Linux System Administration Recipes A Problem-Solution Approach

CHAPTER 4 ■ TAKING BACKUPS AND MANAGING DATAThis will treat the source image (using the -s option, which here is hdaimage.dd) as an ext3 filesystem (set withthe -f option). -C specifies the config file, and -d specifies the directory to output to. If you add the -h option,thumbnails of the image files will also be created. There are other config (rules) files supplied, or you can writeyour own.4-13. Securely Wiping DataIt’s quite common to find yourself replacing machines that are still functional but don’t match up to thespecs you now need. These days, a three-year practical life span is about the best case in mostenvironments, but a three-year-old computer should still be perfectly functional. Ideally, therefore, youshould give them a new home rather than just throwing them out. Take a look for charities or recyclingorganizations in your area, or even offer them around to your staff!However, before you send the machines off to begin their new life, you need to consider datasecurity. Just deleting old data isn’t enough. It’s possible, if you know what you’re doing, to retrievedeleted data from the disk.DBAN (which stands for Darik’s Boot And Nuke), available from http://www.dban.org/, is designedto fully and securely wipe your disk. It’s a downloadable self-contained boot disk, available for CD/DVD,floppy disk, or USB flash drive. Boot from it, and it will look for hard disks on the system and then giveyou the option of deleting any or all of them by just hitting Enter.■ Note For RAID arrays, you may need to manually disassemble the array first.Several wipe methods are available, from a quick erase to a full three-pass wipe, including a coupleof methods that are used by the U.S. Department of Defense! The autonuke option, which is the defaultfrom the first screen, will automatically run through all detected disks, securely wiping them, so becareful with it, and make sure that you really are done with the machine before you start.■ Note A full standard disk wipe, especially on an old or slow machine, can take a long time (three to four hoursis quoted as standard, but it can be much more than that on older machines). I usually leave it running overnight.DBAN is easy to use and very secure; it uses multiple methods (including the Gutmann method andthe Mersenne twister) to ensure that the data really is gone for good. It’s a handy program to keeparound on disk, but make sure you label it very clearly and don’t end up booting from it by accident! (Itwon’t run without input, but it’s still best to be careful with anything seriously destructive.)118Download at WoweBook.Com