BADBLOCKS(8)              (August 2021)              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 (usu-
          ally a disk partition).  device is the special file corre-
          sponding 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 num-
          bers 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 pro-
          grams.

     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

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               the test.  The default is 0, meaning the test will con-
               tinue 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 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 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 per-
               centage 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

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               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 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 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 pro-
               ceeding 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

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          from http://e2fsprogs.sourceforge.net.

     SEE ALSO
          e2fsck(8), mke2fs(8)

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