Install image with custom services

Install image with custom services

[Jack Hill]

Hello Guix,

I'm trying to create an installation image that uses Network Manager to 
configure networking (For use at a site with WPA-Enterprise networks). I 
came up with the following:

```scheme
(define-module (jackhill system install)
   #:use-module ((gnu packages gnome) #:select (network-manager) #:prefix package:)
   #:use-module (gnu services)
   #:use-module (gnu services networking)
   #:use-module (gnu system)
   #:use-module (gnu system install)
   #:use-module (srfi srfi-1)
   #:export (my-installation-os))

(define my-installation-os
   (operating-system
     (inherit installation-os)
     (packages (cons package:network-manager
 		     (operating-system-packages installation-os)))
     (services (cons (service network-manager-service-type)
                 (remove (lambda (service)
     		          (eq? (service-kind service) connman-service-type))
     		        (operating-system-services installation-os))))))

my-installation-os
```

However, passing that to guix system disk-image results in:

```
guix system: error: more than one target service of type 'shepherd-root'
```

Thinking that I had done something wrong with removing the connman-service 
and adding the network-manager-service, I created a more minimal operating 
system definition:

```scheme
(define my-installation-os
   (operating-system
     (inherit installation-os)
     (packages (cons package:network-manager
 		     (operating-system-packages installation-os)))
     (services (operating-system-services installation-os))))
```

To my surprise, this also fails with

```
guix system: error: more than one target service of type 'account'
```

However,

```scheme
(define my-installation-os
   (operating-system
     (inherit installation-os)
     (packages (cons package:network-manager
 		     (operating-system-packages installation-os)))))
```

sucseeds.

Should these last two operating system definitions not be equivalent? 
What's going on here?

Thanks,
Jack

Re: Install image with custom services

[Jack Hill]

On Thu, 19 Dec 2019, Jack Hill wrote:

> I created a more minimal operating system definition:
>
> ```scheme
> (define my-installation-os
>  (operating-system
>    (inherit installation-os)
>    (packages (cons package:network-manager
> 		     (operating-system-packages installation-os)))
>    (services (operating-system-services installation-os))))
> ```
>
> To my surprise, this also fails with
>
> ```
> guix system: error: more than one target service of type 'account'
> ```

However, replacing

(operating-system-services installation-os)

with

(@@ (gnu system install) %installation-services)

works.

What am I not understanding about how the former works?

Best,
Jack