Re: Feature request

* Morten Nilsen
| The tinysofa distro replaced swup with apt in the enterprise version,
| and one of the reasons listed, was that apt didn't download anything if
| nothing was new... ie. it checked the timestamp of it's "latest.rdf"
| before downloading it..

SWUP does grab latest.rdf.md5 which is 45 bytes.  For that, it gets a
way of verifying with 100% (ok, not 100% but so close it is hardly worth
mentioning) certainity whether the latest.rdf has been updated or not.

This way is 100% indipendent on:
* Timestamps (yes, these can vary, think timezones and software used to
  mirror for starters)
* Protocol used (you can use the same method whether it is a local file,
  cdrom, FTP, HTTP, NFS and whatever else you can think of).
* Any other external matters (I am sure someone with your creativity can
  think of some)

It also does not really cost you any more than a check of the timestamp.

If we assume protocol FTP, the cost is the same except for that SWUP does
unconditionally grab 45 bytes while apt gets
-rw-r--r--  1 501  100       224993   Oct  7 14:56   latest.rdf
aka 64 bytes.

If we assume HTTP, you get an additional 45 bytes or so if using SWUP.


So to sum it up:
* SWUP has a 100% certain way of getting this right with the same
    implementation for all protocols and media.
* APT does not as it relies on the media (yes, I know you usually don't
    swap mirrors that often) and has to make special exceptions if the
    file comes in via FTP, HTTP or whatever else.

The cost of the two is within 100 bytes of each other.

If this was the real reason for the tinysofa swap, I consider it based on
bad research.


| I think swup should do this as well, and only get the latest.rdf if it
| is newer than the one in the cache.

This was thought of in the original design of SWUP and the solution still
used today was considered supreme.


| Morten


Erlend..
-- 
Erlend Midttun                                            [email protected]
Head of Trustix Secure Linux Department, Comodo Group  http://www.trustix.org/
IRC: Golle                                         Registered Linux user #5779
                  Where do you want to fly today?  Linux.