Archiving and Compression

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Chapter 8 from Scott Granneman's new book "Linux Phrasebook", the pocket guide every linux user needs. Linux Phrasebook offers a concise reference that, like a language phrasebook, can be used "in the street." The book goes straight to practical Linux uses, providing immediate solutions for day-to-day tasks.
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Unzipping Password Protected Zips

Anonymous's picture

You left out how to unzip ZIP files that are password protected in Linux. I'm searching for this elusive bit of information on the internet right now...

Password protectedly adding files by PHP code was not found

Farrukh Shahzad's picture

Password protectedly adding files by PHP code was not found on the internet when i was searching for it... so i come across your article and it gave me the idea to why not issue a system command by php to add files in zip and even protect the files by password ;)

RAR

Amelia's picture

RAR is good and free too. It supports passwords and can make SFX archives.

No mention of lzma?

Brian Cain's picture

How about rzip or lzma? I recall an article in the print edition within the last ten or eleven issues that compared the cpu overhead of each compression method against compression ratios (and possibly other parameters). Anyways, rzip is memory and cpu intensive, IIRC, but has the potential to make enormous savings. I think it's the same as burrows-wheeler over larger data sets, possibly. Worthwhile for stuff that won't be frequently decompressed, IMO.

rzip

Anonymous's picture

actually rzip levels are in search buffer sizes:

-0 = 100MB
-1 = 100MB
-x = x00MB for x>0 and x<=9

cpu intensive? well depends. I hacked bzip2 compression hooks out of the rzip and it's one of the fastest pre archiving filters with best compression ratio for mysql dump of dbmail database.

yup found bug but only in decompression algorithm - not the data itself. yes - made Andrew to fix it.

Correction to wording

DAKH's picture

Scott,

In the section "Archive Files with tar", paragraph 3, you state that tar is "designed to compress entire directory structures". I think this should read "designed to archive...", since this section deals only with tar's standalone use as an archival tool and since this article/chapter is intended to highlight the difference between archiving and compressing. Other than that, this is a very handy primer on archiving and compressing in *nix.

bzip2 -9

Chris Thompson's picture

The article states that the default block size for bzip2 is -6. The man page for my system (Ubuntu 6.06) states that -9 is the default, and I am unaware of any system where -6 is the default.

TROGDOR STRIKES AGAIN!

TROGDOR's picture

Making -9 the default

Craig Buchek's picture

An easier way to default to the best (-9) compression level would be to export GZIP='-9' and ZIPOPTS='-9' into your environment.

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