 showing its tree structure.
 349 .TP
 350 .BI icheck " block ..."
 351 Print a listing of the inodes which use the one or more blocks specified
 352 on the command line.
 353 .TP
 354 .BI imap " filespec"
 355 Print the location of the inode data structure (in the inode table)
 356 of the inode
 357 .IR filespec .
 358 .TP
 359 .BI init_filesys " device blocksize"
 360 Create an ext2 file system on
 361 .I device
 362 with device size
 363 .IR blocksize .
 364 Note that this does not fully initialize all of the data structures;
 365 to do this, use the
 366 .BR mke2fs (8)
 367 program.  This is just a call to the low-level library, which sets up
 368 the superblock and block descriptors.
 369 .TP
 370 .BI kill_file " filespec"
 371 Deallocate the inode
 372 .I filespec
 373 and its blocks.  Note that this does not remove any directory
 374 entries (if any) to this inode.  See the
 375 .BR rm (1)
 376 command if you wish to unlink a file.
 377 .TP
 378 .BI lcd " directory"
 379 Change the current working directory of the
 380 .B debugfs
 381 process to
 382 .I directory
 383 on the native filesystem.
 384 .TP
 385 .BI ln " filespec dest_file"
 386 Create a link named
 387 .I dest_file
 388 which is a hard link to
 389 .IR filespec .
 390 Note this does not adjust the inode reference counts.
 391 .TP
 392 .BI logdump " [-acs] [-b block] [-i filespec] [-f journal_file] [output_file]"
 393 Dump the contents of the ext3 journal.  By default, dump the journal inode as
 394 specified in the superblock.  However, this can be overridden with the
 395 .I \-i
 396 option, which dumps the journal from the internal inode given by
 397 .IR filespec .
 398 A regular file containing journal data can be specified using the
 399 .I \-f
 400 option.  Finally, the
 401 .I \-s
 402 option utilizes the backup information in the superblock to locate the
 403 journal.
 404 .IP
 405 The
 406 .I \-a
 407 option causes the
 408 .B logdump
 409 program to print the contents of all of the descriptor blocks.
 410 The
 411 .I \-b
 412 option causes
 413 .B logdump
 414 to print all journal records that are refer to the specified block.
 415 The
 416 .I \-c
 417 option will print out the contents of all of the data blocks selected by
 418 the
 419 .I \-a
 420 and
 421 .I \-b
 422 options.
 423 .TP
 424 .BI ls " [-l] [-c] [-d] [-p] filespec"
 425 Print a listing of the files in the directory
 426 .IR filespec .
 427 The
 428 .I \-c
 429 flag causes directory block checksums (if present) to be displayed.
 430 The
 431 .I \-d
 432 flag will list deleted entries in the directory.
 433 The
 434 .I \-l
 435 flag will list files using a more verbose format.
 436 The
 437 .I \-p
 438 flag will list the files in a format which is more easily parsable by
 439 scripts, as well as making it more clear when there are spaces or other
 440 non-printing characters at the end of filenames.
 441 .TP
 442 .BI list_deleted_inodes " [limit]"
 443 List deleted inodes, optionally limited to those deleted within
 444 .I limit
 445 seconds ago.  Also available as
 446 .BR lsdel .
 447 .IP
 448 This command was useful for recovering from accidental file deletions
 449 for ext2 file systems.  Unfortunately, it is not useful for this purpose
 450 if the files were deleted using ext3 or ext4, since the inode's
 451 data blocks are no longer available after the inode is released.
 452 .TP
 453 .BI modify_inode " filespec"
 454 Modify the contents of the inode structure in the inode
 455 .IR filespec .
 456 Also available as
 457 .BR mi .
 458 .TP
 459 .BI mkdir " filespec"
 460 Make a directory.
 461 .TP
 462 .BI mknod " filespec [p|[[c|b] major minor]]"
 463 Create a special device file (a named pipe, character or block device).
 464 If a character or block device is to be made, the
 465 .I major
 466 and
 467 .I minor
 468 device numbers must be specified.
 469 .TP
 470 .BI ncheck " [-c] inode_num ..."
