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badblocks - search a device for bad blocks
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 ]
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.
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
- Normally, badblocks will refuse to do a read/write or a nondestructive
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 overridden
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
- -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
- -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 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 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 one pattern before proceeding to the
- Use non-destructive read-write mode. By default only a nondestructive
read-only test is done. This option must not be
combined with the -w option, as they are mutually exclusive.
- Show the progress of the scan by writing out the block numbers
as they are checked.
- Verbose mode.
- 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.
- Internal flag only to be used by e2fsck(8)
bypasses the exclusive mode in-use device safety check.
Never use the -w option on a 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.
badblocks was written by Remy Card <Remy.Card@linux.org>. Current
maintainer is Theodore Ts’o <firstname.lastname@example.org>. Non-destructive
read/write test implemented by David Beattie <email@example.com>.
badblocks is part of the e2fsprogs package and is available from
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