Possible Cygwin setup regression with --prune-install

Possible Cygwin setup regression with --prune-install

[Shaddy Baddah]

Hi,

I have a use-case for Cygwin setup, which I admit will seem strange,
whereby I want it to do an "Install" with no packages selected at all.
ie., just setup a "skeleton" of a Cygwin install. I value it, because
based my own experience with the Cygwin setup code, it seems to
"bootstrap" the Cygwin root directory, using only the Win32api, without
a reliance of a Cygwin DLL at the early stage.

I note that the last Cygwin setup enhanced the handling of dependencies
greatly. I have nothing but praise for that change, setup is definitely
much more modern and stable now.

Previous to this change, I could achieve the "skeleton" install by
choosing the totally new Cygwin root to install to, and selecting "Keep"
so that no package were selected.

With the new setup, even if I select "Keep", with no packages selected,
the tight dependency checking will autoselect all the "base" packages,
after clicking next.

I don't even question that there would be a good rationale to this. But
I considered that since this is a very niche thing I do, I should
explore my own workaround. So I looked into the other command-line
options, and noticed this one:

  -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.

Admittedly, I didn't try this with Cygwin setup from before the
redesign, so it may not classify as a regression on the command-line
option.

But can someone talk to what --prune-install is exactly supposed to do?
And can any consideration be given to a "skeleton/template" install?

-- 
Regards,
Shaddy

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Re: Possible Cygwin setup regression with --prune-install

[Achim Gratz]

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 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.


Regards,
Achim.
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Re: Possible Cygwin setup regression with --prune-install

[Shaddy Baddah]

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:

https://sourceware.org/ml/cygwin/2009-07/msg00904.html

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.

-- 
Regards,
Shaddy

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Re: Possible Cygwin setup regression with --prune-install

[szgyg]

On 2019-08-29, Shaddy Baddah wrote:
> I have a use-case for Cygwin setup, which I admit will seem strange,
> whereby I want it to do an "Install" with no packages selected at all.
> ie., just setup a "skeleton" of a Cygwin install. I value it, because
> based my own experience with the Cygwin setup code, it seems to
> "bootstrap" the Cygwin root directory, using only the Win32api, without
> a reliance of a Cygwin DLL at the early stage.

Install from local directory with an empty setup.ini.

s


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