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Linux: A Network Solution for Your Office ContentsIndex Chapter 17: Backups: Backup Strategies Previous ChapterNext Chapter Sections in this Chapter: Backup Strategies Advanced Topics Backing Up Files Summary The Tools of Backup Manual Pages Previous SectionNext Section Chapter 17 Backups You've heard it enough from system gurus: Always have an up-to-date backup of all data on your computer! When it comes to servers, maintaining backups is even more important; if the system goes down and data is lost, many users might be affected. But what, exactly, is a meaningful backup strategy for a Linux server? And on the practical side, what's the best way to create backups? Backup Strategies Backing Up Is Not Enough Planning for Restores Creating a backup should be simple, right? All you need to do is to make a copy of all the files on the hard drives of your system. Then, when disaster strikes, you simply restore the files from backup, and--Presto!--everything is ready to go. Or is it? Backing Up Is Not Enough The trouble with this simplistic backup strategy is that although it does ensure that all your data has backup copies, it fails to take into account the procedure of restoring the data. Consider the following example: You've created a full backup to tape using the Linux tar command (we'll talk more about this command later) on a tape drive you purchased recently at an auction, and this tape drive has been giving you trouble-free service ever since. A compressed, encrypted archive is stored on a tape that, for added safety, you decided to store offsite. Then, one morning, you enter your office, only to find that your Linux machine has been stolen or destroyed by a short circuit in its power supply. What now? Obtaining another machine should present no great difficulty, especially considering that a Linux server that's not heavily loaded runs on just about everything that deserves to be called a computer these days. Getting a hold of your dad's old 486 is not a problem, but it's not going to solve your dilemma. The first puzzle you'll face will be fairly obvious as soon as you notice the lack of a suitable receptacle into which your backup tape, just retrieved from off-site storage, would be inserted. Ouch! So, you spend the next 24 hours in a mad search for a compatible tape drive. If you're lucky, you at least know the model number. Later, you eventually find an online surplus store on the Internet that's willing to ship you the correct unit, at a huge markup, from a warehouse somewhere in Alaska or Hawaii. Eventually the unit arrives; you install it and turn on the system. You're greeted with the prompt of an obsolete DOS version still on dad's computer, and you have no clue as to how your perfectly functional Linux system can be retrieved from your tape. DOS has no tar command, nor does it recognize tape drives without third-party software. Eventually, you realize that in order to run tar to read your tape, you must have a working copy of Linux first, and so you proceed with the installation of a fresh copy. You install a minimum system, access the tape, find to your delight that the tape is perfectly readable, and start the process of restoring files. When you're finished, you attempt reboot the system; however, the system fails to boot. After some head-scratching, you realize why: The system you just brought back from the tape is incompatible with your dad's old hardware. So, you proceed with a fresh Linux installation, setting up a more complete system this time, and then you begin the painful process of restoring files and directories selectively. You take great care to ensure that you restore your critical data and system settings but that you don't overwrite the new operating system configuration, which would render Linux unbootable on this computer. How many hours, how many days have passed? How long was your Web site unavailable, your colleagues without email, your office without an Internet connection? All these problems could have been avoided, of course, if instead of following a textbook backup strategy, you had planned for restoring your system. Planning for Restores The term backup strategy is a misnomer. Anyone should be able to issue a tar command to copy his system's contents to tape or use one of those fancy window-based backup programs that are so fashionable these days. Rotating tapes and doing backups on a scheduled basis is not much of a strategy. No, the real planning should be about what to do after disaster has struck. How are you going to bring the system back online with backup hardware? What files should be backed up in the first place? What hardware should you use for backup purposes? Chapter 22, "Moving to Backup Hardware," tells you what needs to be done when your Linux system fails and it's necessary to install a backup system. The focus of this chapter is on creating suitable backups that will make your job easier as well as on recovery from less severe failures. Linux: A Network Solution for Your Office ContentsIndex Chapter 17: Backups: Backup Strategies Previous ChapterNext Chapter Sections in this Chapter: Backup Strategies Advanced Topics Backing Up Files Summary The Tools of Backup Manual Pages Previous SectionNext Section © Copyright Macmillan USA. All rights reserved. |