Re: Feature request

(Oct 15 2004 12:28) Morten Nilsen wrote:
> here is the text I read pertaining to swup/apt, it also talks of yum:
> 
> Omar Kilani wrote:
> > APT provides a stable, secure, well tested, easy to use, and
> > completely extensible package management system. It has been in use
> > by Debian since 1998, cryptographically checks repository meta data
> > and packages for authenticity, is simple to use and is fully
> > extensible via the lua scripting language (which is simple enough for
> > anyone to write their own package management functionality with.)

Swup has done "cryptographically checks" since its beginning.

I have not looked into lua, but think that most people don't need to
extend swup and that if they do python is easy enough.

> > The advantages of APT over existing package management tools are
> > numerous. Apart from the above mentioned features, the stability and
> > speed of APT's network access methods are unmatched by any of the
> > currently available Python based package management tools.

Marketing buzz, nothing said so far has any substance.

> > Additionally, the way in which APT handles repository meta data is,
> > in my view, far superior to the "header caching" that is utilized by
> > YUM/SWUP/etc. A "one compressed file per repository" approach makes
> > more sense in the majority of cases than a "one file for every
> > repository, file, package and resource" approach.

The 1 file thing is something we have been considering for at least
parts of swups repository information. But not all. It's a tradeoff that
each package management system has to make. All in one file makes for
more download when you install single packages and updates, but for less
when you do a full install from scratch.

We choose to spli things up because normally you don't upgrade / install
hundreds of packages at the same time on a production system.

> > To demonstrate this point, one can compare an update/upgrade with yum
> > to an update/upgrade done with apt. If one wanted to install package
> > 'foo' with yum, they would issue the 'yum install foo', command. Yum
> > then proceeds to download 8 megabytes of seemingly irrelevant headers
> > (it's network access routines failing over from one site to another
> > every few headers), and finally retrieves the foo package and it's
> > dependencies, and installs them. In comparison, apt downloads a 600KB
> > compressed file that describes the whole distribution tree, and then
> > simultaneously downloads foo and all it's dependencies. Re-running
> > the exact command used (yum install foo) somehow results in more
> > irrelevant headers being downloaded, one at a time, and then a
> > message stating that package foo is already installed. apt, on the
> > other hand, instantly displays the same message.

Omar switched to apt from swup because apt is better than yum? Sounds
strange.. :)

> > A transfer test comparing apt, swup and yum in a "there have been no
> > updates" scenario with the same package repository, shows apt
> > transferring 686 bytes, swup transferring 25 kilobytes, and yum
> > transferring 10 kilobytes.

This is completely untrue.

I just did a test and on a normal "Your system is up to date" swup
dowloads 45 bytes per site. This is the size of the md5sum file of
latest.rdf

If the repository is completely empty, as in after a swup --flush-cache,
a normal trustix site gives:

-rw-r--r--    1 root     root           45 Oct  7 14:56 latest.rdf.md5
-rw-r--r--    1 root     root        16851 Oct  7 14:56 latest.rdf.gz
-rw-r--r--    1 root     root          189 Oct  7 14:57 latest.rdf.asc

Which calculates to 17085 bytes or 16.7 KB

So even with a completely empty cache Omars numbers are silly. In any
normal situation you have the latest.rdf downloaded already.

The REALLY interesting numbers is what 'atp-get update' downloads into
an empty repository.... :)

> > One final "killer feature" of apt is the ability to use a CD ROM as a
> > package repository, automatically handling mounting and un-mounting
> > of media, as well as treating the CD ROM source preferentially to
> > remote sources.

Swup cope with CDROMs as with anything else. It has supported this since
the early beginning. You just need to manually mount and unmount the CDROM.

Automatically handling mounting and unmounting is of course a feature.
But if I'm not mistaken Omar is fighting to keep Tinysofa small enough
to fit 1 -one- CD. 

The only time this feature is interesting is:

1. you don't have network access
2. you have all the CDs needed, and they are up to date

Since we are not even remotely close to use a full CD this feature is
not that interesting.


I don't know why Omar wanted to switch from swup. It may be that we
wanted to differentiate Tinysofa from Trustix, or something similar. But
to suggest that apt is better in general than swup when it comes to act
as the everyday package manager is silly.


kind regards


c


-- 
Christian H. Toldnes
Trustix Developer

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