Matt Randolph wrote:
Nick Rout wrote:
On Sat, 2005-08-13 at 09:36 -0400, Jerry McBride wrote:
On Saturday 13 August 2005 01:32 am, Nick Rout wrote:
On Sat, 2005-08-13 at 00:58 -0400, Jerry McBride wrote:
Anyone else here subscribe to the LINUX JOURNAL?
In the September issue there's a neat article titled tha same as the
subject line of this message.
The skinny is, there's some really nice file compressors out there
and I
never heard of two of them... Anyone else know about LZMA or 7ZA?
The two mentioned compression tools work pretty much like gzip.
You tar
up your files, pipe to the compression filter and then on to the
target
file. Below is a small example of what I've been seeing here at the
shack.
-rw-r--r-- 1 root root 12359680 Aug 12 23:57 backup.tar
-rw-r--r-- 1 root root 3536665 Aug 13 00:01 backup.tar.7z
-rw-r--r-- 1 root root 4438465 Aug 13 00:08 backup.tar.bz2
-rw-r--r-- 1 root root 4747637 Aug 13 00:03 backup.tar.gz
-rw-r--r-- 1 root root 2731412 Aug 13 00:10 backup.tar.lzma
-rw-r--r-- 1 root root 5125474 Aug 13 00:16 backup.tar.lzop
What you're seeing are the results of compressing /lib on my gentoo
powered laptop. I've not bothered with timing the processes as the
better
compression rates are at the cost of speed and memory usage. Not
good for
"while you wait" processing, but just plain perfect for backups and
what-have-you on servers... One side note, 7za does not record
user/group
info...
Are you saying it removes user/group info from the tar file?
Not "removed", it's never put there... :')
I'm sorry but how do you create a tar file without preserving the
usernames and permissions?
This may be a case of a different paradigm being used by 7-zip than
that used by traditional (*nix) compression tools. If my memory
serves me, the 7-zip format is very similar to the pkzip format in its
usage. By that I mean that one is not required to make a tarball
before compressing multiple files. The format allows you to skip the
tar step and make an archive consisting of whichever files and
directories you wish.
The problem, I'm guessing, is that the 7-zip archive format was
developed in the Windows world where users and groups and permissions
have no meaning (I think that has changed or is changing in the NT/XP
world, but I don't know and don't especially care). Hence, these
attributes aren't accomodated by this format. I assume the 7-zip
extractor program sets the user and group of the extracted files to
that of whomever extracts them.
What everyone has rightly pointed out, namely that you can make a
tarball and then compress that, is exactly right. That IS how one
would use 7-zip with a proper operating system.
The original poster most likely used the 7-zip archiver as a
stand-alone tool, rather than using it in conjunction with tar. This
is not altogether surprising as one typically compresses a directory
with a single tar command (and an implied pipe) rather than explicitly
piping the output of tar to the compression utility. Since there is
no --7-zip switch in tar, the OP couldn't simply 'tar -7cf
backup.tar.7zip lib/'. The OP probably simply 7-zipped his directory
without tarring it first and consequently ran into the limitations of
the archive format.
"-rw-r--r-- 1 root root 3536665 Aug 13 00:01 backup.tar.7z"
Oops! I should read more carefully.
--
"Pluralitas non est ponenda sine necessitate" - W. of O.
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