Possible Cygwin setup regression with --prune-install

Shaddy Baddah lithium-cygwin@shaddybaddah.name
Thu Aug 29 08:08:00 GMT 2019

Hi Achim,

On 29/8/19 4:02 pm, Achim Gratz wrote:
> Shaddy Baddah writes:
>>   -Y --prune-install Prune the installation to only the requested
>> packages
>> My reading of that is that this should defeat any packages from being
>> (automatically added). However, even with this option, the base packages
>> are still autoselected.
> I've originally implemented that option and the Base packages and
> dependencies are explicitly exempted.  This is not an option to allow
> you to create broken installations, mind you.

But it's not an installation really. The only potential "breakage" that
I could see is that the attempt to create desktop icons would break.

But there's nothing to "postinstall", so having no shell, no anything
isn't an issue.

OK, I should expand a bit, to give some better understanding. For more
than a decade, I have employed an installation technique I'll call an
alternative root. See this for example:


The setup allows me to have an install of Cygwin on a host system, and
reuse that in a guest VM, over the VM implementations shared FS. Much
like the concept of a "zone" in Unix, I setup in the guest an
alternative root, with its own etc, var, etc.. and of course fstab
for a /tmp away from the one with the limitations of the VM shared FS.

Before Cygwin 1.7, I achieved the alternative root through the registry
key. After Cygwin 1.7, I have maintained a local patch that works of an
environment variable to point at an "alternative root".

There are other non-VM applications to this too.

To bootstrap the "alternative root", I used to run setup as above. I
then could be sure that all the required directories under root were
created, with the right Windows ACL, etc.

I'd then fill in /etc, setup my launching batch file, and away I go.
It's worked very well for me for years.

I'd never expect the support of the list to continue this practice. I
just lament losing what I see as the "elegant" approach I had to
"bootstrap" the alternative root. I might look into maintaining another
local patch for Cygwin setup.

>> But can someone talk to what --prune-install is exactly supposed to do?
>> And can any consideration be given to a "skeleton/template" install?
> I use that option to make sure that whenever I remove packages from my
> install (or downgrade them), the clients pick the exact set of packages
> up that I give them.  It's also used to shrink installations (i.e. from
> a developer installation to user) without leaving lots of cruft behind.

Thank you for that. That is different to what I expected. And I can see
good uses for this option.


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