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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 ] [ -i
       input_file ] [ -o output_file ] [ -p num_passes ] [ -t  test_pattern  ]
       device [ last-block ] [ start-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.
       start-block is an optional parameter specifying the starting block num-
       ber 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 prop-
       erly 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.

       -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 filesys-
	      tem  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  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 exist-
	      ing 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  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 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.

       -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.

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

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

SEE ALSO
       e2fsck(8), mke2fs(8)



E2fsprogs version 1.39		   May 2006			  BADBLOCKS(8)
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