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BADBLOCKS(8)		    System Manager's Manual		  BADBLOCKS(8)

NAME
       badblocks - search a device for bad blocks

SYNOPSIS
       badblocks  [  -svwnfBX  ]  [ -b block_size ] [ -c blocks_at_once	] [ -d
       read_delay_factor ] [ -e	max_bad_blocks ] [ -i input_file ] [  -o  out-
       put_file	 ] [ -p	num_passes ] [ -t test_pattern ] 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 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.

       -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.

       -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.

       -f     Normally,	 badblocks will	refuse to do a read/write or a non-de-
	      structive	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 us-
	      ing  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.

       -n     Use non-destructive read-write mode.  By default only a  non-de-
	      structive	 read-only test	is done.  This option must not be com-
	      bined 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 discov-
	      ered 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.  Will write	the number of read errors,  write  er-
	      rors and data- corruptions to stderr.

       -w     Use  write-mode  test. With this option, badblocks scans for bad
	      blocks by	writing	some patterns (0xaa, 0x55, 0xff, 0x00) on  ev-
	      ery  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.

       -B     Use buffered I/O and do not use Direct I/O, even if it is	avail-
	      able.

       -X     Internal flag only to be used by e2fsck(8)  and  mke2fs(8).   It
	      bypasses the exclusive 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.sourceforge.net.

SEE ALSO
       e2fsck(8), mke2fs(8)

E2fsprogs version 1.43.4	 January 2017			  BADBLOCKS(8)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | WARNING | AUTHOR | AVAILABILITY | SEE ALSO

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