wipealldisks Should Be More Secure

[billglick]

https://github.com/ncsa/xcat-tools/blob/b62263896929ba1f8effa9a1c46a27a05985f7d5/extras/wipealldisks#L30

Should probably use random data instead of zeros in the dd command:

"if=dev/urandom"

May also want option to apply this multiple times. Historically campus policy was to overwrite the disk 3 or more times with random data.

https://answers.uillinois.edu/illinois/page.php?id=69861 says the following about how scrubs/overwrites should happen:

Q. What do you mean by "scrub" or "overwrite"? A. On spinning-platter and magnetic type hard drives, scrubbing or overwriting means writing over each bit with random ones and zeroes. For flash memory and SSDs a different approach must be taken because it operates differently than magnetic media. Most SSDs have special data purge commands built into their hardware. These should overwrite the data in multiple passes using a pattern in the first pass and a complement in the second pass.

[billglick]

This is probably not at all urgent.

But another option could be to use ATA Secure Erase functionality. See:

• https://superuser.com/a/1284465
• https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase
• https://www.thomas-krenn.com/en/wiki/Perform_a_SSD_Secure_Erase