From Linux Man Pages
badblocks - search a device for bad blocks
SYNOPSIS
badblocks [ -svwnf ] [ -b block-size ] [ -c blocks_at_once ] [ -i input_file ] [ -o output_file ] [ -p num_passes
] [ -t test_pattern ] device [ last-block ] [ start-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. start-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 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.
-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 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 filesystem, in a format suitable for use with this option.
-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.
-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.
-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.
-s Show the progress of the scan by writing out the block numbers as they are checked.
-v Verbose mode.
-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.
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.
AVAILABILITY
badblocks is part of the e2fsprogs package and is available from http://e2fsprogs.sourceforge.net.
RELATED
e2fsck(8), mke2fs(8)
CATEGORY