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Date: Fri, 3 Sep 2004 11:41:27 +1000 (EST)
From: luke DOT kendall AT cisra DOT canon DOT com DOT au
Subject: How to detect a broken Cygwin mirror?
To: cygwin AT cygwin DOT com
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Message-Id: <20040903014127.6FBDC8454B@pessard.research.canon.com.au>

Is there a scriptable way (on the Unix host, or under a working Cygwin
install), for us to detect a faulty mirror?  The mirrors seem to cause
problems very regularly.  This is about the 3rd one we've tried.

SysAdmin here are coming to object to Cygwin - they say they get only  
slightly fewer support requests for Cygwin than they do for Exchange. 
*Usually* they can solve the problem. They only call me in for hairier
problems (like this "incomplete download" that was affecting another
user here, which lead me to my current sad adventure).

Normally they and I together can sort out the issue when they need extra
Cygwin-specific expertise, and move on.  The worst experiences, in my
opinion, are like this one, that seem to come down to a broken mirror:
our mirror rsyncing to it and breaking, and then people updating or
installing from our broken mirror, and getting into states like my PC is
in now.

They also say it's common for it to be very, very hard to remove
C:\cygwin - unable to remove it, unable to take ownership, on occasion
having to boot into safe mode to get rid of it (on the way to trying a
fresh Cygwin install, you see).

We're about to pick another random rsync mirror, other than kernel.org,
and try again.  It would be nice to find out if the mirror was corrupt
before starting the 2GB download though, rather than after.

Could the uploads perhaps start by removing a flag file called, say,
"mirror-is-correct", upload files checking that they transferred
correctly, then write the file "mirror-is-correct" afterwards?
Personally, I can't see a way to do that with existing tools (ftp,
rsync), since you'd need to run md5 on the foreign system. :-(

Failing that, is there something we can run on the Unix host to check
that our mirror is correct?  Can we perform the same md5sum check that
setup does?

Any advice?  Even just a suggestion of an rsync mirror that is
currently known to be good, and which has moderately good bandwidth?

Thanks,

luke


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