[Yum] Questions about headers ...

[Robert G. Brown]

On Wed, 24 Sep 2003, C.Lee Taylor wrote:

> Greetings ...
> 
>     Got a few questions, hope that they make sense ...
> 
>     First, is there a way to "package" the headers, so that I don't have 
> to wait almost an hour to do my first "yum check-update"? I could also 
> save a little bandwidth if I could put the basic headers in place before 
> an update ...

This has been suggested before, and of course you can do it by hand, but
bandwidth is bandwidth and once the headers have been created/compressed
all you're really saving is the per-transfer overhead, not the bandwidth
per se.

>     Another question, would it not be better to just download the 
> headers for the packages install on a PC that one would be doing an 
> update on?

This won't work.  yum checks across ALL packages for dependencies and
conflicts.  This is fairly complex, as a package may need another
package or be needed BY another package, all recursively, until all
dependencies are resolved.  So it isn't possible to predict ahead of
time which package headers are needed.  One reason that yum functions so
fast is BECAUSE it has a local copy of all of the headers.

>     I ask these question, because bandwidth in South Africa is like 
> water in Mexico ( please don't flame me, it just sound poetic ), 
> expensive and hard to find quality ... if there are anyways to reduce 
> bandwidth requirments I am all ears ... and I am sure that the mirrors 
> and hosts for yum repo's would welcome any help as well ...

The best way is to create a local repository (usually by mirroring an
existing repository).  This costs you a whole lot of bandwidth -- once
-- to set up the repository, and then you use LOCAL bandwidth in your
LAN to do all the updates and whatever.

The rsync tool can be used to create the mirror, and then used
periodically thereafter to refresh the mirror.  rsync is totally minimal
in its use of bandwidth -- it can be set to only send files that have
changed, to compress all files before sending them, to ignore files that
you don't want.  So you can actually construct an rsync command that
mirrors only SELECTED PARTS of a repository elsewhere initially, and
then only updates those parts if and only if the files have been updated
on the original repository you are mirroring.

I have a DSL link into my home, and DSL is slow as molasses (384 Kbps
inbound, on a good day).  I have a bunch of hosts at home to yum install
or yum update.  Disk, on the other hand, is absurdly cheap and
plentiful.  So I mirror the repository(s) at Duke via rsync onto my home
server.  The first time this was immensely painful -- it took something
like a day to complete the mirror.  However now when I rerun the rsync
script it updates in a matter of seconds (if there is nothing new to
download) to minutes (if a half-dozen rpm's have been updated in the
meantime).

   HTH,

     rgb

> 
> Thanks
> Mailed
> Lee
> 
> 
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-- 
Robert G. Brown	                       http://www.phy.duke.edu/~rgb/
Duke University Dept. of Physics, Box 90305
Durham, N.C. 27708-0305
Phone: 1-919-660-2567  Fax: 919-660-2525     email:rgb at phy.duke.edu