Noob issues with maintaining a guix laptop system

[Divan Santana]

Hi All,

Issues of a noob with no lisp programming skills has in maintaining a
guix laptop system.

 * how to do a system reconfigure on an older guix generation?

Sometimes I do a guix pull and attempt a reconfigure. Due to various
reasons, the reconfigure may fail. I now want to do a reconfigure, but
on the older guix generation profile. How do I go about doing that?

I've tried rolling back my guix profile, but running =guix pull
--list-generations= fails.

  #+begin_example
    ~ ᐅ guix pull --list-generations
    Generation 1    Oct 12 2018 20:44:32
      guix aa227b3
        repository URL: https://git.savannah.gnu.org/git/guix.git
        branch: master
        commit: aa227b3be3d7728331a08dbd139c47c9b271dc23
      guix-chromium 16130df
        repository URL: https://gitlab.com/mbakke/guix-chromium.git
        branch: master
        commit: 16130df2cc9a3424caa8230323b7d49c445f0813
    Generation 2    Oct 13 2018 15:35:07
      guix d781469
        repository URL: https://git.savannah.gnu.org/git/guix.git
        branch: master
        commit: d7814696b884a7c5e4a58f539ece53f4998689a3
      guix-chromium 16130df
        repository URL: https://gitlab.com/mbakke/guix-chromium.git
        branch: master
        commit: 16130df2cc9a3424caa8230323b7d49c445f0813
    Backtrace:
              10 (primitive-load "/home/ds/.config/guix/current/bin/guix")
    In guix/ui.scm:
      1747:12  9 (run-guix-command _ . _)
    In ice-9/boot-9.scm:
        829:9  8 (catch _ _ #<procedure 7f2580061910 at guix/ui.scm:703…> …)
        829:9  7 (catch _ _ #<procedure 7f2580061928 at guix/ui.scm:826…> …)
        829:9  6 (catch _ _ #<procedure 7f257daedba0 at guix/scripts/pu…> …)
        829:9  5 (catch system-error #<procedure 41c66a0 at guix/script…> …)
    In guix/scripts/pull.scm:
       479:15  4 (_)
        462:4  3 (display-profile-content-diff "/var/guix/profiles/per-…" …)
    In guix/memoization.scm:
        100:0  2 (_ #<hash-table 414aa60 0/31> "/var/guix/profiles/per-…" …)
    In guix/scripts/pull.scm:
       363:21  1 (_)
    In guix/inferior.scm:
        151:7  0 (port->inferior _ _)

    guix/inferior.scm:151:7: In procedure port->inferior:
    no binding `console-setup' in module (gnu packages xorg)
  #+end_example

Any ideas?

 * Adding a swap device from a file on disk

Something like this:

~ sudo file /mnt/swapfile
Password:
/mnt/swapfile: Linux/i386 swap file (new style) with SWSUSP1 image

(operating-system
   ...
   (swap-devices '("/mnt/swapfile"))
   ...
   )

But fails with:

#+begin_example
  guix system: error: exception caught while executing 'start' on service 
'swap-/mnt/swapfile':
  In procedure swapon: "/mnt/swapfile": Invalid argument
#+end_example