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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_pat-
       tern ] 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 spec-
       ified 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 pro-
       grams,  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 per-
	      formed. 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 overrid-
	      den 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.

       -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  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  pat-
	      tern.   For  read/write  (-w) and non-destructive (-n) modes, one or more test pat-
	      terns 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 "ran-
	      dom".  Read-only testing with a pattern assumes that the specified pattern has pre-
	      viously  been written to the disk - if not, large numbers of blocks will fail veri-
	      fication.  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  exclu-
	      sive 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 system, 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@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.source-
       forge.net.

SEE ALSO
       e2fsck(8), mke2fs(8)

E2fsprogs version 1.41.14		  December 2010 			     BADBLOCKS(8)
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