1BADBLOCKS(8)                System Manager's Manual               BADBLOCKS(8)
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NAME

6       badblocks - search a device for bad blocks
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SYNOPSIS

9       badblocks  [  -svwnf  ]  [  -b  block-size ] [ -c blocks_at_once ] [ -e
10       max_bad_blocks ] [ -d read_delay_factor ] [ -i input_file ] [  -o  out‐
11       put_file  ] [ -p num_passes ] [ -t test_pattern ] device [ last-block ]
12       [ first-block ]
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DESCRIPTION

15       badblocks is used to search for bad blocks on a device (usually a  disk
16       partition).   device  is  the  special file corresponding to the device
17       (e.g /dev/hdc1).  last-block is the last block to be checked; if it  is
18       not  specified,  the  last  block  on  the device is used as a default.
19       first-block is an optional parameter specifying the starting block num‐
20       ber  for  the  test, which allows the testing to start in the middle of
21       the disk.  If it is not specified the first block on the disk  is  used
22       as a default.
23
24       Important  note:  If  the output of badblocks is going to be fed to the
25       e2fsck or mke2fs programs, it is important that the block size is prop‐
26       erly  specified,  since  the block numbers which are generated are very
27       dependent on the block size in use by the filesystem.  For this reason,
28       it  is  strongly recommended that users not run badblocks directly, but
29       rather use the -c option of the e2fsck and mke2fs programs.
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OPTIONS

32       -b block-size
33              Specify the size of blocks in bytes.  The default is 1024.
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35       -c number of blocks
36              is the number of blocks which are tested at a time.  The default
37              is 64.
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39       -e max bad block count
40              Specify a maximum number of bad blocks before aborting the test.
41              The default is 0, meaning the test will continue until  the  end
42              of the test range is reached.
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44       -d read delay factor
45              This parameter, if passed and non-zero, will cause bad blocks to
46              sleep between reads if there were no errors encountered  in  the
47              read  operation; the delay will be calculated as a percentage of
48              the time it took for the read  operation  to  be  performed.  In
49              other  words,  a value of 100 will cause each read to be delayed
50              by the amount the previous read took, and  a  value  of  200  by
51              twice the amount.
52
53       -f     Normally,  badblocks  will  refuse  to do a read/write or a non-
54              destructive test on a device which is mounted, since either  can
55              cause the system to potentially crash and/or damage the filesys‐
56              tem even if it is mounted read-only.   This  can  be  overridden
57              using  the  -f  flag, but should almost never be used --- if you
58              think you're smarter than the badblocks program, you almost cer‐
59              tainly  aren't.  The only time when this option might be safe to
60              use is if the /etc/mtab file is incorrect, and the device really
61              isn't mounted.
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63       -i input_file
64              Read  a  list  of  already existing known bad blocks.  Badblocks
65              will skip testing these blocks since they are known to  be  bad.
66              If  input_file  is  specified as "-", the list will be read from
67              the standard input.  Blocks listed in this list will be  omitted
68              from  the list of new bad blocks produced on the standard output
69              or in the output file.  The -b option of dumpe2fs(8) can be used
70              to retrieve the list of blocks currently marked bad on an exist‐
71              ing filesystem, in a format suitable for use with this option.
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73       -n     Use non-destructive read-write mode.  By  default  only  a  non-
74              destructive  read-only  test  is  done.  This option must not be
75              combined with the -w option, as they are mutually exclusive.
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77       -o output_file
78              Write the list of bad blocks to  the  specified  file.   Without
79              this option, badblocks displays the list on its standard output.
80              The format of this file is suitable for use by the -l option  in
81              e2fsck(8) or mke2fs(8).
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83       -p num_passes
84              Repeat  scanning  the disk until there are no new blocks discov‐
85              ered in num_passes consecutive scans of the disk.  Default is 0,
86              meaning badblocks will exit after the first pass.
87
88       -s     Show  the  progress  of the scan by writing out rough percentage
89              completion of the current badblocks pass over  the  disk.   Note
90              that  badblocks  may  do  multiple test passes over the disk, in
91              particular if the -p or -w option is requested by the user.
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93       -t test_pattern
94              Specify a test pattern to be read (and written) to disk  blocks.
95              The  test_pattern  may  either  be a numeric value between 0 and
96              ULONG_MAX-1 inclusive, or the  word  "random",  which  specifies
97              that  the block should be filled with a random bit pattern.  For
98              read/write (-w) and non-destructive (-n) modes, one or more test
99              patterns  may  be specified by specifying the -t option for each
100              test pattern desired.  For read-only mode only a single  pattern
101              may  be specified and it may not be "random".  Read-only testing
102              with a pattern assumes that the specified pattern has previously
103              been  written to the disk - if not, large numbers of blocks will
104              fail verification.  If multiple patterns are specified then  all
105              blocks  will be tested with one pattern before proceeding to the
106              next pattern.
107
108       -v     Verbose mode.
109
110       -w     Use write-mode test. With this option, badblocks scans  for  bad
111              blocks  by  writing  some  patterns  (0xaa, 0x55, 0xff, 0x00) on
112              every block of the device, reading every block and comparing the
113              contents.   This  option may not be combined with the -n option,
114              as they are mutually exclusive.
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116       -X     Internal flag only to be used by e2fsck(8)  and  mke2fs(8).   It
117              bypasses the exclusive mode in-use device safety check.
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WARNING

120       Never use the -w option on a device containing an existing file system.
121       This option erases data!  If you want to do write-mode  testing  on  an
122       existing  file system, use the -n option instead.  It is slower, but it
123       will preserve your data.
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125       The -e option will cause badblocks to output a possibly incomplete list
126       of  bad  blocks.  Therefore  it  is recommended to use it only when one
127       wants to know if there are any bad blocks at all on the device, and not
128       when the list of bad blocks is wanted.
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AUTHOR

131       badblocks  was  written  by  Remy  Card <Remy.Card@linux.org>.  Current
132       maintainer  is  Theodore  Ts'o  <tytso@alum.mit.edu>.   Non-destructive
133       read/write test implemented by David Beattie <dbeattie@softhome.net>.
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AVAILABILITY

136       badblocks  is  part  of  the  e2fsprogs  package  and is available from
137       http://e2fsprogs.sourceforge.net.
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SEE ALSO

140       e2fsck(8), mke2fs(8)
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144E2fsprogs version 1.41.12          May 2010                       BADBLOCKS(8)
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