BADBLOCKS linux command manual

BADBLOCKS(8)                                                       BADBLOCKS(8)

       badblocks - search a device for bad blocks

       badblocks  [  -svwnf  ]  [  -b block-size ] [ -c blocks_at_once ] [ -i
       input_file ] [ -o output_file ] [ -p num_passes ] [ -t test_pattern  ]
       device [ last-block ] [ start-block ]

       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.
       start-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.   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.

       -b block-size
              Specify the size of blocks in bytes.

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

       -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  potentially  crash  and/or  damage  the
              filesystem  even if it is mounted read-only.  This can be over-
              riden using the -f flag, but should almost never be used --- if
              you think you're smarter than the badblocks program, you almost
              certainly 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 testing 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

       -o output_file
              Write the list of bad blocks to the  specified  file.   Without
              this  option,  badblocks displays the list on its standard out-
              put.  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 discov-
              ered in num_passes consecutive scans of the disk.   Default  is
              0, meaning badblocks will exit after the first pass.

       -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  inclusive,  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 specifiying the -t option for
              each  test  pattern  desired.  For read-only mode only a single
              pattern 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 multiple patterns are speci-
              fied then all blocks will be tested with an one pattern  before
              proceeding to the next pattern.

       -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.

       -s     Show  the progress of the scan by writing out the block numbers
              as they are checked.

       -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 combined with the -n
              option, as they are mutually exclusive.

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

       badblocks  was  written  by  Remy Card .  Current
       maintainer is  Theodore  Ts'o  .   Non-destructive
       read/write  test implemented by David Beattie .

       badblocks is part of the  e2fsprogs  package  and  is  available  from

       e2fsck(8), mke2fs(8)

E2fsprogs version 1.35          February 2004                    BADBLOCKS(8)