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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 ] [ -e max_bad_blocks ] [ -d
       read_delay_factor ] [ -i input_file ] [ -o output_file ] [ -p num_passes ] [ -t  test_pat‐
       tern ] 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 spec‐
       ified 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 pro‐
       grams,  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  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.

       -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.

       -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 per‐
              formed. 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.

       -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 filesystem even if it is mounted read-only.  This can be overrid‐
              den 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 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 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  pat‐
              tern.   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 pre‐
              viously  been written to the disk - if not, large numbers of blocks will fail veri‐
              fication.  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- corrup‐
              tions 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 exclu‐
              sive 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 .  Current maintainer is  Theodore
       Ts'o  .   Non-destructive read/write test implemented by David Beattie
       .

AVAILABILITY
       badblocks is part of the e2fsprogs package and is available from  http://e2fsprogs.source‐
       forge.net.

SEE ALSO
       e2fsck(8), mke2fs(8)

E2fsprogs version 1.42.13                    May 2015                                BADBLOCKS(8)

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