---
name: "srm"
section: "1"
platform: "linux"
package: "secure-delete"
version: "3.1-12"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/srm"
---

# srm(1)

secure remove (secure\_deletion toolkit)

## NAME

srm - secure remove (secure\_deletion toolkit)

## SYNOPSIS

**srm \[-d\] \[-f\] \[-l\] \[-l\] \[-r\] \[-v\] \[-z\] files**

## DESCRIPTION

*srm* is designed to delete data on mediums in a secure manner which can not be recovered by thieves, law enforcement or other threats. The wipe algorithm is based on the paper "Secure Deletion of Data from Magnetic and Solid-State Memory" presented at the 6th Usenix Security Symposium by Peter Gutmann, one of the leading civilian cryptographers.

The *secure data deletion* process of srm goes like this:

- **\***

  1 pass with 0xff

- **\***

  5 random passes. /dev/urandom is used for a secure RNG if available.

- **\***

  27 passes with special values defined by Peter Gutmann.

- **\***

  5 random passes. /dev/urandom is used for a secure RNG if available.

- **\***

  Rename the file to a random value

- **\***

  Truncate the file

As an additional measure of security, the file is opened in O\_SYNC mode and after each pass an fsync() call is done. *srm* writes 32k blocks for the purpose of speed, filling buffers of disk caches to force them to flush and overwriting old data which belonged to the file.

## COMMANDLINE OPTIONS

- **-d**

  ignore the two special dot files . and .. on the commandline. (so you can execute it like "srm -d .\* \*")

- **-f**

  fast (and insecure mode): no /dev/urandom, no synchronize mode.

- **-l**

  lessens the security. Only two passes are written: one mode with 0xff and a final mode random values.

- **-l**

  \-l for a second time lessons the security even more: only one random pass is written.

- **-r**

  recursive mode, deletes all subdirectories.

- **-v**

  verbose mode

- **-z**

  wipes the last write with zeros instead of random data

## LIMITATIONS

- **NFS**

  Beware of NFS. You can't ensure you really completely wiped your data from the remote disks.

- **Raid**

  Raid Systems use stripped disks and have got large caches. It's hard to wipe them.

- **swap, /tmp, etc.**

  Some of your data might have a temporary (deleted) copy somewhere on the disk. You should use *sfill* which comes with the *secure\_deletion package* to ensure to wipe also the free diskspace. However, If already a small file acquired a block with your precious data, no tool known to me can help you here. For a secure deletion of the swap space *sswap* is available.

## BUGS

No bugs. There was never a bug in the secure\_deletion package (in contrast to my other tools, whew, good luck ;-) Send me any that you find.  Patches are nice too :)

## AUTHOR

van Hauser / THC *\<vh@thc.org\>*

## DISTRIBUTION

The newest version of the *secure\_deletion package* can be obtained from  *http://www.thc.org*

*srm* and the *secure\_deletion package* is (C) 1997-2003 by van Hauser / THC (vh@thc.org)

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; Version 2.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

## SEE ALSO

*sfill* (1), *sswap* (1), *sdmem* (1)