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 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.
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 param
eter 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-destructive-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 this can cause the system to poten
tially crash. This can be overriden using the -
flag, but this should not be done under normal cir
cumstances. The only time when this option might
be safe 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
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 filesys
tem, 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.
-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 con
tents. This option may not be compiled with the -n
option, as they are mutually exclusive.
WARNING
Never use the -w option on an device containing an exist
ing 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.
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 Beat
tie <dbeattie@softhome.net>.
AVAILABILITY
badblocks is part of the e2fsprogs package and is avail
able from http://e2fsprogs.sourceforge.net.
e2fsck(8), mke2fs(8)
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