4.16. Removing Data Securely Using scrub
The scrub utility sets patterns on special files or disk devices to make retrieving data more difficult. Using scrub is faster than writing random data on a disk. This process provides high availability, reliability, and data protection.
To start using the
scrub command, install the scrub package:
~]# yum install scrub
The scrub utility operates in one of the following basic modes:
-
Character or Block Device - The special file corresponding to a whole disk is scrubbed and all data on it, is destroyed. This is the most effective method.
scrub[OPTIONS] special file -
File - A regular file is scrubbed and only the data in the file is destroyed.
scrub[OPTIONS] file -
Directory - With the
-Xoption, a directory is created and filled with files until the file system is full. Then, the files are scrubbed as in file mode.scrub-X[OPTIONS] directory
Example 4.7. Scrubbing a Raw Device
To scrub a raw device /dev/sdf1 with default National Nuclear Security Administration (NNSA) patterns, enter the following command:
~]# scrub /dev/sdf1
scrub: using NNSA NAP-14.1-C patterns
scrub: please verify that device size below is correct!
scrub: scrubbing /dev/sdf1 1995650048 bytes (~1GB)
scrub: random |................................................|
scrub: random |................................................|
scrub: 0x00 |................................................|
scrub: verify |................................................|
Example 4.8. Scrubbing a File
- Create a 1MB file:
~]$
base64/dev/urandom | head -c $[ 1024*1024 ] > file.txt - Show the file size:
~]$
ls -lhtotal 1.0M -rw-rw-r--. 1 username username 1.0M Sep 8 15:23 file.txt - Show the contents of the file:
~]$
headfile.txt JnNpaTEveB/IYsbM9lhuJdw+0jKhwCIBUsxLXLAyB8uItotUlNHKKUeS/7bCRKDogEP+yJm8VQkL-1 - Scrub the file:
~]$
scrubfile.txt scrub: using NNSA NAP-14.1-C patterns scrub: scrubbing file.txt 1048576 bytes (~1024KB) scrub: random |................................................| scrub: random |................................................| scrub: 0x00 |................................................| scrub: verify |................................................| - Verify that the file contents have been scrubbed:
~]$ cat file.txt SCRUBBED!
- Verify that the file size remains the same:
~]$
ls -lhtotal 1.0M -rw-rw-r--. 1 username username 1.0M Sep 8 15:24 file.txt
For more information on
scrub modes, options, methods, and caveats, see the scrub(1) man page.
