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Archiving and Compression

Oct 23, 2006  By Scott Granneman
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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
Submitted by Anonymous (not verified) on Mon, 08/27/2007 - 21:29.

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
Submitted by Farrukh Shahzad (not verified) on Wed, 03/07/2007 - 06:53.

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
Submitted by Amelia (not verified) on Fri, 12/08/2006 - 03:31.

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

No mention of lzma?

Brian Cain's picture
Submitted by Brian Cain (not verified) on Sat, 10/28/2006 - 16:57.

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
Submitted by Anonymous (not verified) on Mon, 10/30/2006 - 04:13.

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
Submitted by DAKH (not verified) on Fri, 10/27/2006 - 16:06.

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
Submitted by Chris Thompson (not verified) on Fri, 10/27/2006 - 11:19.

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
Submitted by TROGDOR (not verified) on Fri, 10/27/2006 - 11:06.

TROGDOR STRIKES AGAIN!

http://news.bbc.co.uk/1/hi/england/cornwall/6088008.stm

Making -9 the default

Craig Buchek's picture
Submitted by Craig Buchek (not verified) on Wed, 10/25/2006 - 13:18.

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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