is used to search for bad blocks on a device (usually a disk partition).
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
is going to be fed to the
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. For this reason, it is strongly recommended that
directly, but rather use the
option of the
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 16.
Increasing this number will increase the efficiency of
but also will increase its memory usage.
needs memory proportional to the number of blocks tested at once, in
read-only mode, proportional to twice that number in read-write mode,
and proportional to three times that number in non-destructive read-write
mode. If you set the number-of-blocks parameter to too high a value,
will exit almost immediately with an out-of-memory error "while allocating
buffers". If you set it too low, however, for a non-destructive-write-mode
test, then it's possble for questionable blocks on an unreliable
hard drive to be hidden by the effects of the hard disk track buffer.
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 overriden using the
flag, but should almost never be used --- if you think you're smarter
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.
will skip testing these blocks since they are known to be bad. If
is specified as "-", the list will be read from the standard input.
Blocks listed in this list will be omitted from the list of
bad blocks produced on the standard output or in the output file.
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.
Write the list of bad blocks to the specified file. Without this option,
displays the list on its standard output. The format of this file is suitable
for use by the
Repeat scanning the disk until there are no new blocks discovered in
num_passes consecutive scans of the disk.
Default is 0, meaning
will exit after the first pass.
Specify a test pattern to be read (and written) to disk blocks. The
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
For read/write (-w) and non-destructive (-n) modes,
one or more test patterns may be specified by specifiying the
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.
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
option, as they are mutually exclusive.
Show the progress of the scan by writing out the block numbers as they
Use write-mode test. With this option,
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
option, as they are mutually exclusive.
Never use the
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
option instead. It is slower, but it will preserve your data.