Unix for Beginners
Unix Shell Programming
Unix Useful References
Unix Useful Resources
Copyright © 2014 by tutorialspoint
badblocks - Unix, Linux Command
badblocks - search a device for bad blocks
-b block-size ]
-c blocks_at_once ]
-i input_file ]
-o output_file ]
-p num_passes ]
-t test_pattern ]
last-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
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
badblocks directly, but rather use the
-c option of the
-b block-size |
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 is 64.
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 youre smarter
badblocks program, you almost certainly arent. The only time when this option
might be safe to use is if the /etc/mtab file is incorrect, and the device
really isnt 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.
-b option of
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
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.
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.
Show the progress of the scan by writing out the block numbers as they
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.
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 Tso <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