Re: how to create and test a new service definition

[ludo@gnu.org (Ludovic Courtès)]

Hi,

Vincent Legoll <vincent.legoll@gmail.com> skribis:

> On Sat, May 13, 2017 at 10:06 PM, Ludovic Courtès <ludo@gnu.org> wrote:
>> Vincent Legoll <vincent.legoll@gmail.com> skribis:
>>> ERROR: qemu failed "qemu-system-x86_64"
>>
>> What were the lines above this one?  This tool tries to use KVM if it
>> seems available.  Maybe in your case it “seems” to be available (as in
>> /dev/kvm exists) but is actually unusable?
>
> Formatting '/gnu/store/miyri69r76ji72y6aq5xci8z2j68n5s1-qemu-image',
> fmt=qcow2 size=31457280 encryption=off cluster_size=65536
> lazy_refcounts=off refcount_bits=16
> qemu-system-x86_64: error: failed to set MSR 0xd90 to 0x0
> qemu-system-x86_64:
> /tmp/guix-build-qemu-minimal-2.9.0.drv-0/qemu-2.9.0/target/i386/kvm.c:1833:
> kvm_put_msrs: Assertion `ret == cpu->kvm_msr_buf->nmsrs' failed.

A quick search gave me this:
<https://bugs.launchpad.net/qemu/+bug/1661386>.  It mentions a potential
VMware bug; are you using VMware for the “outer” VM?

>> ‘GUIX_PACKAGE_PATH’ is documented at
>> <https://www.gnu.org/software/guix/manual/html_node/Package-Modules.html#index-GUIX_005fPACKAGE_005fPATH>.
>
> Yes, that's where I finally found it again, with google's help, I
> first searched there:

I would recommend using the index in Info or one of:

  https://www.gnu.org/software/guix/manual/html_node/Concept-Index.html
  https://www.gnu.org/software/guix/manual/html_node/Programming-Index.html

>> <https://www.gnu.org/software/guix/manual/html_node/Defining-Packages.html>,
>> <https://www.gnu.org/software/guix/manual/html_node/Submitting-Patches.html>.
>
> So I think adding something to these pages, maybe only linking to where it is
> described would have been sufficient... WDYT ?

OK, I’ve added a cross-ref from “Defining Packages” to “Package Modules”.

>> There’s probably room for improvement though.  What changes/additions
>> would you suggest?
>
> I would suggest having a paragraph or 2 about how to setup a dev environment:
> - using GUIX_PACKAGE_PATH
> - setting up a link (where ?) to a local guix checkout
>
> I read "8.1 Building from Git" and was frustrated by its avoidance to explain
> how to do it. This is the logical (at least for me) place where this should be
> explained.
>
> I can try to add something about the env var, but cannot do the link thing, I
> think this is what Catonano is speaking about :
>
>> George suggested me the trick to link a checked out master branch to
>> .local/guix/profile (or maybe it's the other way around: it's linking
>> .local/guix/profile to a checked out master branch)
>
> WDYT ?

I’m not sure what you’re suggesting.  Could you post a draft patch?  We
can work from there.

>>> guix edit is throwing me :
>>> E166: Can't open linked file for writing
>>
>> This error does not come from ‘guix edit’, but maybe from your editor.
>> As for why the file is read-only, see
>> <https://www.gnu.org/software/guix/manual/html_node/Invoking-guix-edit.html>.
>
> And here is the other place where that variable is talked about, I
> really fumbled
> my research... So if something more substantial is put in 8.1, maybe we can just
> link to it from there too...
>
> Another idea, would be to enhance guix edit, like that:
> if there's a user writable place for package definitions (either
> GUIX_PACKAGE_PATH or a link to a local git checkout, or...), then guix edit
> make a temp copy of the store file, if it is not modified, the copy is
> thrown away
> at guix edit exit and if it is modified, kept there...
>
> WDYT ?

This is a great idea that’s been discussed before, and I would really
like to see it.  That said, it’s a “wishlist” item more than something
directly actionable.  Could you send this suggestion to bug-guix so we
can keep track of it?

Thanks,
Ludo’.