Backup Levels

The UNIX world has adopted the concept of numeric backup levels to describe which files are being saved in a given backup.

Level	Meaning
0	Full backup of all files.
1	Backup of all files modified since the last time a level 0 backup was performed.
2	Backup of all files modified since the most recent level 1 backup.

At some point in your life, your computer will crash, and you will lose all the data on it. Whether this is a temporary inconvenience or the first step down the road to suicide is entirely dependent on your level of preparation. Right now, right this second, you should think about what you have on your machine that you can't afford to lose. Is it being backed up? If not, go do something about it.

Once you've settled on a backup strategy, you can automate most of it with cron. All you'll have to do is switch out the tapes (or whatever means you use to backup) every so often.

Though it is technically possible to use the archiving commands in this section as a normal user, for the most part you're going to be running them as root.

The commands covered in this chapter include the following:

`compress`	Compress file with Lempel-Ziv encoding
`cpio`	Archive files
`dump`	Save an entire filesystem
`gzexe`	Compress an executable file in place
`gzip`	Compress a file
`gunzip`	Uncompress a gzipped file
`restore`	Restore filesystem saved with dump
`shar`	Create a shell archive
`tar`	Pack and unpack archive files.
`uncompress`	Expand compressed file
`uuencode`	Encode a file for mail transmission
`uudecode`	Decode a file encoded with uuencode
`zcmp`	Compare two zipped files
`zdiff`	Compare two zipped files
`zgrep`	Search the contents of zipped file(s)
`zmore`	Display the contents of zipped file(s)
`znew`	Convert from compress format to zip format