badblocks(8) - Online Manual Page Of Unix/Linux

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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 out-
put_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 spec-
ified 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 pro-
grams, 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 overri-
den 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 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 inclusive, or the word
"random", which specifies that the block should be filled with a random bit pat-
tern. For read/write (-w) and non-destructive (-n) modes, one or more test pat-
terns 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 specified 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 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 <>. Current maintainer is Theodore
Ts'o <>. Non-destructive read/write test implemented by David Beattie
<>.

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