# Extending from shepherd-root-service-type **URL:** \ **Category:** Guix\ **Created:** [June 12, 2026, 3:42am UTC](https://forum.systemcrafters.net/t/extending-from-shepherd-root-service-type/2053 "2026-06-12T03:42:21Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![aionfork](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.systemcrafters.net/aionfork/32/1243_2.png) [@aionfork](https://forum.systemcrafters.net/u/aionfork)\ **Post date:** [June 12, 2026, 3:42am UTC](https://forum.systemcrafters.net/t/extending-from-shepherd-root-service-type/2053/1 "2026-06-12T03:42:21Z")
I’m trying to consolidate some of the references in my source code. I have package names kinda everywhere, so i thought i’d bundle things using `service-type`. However, I’m running into some weird issues as I do I thought I could just pass service config values to `service-extension`. This is just a record. I figured out how to get past the `udev` issues, but for some reason, nothing I pass as a service extension to `shepherd-root-service-type` gets past `Wrong type to apply` ```scheme ;;; Copyright � 2025 David Conner (define-module (ellipsis services security-token) ;;#:use-module (ellipsis config) #:use-module (gnu home services) #:use-module (gnu) #:use-module (gnu packages) #:use-module (gnu packages gnupg) #:use-module (gnu packages libusb) #:use-module (gnu packages security-token) #:use-module (gnu services base) #:use-module (gnu services configuration) #:use-module (gnu services security-token) #:use-module (gnu services shepherd) #:use-module (gnu services) #:use-module (ellipsis packages golang-crypto) #:use-module (ellipsis packages security-token) #:use-module (ellipsis packages tls) #:use-module (guix gexp) #:use-module (guix records) #:use-module (srfi srfi-1) #:use-module (ice-9 pretty-print) #:export (yubikey-udev-rules)) ;;; Commentary: ;;; ;;; This module provides a service definition for system services related to ;;; security tokens. ;;; ;;; yubikey-udev-rules ;;; (define-public yubikey-udev-rules ;; needs plugdev, but warns if multiple instantiations create using #:groups (list (udev-rules-service 'fido2 libfido2 #:groups '("plugdev")) (udev-rules-service 'u2f libu2f-host) (udev-rules-service 'yubikey yubikey-personalization))) ;; hidapi: HID Devices for FIDO/OTP (define pkgs-smartcard (list opensc pinentry-tty hidapi libu2f-host libfido2)) (define pkgs-yubikey (list yubico-piv-tool yubikey-personalization python-yubikey-manager)) (define svc-pcscd (service pcscd-service-type)) (define-public ellipsis-smartcard-service-type (service-type (name 'ellipsis-smartcard) (extensions (list ;; pcsc-lite, ccid provided by service/activation (service-extension shepherd-root-service-type svc-pcscd) (service-extension udev-service-type (lambda (config) yubikey-udev-rules)) (service-extension profile-service-type (lambda (config) (append pkgs-yubikey pkgs-smartcard))))) (default-value '()) (description "Sets up some common services"))) ;;; security-token.scm ends here ``` Here’s the error: ```auto guix/ui.scm:1030:18: Wrong type to apply: #< type: # value: #< pcsc-lite: # usb-drivers: (#)>> ``` In [guix-hpc/guix-hpc-non-free ./hacky/services-gitlab.scm](https://gitlab.inria.fr/guix-hpc/guix-hpc-non-free/-/blob/9f297858106ce7f86b0a3849f9dd720a6863a0b4/hacky/services-gitlab.scm#L127-145), they use: ```scheme (define gitlab-runner-service-type (service-type (name 'gitlab-runner) (description "Run gitlab-runner daemon @command{gitlab-runner run}.") (extensions (list (service-extension account-service-type (const %gitlab-runner-accounts)) (service-extension shepherd-root-service-type (compose list gitlab-runner-shepherd-service)) (service-extension activation-service-type %gitlab-runner-activation) ;; 'gitlab-runner' wants to run Git, but since it runs its scripts ;; with 'bash --login', PATH is essentially limited to ;; /run/current-system/profile/bin. So put Git in there. (service-extension profile-service-type (const (list git-minimal))))) (default-value (gitlab-runner-configuration)))) ``` Where `gitlab-runner-shepherd-service` is a match-lambda, but otherwise returns the result of `(shepherd-service ...)`. What does `compose` do in `(compose list gitlab-runner-shepherd-service)`, specifically? In other codebases, I often see `(lambda (config) ...)` passed in. It’s a block that returns something that the service-type definition would know how to compose/apply. Why does that not work here? ---
**Author:** ![hako](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.systemcrafters.net/hako/32/1192_2.png) [@hako](https://forum.systemcrafters.net/u/hako)\ **Post date:** [June 12, 2026, 8:49am UTC](https://forum.systemcrafters.net/t/extending-from-shepherd-root-service-type/2053/2 "2026-06-12T08:49:51Z")
Guix services are different from Shepherd services. `shepherd-root-service-type` is a type of Guix service, which extends Guix System with the ability to manage daemons. Take a look at `guix system edit shepherd-root`: ```scheme (define shepherd-root-service-type (service-type ... (compose concatenate) (extend (lambda (config extra-services) (shepherd-configuration (inherit config) (services (append (shepherd-configuration-services config) extra-services))))) (default-value (shepherd-configuration)))) ``` The service type accepts a configuration value of `shepherd-configuration`, and can be extended with a list of `shepherd-service` (this is what the `services` field of the `` record expects). ```scheme (define-record-type* ... (services shepherd-configuration-services (default '()))) ; list of ``` And the `(service pcscd-service-type)` you used creates a service instance, which is different from both a service type and the shepherd-service we want. Then take a look at `guix system edit pcscd`: ```scheme (define pcscd-service-type (service-type ... (extensions (list (service-extension shepherd-root-service-type (compose list pcscd-shepherd-service)) ...)) ``` The service type extends `shepherd-root-service-type` with a list of `shepherd-service` created by the `pcscd-shepherd-service` procedure. (The `pcscd-shepherd-service` procedure is not publicly exported so you can’t refer to it normally, and is not very useful for your use case, since it’s closely tied to the implementation of `pcscd-service-type`) BTW the `udev-rules-service` defines service types which are not expected for extending `udev-service-type`. The service type should be extended by a list of file-like objects, like packages. * * * To address your issue, you can either extend `shepherd-root-service-type` with a list of `shepherd-service`, then extend `udev-service-type` and `account-service-type` (that’s how the `#:groups` keyword is implemented) like what `udev-rules-service` does. I recommend learning it if you have time, the service part of Guix is quite interesting. or instantiate service instance without explicitly defining a service type via `simple-service`: ```scheme (service pcscd-service-type) (udev-rules-service 'fido2 libfido2 #:groups '("plugdev")) (udev-rules-service 'u2f libu2f-host) (udev-rules-service 'yubikey yubikey-personalization) (simple-service 'ellipsis-smartcard-profile-service profile-service-type (append pkgs-yubikey pkgs-smartcard)) ``` In this approach you can also organize these service instances as a list and append it into your operating system declaration. ---
**Author:** ![aionfork](https://yyz1.discourse-cdn.com/flex029/user_avatar/forum.systemcrafters.net/aionfork/32/1243_2.png) [@aionfork](https://forum.systemcrafters.net/u/aionfork)\ **Post date:** [June 12, 2026, 9:15am UTC](https://forum.systemcrafters.net/t/extending-from-shepherd-root-service-type/2053/3 "2026-06-12T09:15:46Z")
thanks, i appreciate the writeup. i think a list of services is about as simple as i can get it.