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

       badblocks - search a device for bad blocks

       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 ]

       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

       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.

       -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

       -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

       -X     Internal flag only to be used by e2fsck(8) and mke2fs(8).  It
              bypasses the exclusive mode in-use device safety check.

       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.

       badblocks was written by Remy Card <>.  Current
       maintainer is Theodore Ts'o <>.  Non-destructive
       read/write test implemented by David Beattie <>.

       badblocks is part of the e2fsprogs package and is available from

       e2fsck(8), mke2fs(8)

E2fsprogs version 1.46.4           August 2021                      BADBLOCKS(8)