[RFC] refactoring extra-special-file; an /etc/tmpfiles/ equivalent

[RFC] refactoring extra-special-file; an /etc/tmpfiles/ equivalent

[Attila Lendvai]

hello Guix,

context 1:

i want to write a string into a file at boot to disable wake-up by my keyboard (so that it doesn't immediately wake up my laptop after i suspend it). it requires doing this once per boot:

echo XHC >/proc/acpi/wakeup

the standard solution on systemd distros is to use a /etc/tmpfiles.d/disable-usb-wake.conf file, which systemd interprets (see e.g. https://forums.linuxmint.com/viewtopic.php?f=42&t=312953).


context 2:

i need to create an empty directory in an image created by `guix system vm ...` (for "reasons"; this is the simplest way i'm aware of to hack forward).


in Guix we have extra-special-file (what a strange name!) that in fact can do one thing: a (single shot?) shepherd service that can symlink something somewhere.

what i need is something like extra-special-file, but with a few more keyword arguments that would allow creating empty directories, and appending/overwriting files with content given as literals.

or something else that i'm not aware of?


solution 1:

i think i could backwards compatibly extend extra-special-file with the keyword args.

solution 2:

introduce a new abstraction (preferrably with a better name), and mark extra-special-file obsolete.

dear maintainers, any thoughts on which way i should start digging?

also, any suggestion for the API? the naming of the keyword args?

-- 
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
“Angry people want you to see how powerful they are… loving people want you to see how powerful You are.”
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Re: [RFC] refactoring extra-special-file; an /etc/tmpfiles/ equivalent

[Attila Lendvai]

> i want to write a string into a file at boot to disable wake-up by
> my keyboard (so that it doesn't immediately wake up my laptop after
> i suspend it). it requires doing this once per boot:
>
> echo XHC >/proc/acpi/wakeup
> 
> the standard solution on systemd distros is to use a
> /etc/tmpfiles.d/disable-usb-wake.conf file, which systemd interprets
> (see e.g. https://forums.linuxmint.com/viewtopic.php?f=42&t=312953).

FTR, the "guixy way" currently is to add a service like this:

(simple-service 'disable-keyboard-wakeup activation-service-type
  #~(begin
      (use-modules (ice-9 regex))
      (use-modules (ice-9 textual-ports))
      (when (string-match "XHC\t  S3\t\\*enabled"
                          (call-with-input-file "/proc/acpi/wakeup"
                            get-string-all))
        (display "Turning off usb wakeup\n")
        (with-output-to-file "/proc/acpi/wakeup"
          (lambda _
            (display "XHC"))))))

-- 
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
Censorship is telling a man he can't have a steak just because a baby can't chew it.

Re: [RFC] refactoring extra-special-file; an /etc/tmpfiles/ equivalent

[Attila Lendvai]

> FTR, the "guixy way" currently is to add a service like this:

as mirai kindly instructed me on IRC, even though it's a somewhat widely spread solution, this has issues, as documented in: https://issues.guix.gnu.org/60657

instead, the proper way is to add a full-fledged one-shot shepherd service:

(simple-service
  'disable-keyboard-wakeup
  shepherd-root-service-type
  (list
   (shepherd-service
    (requirement '(file-systems))
    (provision '(disable-keyboard-wakeup))
    (documentation "echo XHC >/proc/acpi/wakeup, so that my USB Kinesis keyboard doesn't wake up the laptop right after a suspend")
    (one-shot? #t)
    (start
     #~(begin
         (use-modules (ice-9 regex))
         (use-modules (ice-9 textual-ports))

         (lambda _
           (when (string-match "XHC\t  S3\t\\*enabled"
                               (call-with-input-file "/proc/acpi/wakeup"
                                 get-string-all))
             (display "Turning off usb wakeup\n")
             (with-output-to-file "/proc/acpi/wakeup"
               (lambda _
                 (display "XHC"))))))))))

and while we are at it, a newcomer feedback:

it's super confusing that there are 'guix services' and 'shepherd services', and they are rather different animals with very similar names, and they are present in a very confined context.

-- 
• attila lendvai
• PGP: 963F 5D5F 45C7 DFCD 0A39
--
“I will have to remember ‘I am here today to cross the swamp, not to fight all the alligators.’”
	— Rosamund and Benjamin Zander, 'The Art of Possibility' (2002)