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BADBLOCKS(8)                                                      BADBLOCKS(8)



NAME
       badblocks - search a device for bad blocks

SYNOPSIS
       badblocks  [ -svwnf ] [ -b block-size ] [ -c blocks_at_once ] [ -e max_bad_blocks ]
       [ -d read_delay_factor ] [ -i input_file ] [ -o output_file ] [ -p num_passes  ]  [
       -t test_pattern ] device [ last-block ] [ first-block ]

DESCRIPTION
       badblocks  is used to search for bad blocks on a device (usually a disk partition).
       device is the special file corresponding to the device (e.g /dev/hdc1).  last-block
       is  the  last  block  to  be checked; if it is not specified, the last block on the
       device is used as a default.  first-block is an optional parameter  specifying  the
       starting block number for the test, which allows the testing to start in the middle
       of the disk.  If it is not specified the first block on  the  disk  is  used  as  a
       default.

       Important  note:  If  the  output  of badblocks is going to be fed to the e2fsck or
       mke2fs programs, it is important that the block size is properly  specified,  since
       the  block  numbers which are generated are very dependent on the block size in use
       by the filesystem.  For this reason, it is strongly recommended that users not  run
       badblocks directly, but rather use the -c option of the e2fsck and mke2fs programs.

OPTIONS
       -b block-size
              Specify the size of blocks in bytes.  The default is 1024.

       -c number of blocks
              is the number of blocks which are tested at a time.  The default is 64.

       -e max bad block count
              Specify a maximum number of  bad  blocks  before  aborting  the  test.   The
              default is 0, meaning the test will continue until the end of the test range
              is reached.

       -d read delay factor
              This parameter, if passed and non-zero,  will  cause  bad  blocks  to  sleep
              between reads if there were no errors encountered in the read operation; the
              delay will be calculated as a percentage of the time it took  for  the  read
              operation  to  be  performed. In other words, a value of 100 will cause each
              read to be delayed by the amount the previous read took, and a value of  200
              by twice the amount.

       -f     Normally, badblocks will refuse to do a read/write or a non-destructive test
              on a device which is mounted, since either can cause the  system  to  poten-
              tially  crash  and/or damage the filesystem even if it is mounted read-only.
              This can be overridden using the -f flag, but should almost  never  be  used
              ---  if you think you're smarter than the badblocks program, you almost cer-
              tainly aren't.  The only time when this option might be safe to  use  is  if
              the /etc/mtab file is incorrect, and the device really isn't mounted.

       -i input_file
              Read a list of already existing known bad blocks.  Badblocks will skip test-
              ing these blocks since they are known to be bad.  If input_file is specified
              as  "-",  the  list  will be read from the standard input.  Blocks listed in
              this list will be omitted from the list of new bad blocks  produced  on  the
              standard  output or in the output file.  The -b option of dumpe2fs(8) can be
              used to retrieve the list of blocks currently  marked  bad  on  an  existing
              filesystem, in a format suitable for use with this option.

       -n     Use  non-destructive  read-write  mode.   By  default only a non-destructive
              read-only test is done.  This option  must  not  be  combined  with  the  -w
              option, as they are mutually exclusive.

       -o output_file
              Write  the  list  of bad blocks to the specified file.  Without this option,
              badblocks displays the list on its standard output.  The format of this file
              is suitable for use by the -l option in e2fsck(8) or mke2fs(8).

       -p num_passes
              Repeat  scanning  the  disk  until  there  are  no  new blocks discovered in
              num_passes consecutive scans of the disk.  Default is 0,  meaning  badblocks
              will exit after the first pass.

       -s     Show  the progress of the scan by writing out rough percentage completion of
              the current badblocks pass over the disk.  Note that badblocks may do multi-
              ple  test  passes  over  the  disk,  in particular if the -p or -w option is
              requested by the user.

       -t test_pattern
              Specify a test pattern to be  read  (and  written)  to  disk  blocks.    The
              test_pattern  may either be a numeric value between 0 and ULONG_MAX-1 inclu-
              sive, or the word "random", which specifies that the block should be  filled
              with  a  random  bit  pattern.  For read/write (-w) and non-destructive (-n)
              modes, one or more test patterns may  be  specified  by  specifying  the  -t
              option for each test pattern desired.  For read-only mode only a single pat-
              tern may be specified and it may not be "random".  Read-only testing with  a
              pattern  assumes  that  the specified pattern has previously been written to
              the disk - if not, large numbers of blocks will fail verification.  If  mul-
              tiple patterns are specified then all blocks will be tested with one pattern
              before proceeding to the next pattern.

       -v     Verbose mode.

       -w     Use write-mode test. With this option, badblocks scans  for  bad  blocks  by
              writing some patterns (0xaa, 0x55, 0xff, 0x00) on every block of the device,
              reading every block and comparing the contents.  This option may not be com-
              bined with the -n option, as they are mutually exclusive.

       -X     Internal  flag  only to be used by e2fsck(8) and mke2fs(8).  It bypasses the
              exclusive mode in-use device safety check.

WARNING
       Never use the -w option on a device  containing  an  existing  file  system.   This
       option  erases data!  If you want to do write-mode testing on an existing file sys-
       tem, use the -n option instead.  It is slower, but it will preserve your data.

       The -e option will cause badblocks to output a  possibly  incomplete  list  of  bad
       blocks.  Therefore it is recommended to use it only when one wants to know if there
       are any bad blocks at all on the device, and not when the list  of  bad  blocks  is
       wanted.

AUTHOR
       badblocks  was  written  by Remy Card <Remy.Card AT linux.org>.  Current maintainer is
       Theodore Ts'o <tytso AT alum.edu>.  Non-destructive read/write test implemented by
       David Beattie <dbeattie AT softhome.net>.

AVAILABILITY
       badblocks   is   part   of   the   e2fsprogs   package   and   is   available  from
       http://e2fsprogs.sourceforge.net.

SEE ALSO
       e2fsck(8), mke2fs(8)



E2fsprogs version 1.41.12          May 2010                       BADBLOCKS(8)

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