Re: how to create and test a new service definition

[Vincent Legoll <vincent.legoll@gmail.com>]

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.
Backtrace:
In ice-9/boot-9.scm:
 160: 10 [catch #t #<catch-closure 8c5b80> ...]
In unknown file:
   ?: 9 [apply-smob/1 #<catch-closure 8c5b80>]
In ice-9/boot-9.scm:
  66: 8 [call-with-prompt prompt0 ...]
In ice-9/eval.scm:
 432: 7 [eval # #]
In ice-9/boot-9.scm:
2412: 6 [save-module-excursion #<procedure 8e67c0 at
ice-9/boot-9.scm:4084:3 ()>]
4089: 5 [#<procedure 8e67c0 at ice-9/boot-9.scm:4084:3 ()>]
1734: 4 [%start-stack load-stack #<procedure 8f69c0 at
ice-9/boot-9.scm:4080:10 ()>]
1739: 3 [#<procedure 8f86c0 ()>]
In unknown file:
   ?: 2 [primitive-load
"/gnu/store/rdpki7xkanivgb7jdczvk27kma47rj54-qemu-image-builder"]
In ./gnu/build/vm.scm:
 126: 1 [load-in-linux-vm
"/gnu/store/6mcs53r3ggy3csq7z4hwhx2iccfds3yn-linux-vm-loader" ...]
In unknown file:
   ?: 0 [scm-error misc-error #f "~A ~S" ("qemu failed"
"qemu-system-x86_64") #f]

ERROR: In procedure scm-error:
ERROR: qemu failed "qemu-system-x86_64"
environment variable `PATH' set to
`/gnu/store/rh3953267ifpb5bpl3l0f9vcmkx6zgl5-qemu-minimal-2.9.0/bin:/gnu/store/6908gy3pws0ccys49ni98idwnicchlr2-coreutils-8.26/bin'
builder for `/gnu/store/g2zyq34flqswxaikr0m774aizwbh0xdm-qemu-image.drv'
failed with exit code 1
cannot build derivation
`/gnu/store/qh5rvmv7rss59w4prb4bwq0r1m0jqwql-run-vm.sh.drv': 1
dependencies couldn't be built
guix system: error: build failed: build of
`/gnu/store/qh5rvmv7rss59w4prb4bwq0r1m0jqwql-run-vm.sh.drv' failed

Looks like kvm is there though, in my qemu guixsd VM:

vince@guixsd ~$ l /dev/*kvm*
crw-rw---- 1 root kvm 10, 232 May 14 10:36 /dev/kvm

Maybe use of qemu without hw assisted kvm would work when already in a
virtualized environment...

> ‘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:

> <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 ?

> 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 ?

>> 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 ?

-- 
Vincent Legoll