4.16. Removing Data Securely Using scrub
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: 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. File A regular file is scrubbed and only the data in the file is destroyed. Directory With the -X option, a directory is created and filled with files until the file system is full. Then, the files are scrubbed as in file mode. 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: Example 4.8. Scrubbing a File Create a 1MB file: Show the file size: Show the contents of the file: Scrub the file: Verify that the file contents have been scrubbed: Verify that the file size remains the same: For more information on scrub modes, options, methods, and caveats, see the scrub (1) man page.
~]# yum install scrub scrub [OPTIONS] special file scrub [OPTIONS] file scrub -X [OPTIONS] directory ~]# 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 |................................................| ~]USD base64 /dev/urandom | head -c USD[ 1024*1024 ] > file.txt ~]USD ls -lh total 1.0M -rw-rw-r--. 1 username username 1.0M Sep 8 15:23 file.txt ~]USD head -1 file.txt JnNpaTEveB/IYsbM9lhuJdw+0jKhwCIBUsxLXLAyB8uItotUlNHKKUeS/7bCRKDogEP+yJm8VQkL ~]USD scrub file.txt scrub: using NNSA NAP-14.1-C patterns scrub: scrubbing file.txt 1048576 bytes (~1024KB) scrub: random |................................................| scrub: random |................................................| scrub: 0x00 |................................................| scrub: verify |................................................| ~]USD cat file.txt SCRUBBED! ~]USD ls -lh total 1.0M -rw-rw-r--. 1 username username 1.0M Sep 8 15:24 file.txt