badblocks - search a device for bad blocks
badblocks [ -svwnfBX ] [ -b block_size
] [ -c blocks_at_once ] [ -d read_delay_factor ]
[ -e max_bad_blocks ] [ -i input_file ] [
-o output_file ] [ -p num_passes ] [ -t
test_pattern ] device [ last_block ] [
first_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. 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.
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 file system.
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.
- -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.
- -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.
- -f
- 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 file system 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 file
system, in a format suitable for use with this option.
- -n
- 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.
- -s
- 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.
- -v
- Verbose mode. Will write the number of read errors, write errors and data-
corruptions to stderr.
- -w
- 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.
- -B
- Use buffered I/O and do not use Direct I/O, even if it is available.
- -X
- 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.
The -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.
badblocks was written by Remy Card
<Remy.Card@linux.org>. Current maintainer is Theodore Ts'o
<tytso@alum.mit.edu>. Non-destructive read/write test implemented by
David Beattie <dbeattie@softhome.net>.
badblocks is part of the e2fsprogs package and is available
from http://e2fsprogs.sourceforge.net.