badblocks
BADBLOCKS(8) BADBLOCKS(8)
NAME
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. 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.
-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 over-
riden 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 out-
put. 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 discov-
ered 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 specifiying 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 speci-
fied then all blocks will be tested with an 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 an device containing an existing file sys-
tem. 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.
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)
E2fsprogs version 1.35 February 2004 BADBLOCKS(8)
