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