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NAME    [Toc]    [Back]

       badblocks - search a device for bad blocks

SYNOPSIS    [Toc]    [Back]

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

DESCRIPTION    [Toc]    [Back]

       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  is  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.

OPTIONS    [Toc]    [Back]

       -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 16.  Increasing this number will increase the	efficiency  of
	      badblocks  but  also  will increase its memory usage.  Badblocks
	      needs memory proportional to the	number	of  blocks  tested  at
	      once,  in  read-only  mode, proportional to twice that number in
	      read-write mode, and proportional to three times that number  in
	      non-destructive  read-write  mode.   If  you  set the number-ofblocks
 parameter to too high a value, badblocks will exit almost
	      immediately   with  an  out-of-memory  error  "while  allocating
	      buffers".  If you set it too low, however,  for  a  non-destructive-write-mode
  test, then it's possble for questionable blocks
	      on an unreliable hard drive to be hidden by the effects  of  the
	      hard disk track buffer.

       -f     Normally,  badblocks  will  refuse  to do a read/write or a nondestructive
 test on a device which is mounted, since either  can
	      cause  the  system  to potentially crash; even a non-destructive
	      test can damage a mounted filesystem.   This  can  be  overriden
	      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 option.

       -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.

       -n     Use  non-destructive  read-write	mode.	By default only a nondestructive
 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.

WARNING    [Toc]    [Back]

       Never use the -w option on an 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 preserve your data.

AUTHOR    [Toc]    [Back]

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

AVAILABILITY    [Toc]    [Back]

       badblocks  is  part  of	the  e2fsprogs	package  and is available from

SEE ALSO    [Toc]    [Back]

       e2fsck(8), mke2fs(8)

E2fsprogs version 1.27		  March 2002			  BADBLOCKS(8)
[ Back ]
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