System-level inferiors.

[brettg]

Hey all,

I am experimenting with the inferior system a little bit. I am 
attempting to see if I can specify a specific version of the linux-libre 
kernel to be taken from an inferior and applied to my system 
configuration.

(define kernel-channel-inf
  ;; This is the old revision from which
  ;; we will obtain our desired kernel version.
  (list (channel
         (name 'guix)
         (url "https://git.savannah.gnu.org/git/guix.git";)
         (commit
          "fd41243c819635795f4e4bdef1e2823db5234e24"))))

(define kernel-inferior-proc
  ;; An inferior representing `kernel-channel-inf'.
  (inferior-for-channels kernel-channel-inf))

(operating-system

  ...

 (kernel (lookup-inferior-packages
          kernel-inferior-proc "linux-libre" "4.19.81"))

It took me some experimenting to come up with this, in that 
experimenting the channel revision was built and cached. However, when I 
run `guix system build config.scm` with the above code snippet, the 
process just hangs on

Updating channel 'guix' from Git repository at 
'https://git.savannah.gnu.org/git/guix.git'...

I am not sure how to proceed to achieve what I am hoping for. Any 
thoughts?

Brett Gilio