badblocks - search a device for bad blocks
] [ -b block_size
] [ -c
] [ -d read_delay_factor
] [ -e
] [ -i input_file
] [ -o
] [ -p num_passes
] [ -t
] [ first_block
is used to search for bad blocks on a device (usually a disk
is the special file corresponding to the device (e.g
is the last block to be checked; if it is
not specified, the last block on the device is used as a default.
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.
If the output of badblocks
is going to be fed to
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
but rather use the -c
option of the e2fsck
- -b block_size
- Specify the size of blocks in bytes. The default is
- -c number of blocks
- is the number of blocks which are tested at a time. The
default is 64.
- -d read delay factor
- 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 the amount.
- -e max bad block count
- 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 reached.
- 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.
- -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.
- 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.
- -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.
- 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.
- -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 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 is
- Internal flag only to be used by e2fsck(8) and
mke2fs(8). It bypasses the exclusive mode in-use device safety
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.
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 <firstname.lastname@example.org>. Non-destructive
read/write test implemented by David Beattie <email@example.com>.
is part of the e2fsprogs package and is available from