[Thinlinc-technical] Migrate configuration during ThinLinc upgrade

[Peter Astrand]

Hi, see comments inline:


On Thu, 10 Dec 2015, Rob De Langhe wrote:
> very nice to hear your appreciation about operational stability during upgrades !

Thanks :)


> You ask about personal preferences, so here is my strictly personal preference:
> - I hate defaults, when they are not visible : to my preference, all possible parameters should be listed in
> config files, with their default value commented or explicitly assigned; this way I know what parameters exist,
> and by seeing their default values I can appreciate how to use them ; this dates from my stone-age era of
> learning programming via declarative languages as Pascal (no surprises, all is declared and visible)

One problem with default values in comments is that you cannot really be 
sure if you are looking at a default, or some old/commented out value. For 
example, in sshd_config, you will can often find:

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no

In this case, you cannot really say anything about the default. This could 
simply be that someone has tested both values. It is possible to improve 
this with a special syntax such as:

# Default: ChallengeResponseAuthentication yes

But still not perfect. For example, consider the case when someone has 
done:

"perl -pi -e s|ChallengeResponseAuthentication yes|ChallengeResponseAuthentication no|g'"


> - so if an upgraded software suite has new parameters, or no longer supports old parameters, I can easily run a
> 'diff' between old and new config files to see the differences in parameters (their existence, as well as their
> values)
> 
> Therefor, to me the option is always highly preferred to have a upgrade install its new config files,
> backing-out my old config files (renaming, obviously), and then telling me explicitly what diffs its finds
> between the new and old config files so that I assess manually each and every parameter change.
> 
> -> new defaults
> -> new config will work with the new software
> -> all new params are visible
> -> I assess each and every parameter change

I see. We are currently not shipping a copy of the default 
configuration, but have a bug for this: 
https://www.cendio.com/bugzilla/show_bug.cgi?id=5750


Br, 
---
Peter Astrand		ThinLinc Chief Developer
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