badblocks - phpMan

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
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 poten-
tially 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 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 test-
ing 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 inclu-
sive, 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 pat-
tern 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 mul-
tiple patterns are specified then all blocks will be tested with an one pat-
tern 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 com-
bined with the -n option, as they are mutually exclusive.

WARNING
Never use the -w option on an device containing an existing file system. This
option erases data! If you want to do write-mode testing on an existing file sys-
tem, use the -n option instead. It is slower, but it will preserve your data.

AUTHOR
badblocks was written by Remy Card <Remy.Card AT linux.org>. Current maintainer is
Theodore Ts’o <tytso AT alum.edu>. Non-destructive read/write test implemented by
David Beattie <dbeattie AT softhome.net>.

AVAILABILITY
badblocks is part of the e2fsprogs package and is available from
http://e2fsprogs.sourceforge.net.