WIPE

Section: User Commands (1)
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NAME

wipe - secure file deletion utility

 

SYNOPSIS

wipe

[-ucwsiIhfFdDnNvVzZrRtTkKaA] [-B(count)] [-S(size)] [-C(size)] [-o[size] -O] [-l[0-2]] [-x[1-32] -X] [-p(1-32)] [-b(0-255)] [files]

 

DEFAULT

wipe -ZdntVAkO -S512 -C4096 -l1 -x8 -p1

 

DESCRIPTION

Wipe is a secure file wiping utility. There are some low level issues that must be taken into consideration. One of these is that there must be some sort of write barrier between passes. Wipe uses fdatasync(2) (or fsync(2)) as a write barrier, or if fsync(2) isn't available, the file is opened with the O_DSYNC or O_SYNC flag. For wipe to be effective, each pass must be completely written. To ensure this, the drive must support some form of a write barrier, write cache flush, or write cache disabling. SCSI supports ordered command tags, has a force media access bit for commands, and write cache can be disable on mode page 8. IDE/ATA drives support write cache flushes and write cache disabling. Unfortunetly, not all drives actually disable write cache when asked to. Those drives are broken. Write caching should always be disabled, unless your system is battery backed and always powers down cleanly

Under linux, the mount option "mand" must be used (see linux/Documentation/mandatory.txt) for mandatory file locks to be enabled. Wipe should make it extremely difficult for all but the most determined person(s) to recover the original plaintext data. Utilities such as PGP and the GNU Privacy Guard provide strong encryption, but encryption is useless if the original plaintext can be recovered. When using PGP and GPG, temporary files that are disk-backed should be stored on an encrypted file system. That way, the plaintext never hits the platters. Wipe is designed for situations where an encrypted file system isn't practical.

Wipe uses /dev/urandom, or if unavailable, /dev/random, as a source for entropy. The Mersenne Twister PRNG is used for speed. The MT site is at:

http://www.math.keio.ac.jp/~matumoto/emt.html

For more information on the secure deletion of magnetic media and solid state storage devices (such as DRAM) see the USENIX article by Peter Gutmann at:

http://www.cs.auckland.ac.nz/~pgut001/secure_del.html

 

OPTIONS

-h
Display help screen. Shows options and what they do.
-u
usage - shows options
-c
shows copywrite information
-w
shows warranty
-i
interactive - prompt whether to remove each file explicitly checks file permissions
-I
disables interaction
-f
forces file wiping and suppresses permission warnings
-r or -R
recursion - traverse subdirectories
-s
silent - disable percent reporting and some warnings
-V
verbose - shows percentage if file size is above a certain limit (see wipe -h)
-v
force verbose - always show percentage
-d and -D
delete (-d) or keep (-D) after wiping
-n and -N
delete (-n) or skip (-N) fifos, sockets, sym links, and char devices
-k and -K
lock (-k) or don't lock (-K) files during wiping
-z
zero-out file - performs a single pass of zeros
-Z
perform normal passes - overrides -z
-t and -T
enable (-t) or disable (-T) static passes
-a and -A
write until out of space (-a) or don't (-A)
-o and -O
write [size] to stdout (-o) or use files (-O)

Since wipe does not have specific support for char devs, like it does for block devs, this is the preferred method of wiping them, such as tape drives; eg, wipe -za -o | buffer > /dev/nst0 It can also be used for block devs; eg wipe -To | dd count=size of=blkdev

You can also use this to create files containing pseudo-random output from the MT PRNG; eg, wipe -To10240 -x1 > prand

For static passes, you must specify a stdout length.

-B
override block device sector count
-S
override block device sector size
-C
chunk size - the maximum file buffer size
-l
sets generic security level

level 0, the PRNG is only seeded once

level 1, the PRNG is seeded once per file

level 2, the PRNG is seeded once per random pass

-x
enables random passes and optionally, how many random passes to perform - note that this option now sets the number of random passes per wipe loop - in other words, the total number of random passes will be random passes * wipe loops (-p)
-X
disable random passes
-p
loop passes - perform wipe sequence x times, including random passes
-b
custom byte - overwrite once with a specific byte

 

FILES

/dev/urandom
Wipe uses this character device for a source of entropy
/dev/random
Wipe falls back to using this if /dev/urandom is not available

 

DIAGNOSTICS

If an error occurs, the exit code will be the errno value. An exit code of 2 indicates bad usage.

 

BUGS

Wipe does not work on log structured file systems, or any other type of file system or block device that reallocates sectors on write.

Some programs are vulnerable to symlink races. To avoid this problem with wipe, only wipe files in directories that are not writable by untrusted users.

 

NOTES

Other file wiping utilities

There are several other file wipers available.

Another "wipe" by Berke Durak <durakb@crit2.univ-montp2.fr>

Colin Plumb's <colin@nyx.net> sterilize.

Todd Burgess's <tburgess@eddie.cis.uoguelph.ca> srm is available on sunsite/metalab in

ftp://metalab.unc.edu/pub/Linux/system/filesystems/

 

AUTHOR

Copyright (C) 1998-2003 by Tom Vier <nester@users.sf.net>

 

AVAILABILITY

http://wipe.sf.net/

 

SEE ALSO

/usr/doc/wipe/README


 

Index

NAME
SYNOPSIS
DEFAULT
DESCRIPTION
OPTIONS
FILES
DIAGNOSTICS
BUGS
NOTES
AUTHOR
AVAILABILITY
SEE ALSO

linux.jgfs.net manual pages