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
       output_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
       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 are
       very dependent on the block size in use by the file system.  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 file
	      system 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
	      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 file system, 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 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
	      available.

       -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 1.47.3	   July 2025			  BADBLOCKS(8)