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Complete Idiot's Guide to Linux
(Publisher: Macmillan Computer Publishing)
Author(s): Manuel Ricart
ISBN: 078971826x
Publication Date: 12/22/98

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Chapter 19
Backups: Safeguarding Your Work

In This Chapter

  Media Are Just Devices
  What to Back Up
  Simple Backups
  Tape Archive: tar
  A Backup Strategy
  Graphical Backup Programs

Without a doubt the most important maintenance task that you can perform on any computer is a backup. Backups can be tedious tasks, but it’s usually when you have neglected to do it that you most need it! Having a backup for your data can mean the difference between an inconvenience and a catastrophe. Without a backup, you’ll have a dé já vu experience recreating the work you lose. As you might already know, that is no fun. Restoring your system from a backup can be an inconvenience, and maybe a few hours of work will be lost, but it is much different than losing work you’ve created throughout past weeks, months, or even years!

A backup might be required even for simple user errors such as deleting important files. Unlike Windows or other operating systems, under UNIX/Linux there’s no “undelete” program, Norton Undelete, or any other tool to restore deleted files. If the file is deleted, it is gone. The reason these utilities don’t exist for UNIX/Linux is the way that disk space is allocated: When you delete a file and release its storage space, this space will probably be written over next. So even if such tools existed, it is likely that they would be useless. Your only guarantee of getting a file back is to have a backup.

Although backing up is not difficult, it can be tedious and time-consuming. However, you should consider it an essential task and time investment. To put it in perspective, some backup is better than none at all. How often you should do it will depend on many issues. The answer is that it depends. A server that constantly has new information on it needs to be backed up more often than a standalone user workstation that rarely changes. If your system acts as a file server on which users or other programs store data, all bets are off. You don’t have the luxury of determining what is a good interval; you should back it up daily.

On a multiuser system such as Linux, proper backup is even more important. A crashing disk could take away the work of many, potentially hundreds of, users. Losing other people’s work is a good way to have a lot of people mad at you! Regardless of the type of system you have, you’ll need to back up the data. Linux can make it easier than you thought, provided you have the right equipment.

Your backup hardware needs might be as simple as floppy disks or tape media, or as complicated as requiring specialized hardware that maintains redundant systems in which a secondary disk is ready and waiting to transparently take the place of the failed one. This chapter covers simple backups. Specialized hardware is better administered by an experienced administrator. In terms of media, you can use floppies, although in the long run tapes are much more reliable, and in turn some optical media might be more reliable than a tape. How reliable information is will depend on the length of time that you’ll need to keep data around.

To see a list of compatible tape drives, see Appendix B, “OpenLinux Compatibility Guide.”

Media Are Just Devices

The programs you can use for backing up under UNIX/Linux have been around for a long time and are very stable. None of these programs rely on a particular piece of hardware to perform their function and can all work equally well outputting their data to a floppy, a tape, any kind of disk, or a file. The file used for a backup is often just the device (/dev) file where you point your backup to go.

How you handle your backup strategy is really a matter of personal preference. If you establish policies, such as describing what you back up, it becomes easier to do many system administration tasks. Also, it is important to have the right hardware for making backups. By “right hardware” I mean that the disks you back up must fit onto a convenient backup medium; otherwise, you’ll have more tapes or disks than you’ll know what to do with. If you can afford it, buy a tape drive. This medium is inexpensive and can hold a lot of data. Other backup solutions might also work on your network, depending on how much data you need to back up.


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