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-
	      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.

       -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 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
	      errors 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
	      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.

       -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 1.43.5	  August 2017			  BADBLOCKS(8)