Software used to create copies (backups) of your data, in order to protect it from loss, theft, fire, acts of God, etc. etc.

If you are reading this, chances are you have a computer, with some stuff on it you would be sad if you lost. If you haven't already, you should get some backup software and a CD-RW or a cheap tape drive today, and make some backups. Preferably multiple sets, some of which you don't keep in the same place as the computer (i.e. safe deposit box, desk at work, etc). Trust me, you'll start doing this the first time you lose everything; why not start early?

There is an unfortunate variety of backup software, much of which is, for some reason, of really atrocious quality. Your ideal backup software should let you use whatever hardware you have to back things up on, and it should support what are called incremental backups.

What do I use? Retrospect.

Notes about unix:

dump and restore aren't all that great. For instance, their support of incremental backups is... well... atrocious. Also, for linux users, the linux/ext2 port of dump is of especially tenuous quality. Make sure you visit the dump section of sourceforge and pull the very latest build. And cross your fingers.

Most Unix and Unix-like systems come with an excellent pair of basic backup and restore utilities, known as dump(8) and restore(8).

dump keeps track of when you've backed up your filesystems and lets you do up to nine levels of full, differential, and incremental backups. You can back up your fs to any file, most usefully a tape drive or similar device. Besides filesystems, you can also back up directories or, in some case, individual files.

restore provides an interactive shell-like interface for restoring from dump backups. It permits you to select the files you want restored from a fs backup, or to restore the entire fs if you prefer.

The trouble with dump, and the reason that many sysadmins still use the comparably primitive tar(1) or cpio(1), is that dump expects to be run on an interactive tty. If it has an error it doesn't just exit with an error code; it waits for user input. This means that it isn't too easy to run out of cron or a shellscript. A bit of Expect can solve this, though.

Mr. Option: dump and restore are certainly basic tools, and are not aimed at a fully differential or fully incremental backup strategy, yes. They tend to be stronger at a leveled backup strategy, such as the Towers of Hanoi backup strategy which is in the manpages.

Still, the optimal backup strategy depends strongly on how much your data change, and the tradeoff of time vs. space.

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