NOTE: If you have data that is important to you, you should have a known backup.

Accidents and oversights happen. Tapes can be damaged, lost, or mislabeled. Assume that your system administrator is top-notch. The best administrator can recover your lost data 99 percent of the time. There is still a small chance that the files you need might not be recovered. Can you afford to duplicate months of effort 1 percent of the time? No.

An experienced user learns to be pessimistic. Typically, this important perspective is learned the hard way. Perhaps a few hours are lost. Perhaps days. Sometimes months are lost.

Here are some common situations:

• A user works on a file all day. At the end of the day, the file is deleted by accident. The system manager cannot recover the file. A day's work has been lost.

• A programmer tries to clean up a project directory. Instead of typing rm *.o the programmer types rm * .o and the entire directory is lost.

• A user deletes a file by accident. After a few days, the user asks the system administrator to recover the file. The incremental backup system has reused the only tape the missing file was on.

• A large project is archived on a magnetic tape and deleted from the disk. A year later, some of the information is needed. The tape has a bad block at the beginning. The system manager must learn how to recover data from a bad tape. The attempt is often unsuccessful. The information is lost forever, and must be re-created at the cost of months of effort.

• Someone breaks into a computer and alters or deletes crucial information.

• A fire breaks out in the computer room. The disks and all of the backup tapes are lost.

Gulp! I scared myself. Excuse me for a few minutes while I load a tape...

Ah! I feel better now. As I was saying, being pessimistic has its advantages.

Making a backup is easy. Get a blank tape and put a label on it. Learn how to load it into the tape drive. Then do the following:

% cd
% tar c .

Take the tape out. Write-protect the tape (usually, just slide the tab). That's all.

[Well, okay, not exactly. That would back up only your home directory to the default tape device (usually something like /dev/rmt0). You may want to back up more than just your home directory, the tape drive may not be at the default device, and you may not have permission to write to the tape drive by default. The rest of the chapter talks about variations on the theme. -- DJPH]

-- BB

38.2. tar in a Nutshell		38.4. More Ways to Back Up