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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-
              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 AT linux.org>.  Current
       maintainer  is  Theodore  Ts'o  <tytso AT alum.edu>.   Non-destructive
       read/write test implemented by David Beattie <dbeattie AT 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 1.45.6          March 2020                      BADBLOCKS(8)