Chapter 23. Archiving and Compression
Chapter 23. Archiving and Compression
Introduction
Backup Levels
Related Files
Commands
Introduction
The commands in this section deal with the compression, storage, and extraction of system files. Typically, you'll want to compress and store at the same time—no need to take up 200M of storage space when 100M will do.
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| One of the biggest differences between a professional systems administrator and some incompetent who |
A full backup saves every file within some specified set. An incremental backup backs up only those files that have been changed since the previous backup. The idea behind making incremental backups is that the bulk of the files on the system never change, so it's unnecessarily expensive in terms of time and disk space to keep copying them over and over. The downside is that when you're mixing full and incremental
Of the compression utilities listed here, the two most popular are probably compress and gzip. Compress (.Z file extension) used to go out with all UNIX distributions, so you see it around a lot. Gzip (.gz file extension) is more efficient and happens to have fewer license restrictions, so it's probably the best choice for day-to-day work.
Backup Levels
The UNIX world has adopted the concept of numeric backup levels to describe which files are being saved in a given backup.
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Level |
Meaning |
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Full backup of all files. |
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1 |
Backup of all files modified since the last time a level 0 backup was performed. |
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2 |
Backup of all files modified since the most recent level 1 backup. |
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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
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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. |
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Though it is technically possible to use the archiving commands in this section as a normal
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The commands covered in this chapter include the following:
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compress |
Compress file with Lempel-Ziv encoding |
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cpio |
Archive files |
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dump |
Save an entire filesystem |
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gzexe |
Compress an executable file in place |
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gzip |
Compress a file |
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gunzip |
Uncompress a
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restore |
Restore filesystem saved with dump |
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shar |
Create a shell archive |
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tar |
Pack and unpack archive files. |
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uncompress |
Expand compressed file |
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uuencode |
Encode a file for mail transmission |
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Decode a file encoded with uuencode |
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zcmp |
Compare two
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zdiff |
Compare two zipped files |
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zgrep |
Search the contents of zipped file(s) |
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Display the contents of zipped file(s) |
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znew |
Convert from compress format to zip format |
Related Files
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/dev/rmt* |
Default tape unit to dump to |
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/etc/dumpdates |
Dump date records |
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/etc/fstab |
Dump table, file systems, and frequency |
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/etc/
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To find group operator |