Re: guix package: error: build failed: opening lock file?

[Chris Marusich <cmmarusich@gmail.com>]

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Hi,

This is follow-up to a help-guix@gnu.org thread in which George asked if
it is expected that "guix system vm" mounts the store read-only in the
VM, and I replied explaining that it is expected:

https://lists.gnu.org/archive/html/help-guix/2018-04/msg00049.html

I dug a little further and discovered behavior that seems undesirable to
me.  If someone can confirm my understanding, I would be happy to try
drafting draft a patch to fix the problem.

Chris Marusich <cmmarusich@gmail.com> writes:

> Currently, if you need a read-write store in a VM, the easiest solution
> is probably to use "guix system vm-image" or "guix system disk-image".

Curiously, if you invoke "guix system vm --full-boot", you will get a VM
that sees a read-write store.  In virtualized-operating-system, it says:

    ;; XXX: When FULL-BOOT? is true, do not add a 9p mount for /gnu/store
    ;; since that would lead the bootloader config to look for the kernel and
    ;; initrd in it.
    (file-systems (if full-boot?
                      virtual-file-systems
                      (cons
                       (file-system
                         (inherit (mapping->file-system %store-mapping))
                         (needed-for-boot? #t))
                       virtual-file-systems)))))

I don't understand this comment.  I don't understand why we only map the
store into the VM when full-boot? is #f.  When --full-boot is specified
on the command line (i.e., full-boot? is not #f), not only do we NOT map
the store into the VM, but we also copy the VM's dependencies into the
VM's disk image, so the disk image will contain a subset of the host's
store.  In fact, because we copy the files over, the size of the disk
image produced by "guix system vm --full-boot" is about the same as that
produced by "guix system vm-image".  I don't understand the point of
this; it seems to me like we could always unconditionally map the store
into the VM (without copying the dependencies required by the bootloader
config), regardless of whether --full-boot was specified, and the
bootloader would still successfully find its kernel and initrd.

Am I wrong?  Does anyone understand why we map the store into the VM if
and only if full-boot? is #f?

-- 
Chris

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