− search a device for bad blocks
[ −svwnfBX ] [ −b
block-size ] [ −c blocks_at_once
] [ −e max_bad_blocks ] [
−d read_delay_factor ] [ −i
input_file ] [ −o output_file ] [
−p num_passes ] [ −t
test_pattern ] device [ last-block ] [
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.
first-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.
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
Specify the size of blocks in
bytes. The default is 1024.
−c number of
is the number of blocks which
are tested at a time. The default is 64.
−e max bad
Specify a maximum number of bad
blocks before aborting the test. The default is 0, meaning
the test will continue until the end of the test range is
−d read delay
This parameter, if passed and
non-zero, will cause bad blocks to sleep between reads if
there were no errors encountered in the read operation; the
delay will be calculated as a percentage of the time it took
for the read operation to be performed. In other words, a
value of 100 will cause each read to be delayed by the
amount the previous read took, and a value of 200 by twice
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 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 isn’t mounted.
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
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
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).
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.
Show the progress of the scan by writing out rough
percentage completion of the current badblocks pass over the
disk. Note that badblocks may do multiple test passes over
the disk, in particular if the −p or
−w option is requested by the user.
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 next pattern.
Verbose mode. Will write the number of read errors,
write errors and data- corruptions to stderr.
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
Use buffered I/O and do not use Direct I/O, even if it
Internal flag only to be used by e2fsck(8) and
mke2fs(8). It 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.
−e option will cause badblocks to output a
possibly incomplete list of bad blocks. Therefore it is
recommended to use it only when one wants to know if there
are any bad blocks at all on the device, and not when the
list of bad blocks is wanted.
was written by Remy Card <Remy.Card@linux.org>.
Current maintainer is Theodore Ts’o
<email@example.com>. Non-destructive read/write test
implemented by David Beattie
is part of the e2fsprogs package and is available from