 471 Take the requested list of inode numbers, and print a listing of pathnames
 472 to those inodes.  The
 473 .I -c
 474 flag will enable checking the file type information in the directory
 475 entry to make sure it matches the inode's type.
 476 .TP
 477 .BI open " [-weficD] [-b blocksize] [-s superblock] device"
 478 Open a filesystem for editing.  The
 479 .I -f
 480 flag forces the filesystem to be opened even if there are some unknown
 481 or incompatible filesystem features which would normally
 482 prevent the filesystem from being opened.  The
 483 .I -e
 484 flag causes the filesystem to be opened in exclusive mode.  The
 485 .IR -b ", " -c ", " -i ", " -s ", " -w ", and " -D
 486 options behave the same as the command-line options to
 487 .BR debugfs .
 488 .TP
 489 .BI punch " filespec start_blk [end_blk]"
 490 Delete the blocks in the inode ranging from
 491 .I start_blk
 492 to
 493 .IR end_blk .
 494 If
 495 .I end_blk
 496 is omitted then this command will function as a truncate command; that
 497 is, all of the blocks starting at
 498 .I start_blk
 499 through to the end of the file will be deallocated.
 500 .TP
 501 .BI symlink " filespec target"
 502 Make a symbolic link.
 503 .TP
 504 .B pwd
 505 Print the current working directory.
 506 .TP
 507 .B quit
 508 Quit
 509 .B debugfs
 510 .TP
 511 .BI rdump " directory destination"
 512 Recursively dump
 513 .I directory
 514 and all its contents (including regular files, symbolic links, and other
 515 directories) into the named
 516 .I destination
 517 which should be an existing directory on the native filesystem.
 518 .TP
 519 .BI rm " pathname"
 520 Unlink
 521 .IR pathname .
 522 If this causes the inode pointed to by
 523 .I pathname
 524 to have no other references, deallocate the file.  This command functions
 525 as the unlink() system call.
 526 .I
 527 .TP
 528 .BI rmdir " filespec"
 529 Remove the directory
 530 .IR filespec .
 531 .TP
 532 .BI setb " block [count]"
 533 Mark the block number
 534 .I block
 535 as allocated.
 536 If the optional argument
 537 .I count
 538 is present, then
 539 .I count
 540 blocks starting at block number
 541 .I block
 542 will be marked as allocated.
 543 .TP
 544 .BI set_block_group " bgnum field value"
 545 Modify the block group descriptor specified by
 546 .I bgnum
 547 so that the block group descriptor field
 548 .I field
 549 has value
 550 .IR value .
 551 Also available as
 552 .BR set_bg .
 553 .TP
 554 .BI seti " filespec [num]"
 555 Mark inode
 556 .I filespec
 557 as in use in the inode bitmap.  If
 558 .I num
 559 is specified, also set num-1 inodes after the specified inode.
 560 .TP
 561 .BI set_inode_field " filespec field value"
 562 Modify the inode specified by
 563 .I filespec
 564 so that the inode field
 565 .I field
 566 has value
 567 .I value.
 568 The list of valid inode fields which can be set via this command
 569 can be displayed by using the command:
 570 .B set_inode_field -l
 571 Also available as
 572 .BR sif .
 573 .TP
 574 .BI set_mmp_value " field value"
 575 Modify the multiple-mount protection (MMP) data so that the MMP field
 576 .I field
 577 has value
 578 .I value.
 579 The list of valid MMP fields which can be set via this command
 580 can be displayed by using the command:
 581 .B set_mmp_value -l
 582 Also available as
 583 .BR smmp .
 584 .TP
 585 .BI set_super_value " field value"
 586 Set the superblock field
 587 .I field
 588 to
 589 .I value.
 590 The list of valid superblock fields which can be set via this command
 591 can be displayed by using the command:
 592 .B set_super_value -l
 593 Also available as
 594 .BR ssv .
 595 .TP
 596 .BI show_super_stats " [-h]"
 597 List the contents of the super block and the block group descriptors.  If the
 598 .I -h
 599 flag is given, only print out the superblock contents. Also available as
 600 .BR stats .
 601 .TP
 602 .BI stat " filespec"
 603 Display the contents of the inode structure of the inode
 604 .IR filespec .
