Testing changes in FAI

[Michael Tautschnig]

[...]
> 
> Is there currently a way to answering the question "What would FAI
> do?" for a given host *other* than actually FAI'ing that host?
> 
Not that I would know of. However, many of us here would like to see that in FAI
:-)))

> I'm thinking of some kind of script which would recurse through the
> config hierarchy and evaluate files and scripts to determine things
> like:
> 
>  - which classes a given host is in
I think you will need to run this test on the acutal machine because the classes
usually depend on the software/hardware configuration of the machine being
installed. However, these scripts usually should not touch anything, just
read-only access.

>  - which scripts would run and what the output/results of those
>    scripts would be
Which scripts are you talking about? Those in class/ or those in scripts/?

>  - which disk config would be used
Ok, that's quite easy once you know which classes are there.

>  - what files would be installed (via fcopy)
fcopy now has an option --dry-run (probably available in 2.10.x), it might be
helpful (alternatively the environment variable FCOPY_DRYRUN may be set).

>  - what packages would be installed (and what dependencies would get
>    dragged in)
This will probably demand a patch to install_packages, but it seems feasible.

> 
> In theory, this script could be given a hostname of some machine and
> run this test as if it were that host doing the actual FAI install.
> Sort of a lint for FAI type of thing.
> 
> Obviously, since that host would not actually be installing, this
> script would not be able to actually do certain things like partition
> disks, fcopy files, and install packages.  But it could certain
> provide a significant amount testing to any given configuration change
> and inform you whether or not the change would result in the desired
> outcome when you do actually go and install the host.
> 
> The FAI softupdate feature seems like it might be a good place to
> start, but appears to have to actually run on the host.
>
I don't think fai softupdate is the way to go, because that will just mean that
you skip some tasks, such as partitioning. I'd rather go for a new method (like
dirinst, which has recently been added), something like

fai test

That will definitely require some work on FAI, but it would still seem very very
helpful, especially for the developers. To this end I suggest adding something
similar to --dry-run/FCOPY_DRYRUN to all relevant scripts; then simply exporting
FCOPY_DRYRUN (and maybe INSTALLPACKAGES_DRYRUN and the like) from /usr/sbin/fai
would already do quite a bit of the job.

Regards,
Michael




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