Provided by: e2fsprogs_1.44.1-1ubuntu1.4_amd64 
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 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 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.
-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.
AUTHOR
badblocks was written by Remy Card <Remy.Card@linux.org>. Current maintainer is Theodore
Ts'o <tytso@alum.mit.edu>. Non-destructive read/write test implemented by David Beattie
<dbeattie@softhome.net>.
AVAILABILITY
badblocks is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.
SEE ALSO
e2fsck(8), mke2fs(8)