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 ] 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 num-
ber 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 prop-
erly specified, since the block numbers which are generated is 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 16. Increasing this number will increase the efficiency of
badblocks but also will increase its memory usage. Badblocks
needs memory proportional to the number of blocks tested at
once, in read-only mode, proportional to twice that number in
read-write mode, and proportional to three times that number in
non-destructive read-write mode. If you set the number-of-
blocks parameter to too high a value, badblocks will exit almost
immediately with an out-of-memory error "while allocating
buffers". If you set it too low, however, for a non-destruc-
tive-write-mode test, then it's possble for questionable blocks
on an unreliable hard drive to be hidden by the effects of the
hard disk track buffer.
-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 filesys-
tem even if it is mounted read-only. This can be overriden
using the -f flag, but should almost never be used --- if you
think you're smarter than the badblocks program, you almost cer-
tainly 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 discov-
ered in num_passes consecutive scans of the disk. Default is 0,
meaning badblocks will exit after the first pass.
-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 1.32 November 2002 BADBLOCKS(8)
