# badblocks

## 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.
    


## AVAILABILITY



           **badblocks** is part of the e2fsprogs package and is available from
           http://e2fsprogs.sourceforge.net.
    


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