 605 .TP
 606 .BI testb " block [count]"
 607 Test if the block number
 608 .I block
 609 is marked as allocated in the block bitmap.
 610 If the optional argument
 611 .I count
 612 is present, then
 613 .I count
 614 blocks starting at block number
 615 .I block
 616 will be tested.
 617 .TP
 618 .BI testi " filespec"
 619 Test if the inode
 620 .I filespec
 621 is marked as allocated in the inode bitmap.
 622 .TP
 623 .BI undel " <inode_number> [pathname]"
 624 Undelete the specified inode number (which must be surrounded by angle
 625 brackets) so that it and its blocks are marked in use, and optionally
 626 link the recovered inode to the specified pathname.  The
 627 .B e2fsck
 628 command should always be run after using the
 629 .B undel
 630 command to recover deleted files.
 631 .IP
 632 Note that if you are recovering a large number of deleted files, linking
 633 the inode to a directory may require the directory to be expanded, which
 634 could allocate a block that had been used by one of the
 635 yet-to-be-undeleted files.  So it is safer to undelete all of the
 636 inodes without specifying a destination pathname, and then in a separate
 637 pass, use the debugfs
 638 .B link
 639 command to link the inode to the destination pathname, or use
 640 .B e2fsck
 641 to check the filesystem and link all of the recovered inodes to the
 642 lost+found directory.
 643 .TP
 644 .BI unlink " pathname"
 645 Remove the link specified by
 646 .I pathname
 647 to an inode.  Note this does not adjust the inode reference counts.
 648 .TP
 649 .BI write " source_file out_file"
 650 Copy the contents of
 651 .I source_file
 652 into a newly-created file in the filesystem named
 653 .IR out_file .
 654 .TP
 655 .BI zap_block " [-f filespec] [-o offset] [-l length] [-p pattern] block_num"
 656 .TP
 657 Overwrite the block specified by
 658 .I block_num
 659 with zero (NUL) bytes, or if
 660 .I -p
 661 is given use the byte specified by
 662 .IR pattern .
 663 If
 664 .I -f
 665 is given then
 666 .I block_num
 667 is relative to the start of the file given by
 668 .IR filespec .
 669 The
 670 .I -o
 671 and
 672 .I -l
 673 options limit the range of bytes to zap to the specified
 674 .I offset
 675 and
 676 .I length
 677 relative to the start of the block.
 678 .TP
 679 .BI zap_block " [-f filespec] [-b bit] block_num"
 680 Bit-flip portions of the physical
 681 .IR block_num .
 682 If
 683 .I -f
 684 is given, then
 685 .I block_num
 686 is a logical block relative to the start of
 687 .IR filespec .
 688 .SH ENVIRONMENT VARIABLES
 689 .TP
 690 .B DEBUGFS_PAGER, PAGER
 691 The
 692 .B debugfs
 693 program always pipes the output of the some commands through a
 694 pager program.  These commands include:
 695 .IR show_super_stats " (" stats ),
 696 .IR list_directory " (" ls ),
 697 .IR show_inode_info " (" stat ),
 698 .IR list_deleted_inodes " (" lsdel ),
 699 and
 700 .IR htree_dump .
 701 The specific pager can explicitly specified by the
 702 .B DEBUGFS_PAGER
 703 environment variable, and if it is not set, by the
 704 .B PAGER
 705 environment variable.
 706 .IP
 707 Note that since a pager is always used, the
 708 .BR less (1)
 709 pager is not particularly appropriate, since it clears the screen before
 710 displaying the output of the command and clears the output the screen
 711 when the pager is exited.  Many users prefer to use the
 712 .BR less (1)
 713 pager for most purposes, which is why the
 714 .B DEBUGFS_PAGER
 715 environment variable is available to override the more general
 716 .B PAGER
 717 environment variable.
 718 .SH AUTHOR
 719 .B debugfs
 720 was written by Theodore Ts'o <tytso@mit.edu>.
 721 .SH SEE ALSO
 722 .BR dumpe2fs (8),
 723 .BR tune2fs (8),
 724 .BR e2fsck (8),
 725 .BR mke2fs (8),
 726 .BR ext4 (5)