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BADBLOCKS(8)                                                      BADBLOCKS(8)

       badblocks - search a device for bad blocks

       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 ]

       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 speci-
       fied, 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  bad-
       blocks directly, but rather use the -c option of the e2fsck and mke2fs programs.

       -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 potentially 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 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

       -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 out-
              put or in the output file.  The -b option of dumpe2fs(8) can be used to retrieve the list of blocks cur-
              rently 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

       -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 multiple 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 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 specifying 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 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 combined 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.

       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 system, use the -n option instead.  It is slower, but it will pre-
       serve your data.

       The -e option will cause badblocks to output a possibly incomplete list of bad blocks. Therefore it  is  recom-
       mended 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.

       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 1.41.12          May 2010                       BADBLOCKS(8)