Re: How to handle package udev rules?

[gyps]

Dear Danny, dear Tobias,

thanks for the hints which immediately solved my issue.
It now compiles and everyting is fine but one thing.

If I change my operating-system config to inlcude udev-rules from
package "projecteur" everything works fine - at least if I do it as a
regular user. As soon as I sudo the guix system reconfigure command the
package is known but it's code is not. Error message is:

> $ sudo guix system reconfigure ~/etc/config.scm
> ice-9/boot-9.scm:3329:6: In procedure resolve-interface:
> no code for module (projecteur)

Could it be the case that sudo'ed the variable GUIX_PACKAGE_PATH is not
known or not interpreted correctly? Does the package need to reside
somewhere else than in GUIX_PACKAGE_PATH?

Cheers,

Alex

On Sun, Dec 12 2021, 19:17:26, Danny Milosavljevic <dannym@scratchpost.org> 
wrote:

> [[PGP Signed Part:Undecided]]
> Hello Alexander,
>
> On Sun, 12 Dec 2021 13:12:50 +0100
> Alexander Asteroth <alexander.asteroth@h-brs.de> wrote:
>
>> I tried to import the libgudev module but that that only results in the
>> package wanting to write to another write-protected directory from the
>> store.
>
> It's supposed to write those to $output/lib/udev/rules.d (s.t. there's
> *.rules inside) instead.   There's usually a cmake variable to make it do
> that--but you need to look at the CMakeLists.txt in question.
>
> Guix will pick those up if they originate in something it can see and add
> those to Guix's udev service automatically (via the service extension 
> mechanism,
> which allows you to extend service config from outside the udev service).
>
> Are you using Guix as an operating system? Or on top of another distribution?
>
>> As I understand, the udev-rules are usually created on system level.
>
> Yes.
>
>> That would mean I need to split the package into a service part
>> and a package part? And remove the installation of the udev-file from
>> the package install process?
>
> Kinda not really--at least not exactly.  See below.
>
> Example I'm using (that one definitely works--but I only add the custom
> package because the upstream package doesn't do it![1]):
>
> /etc/config.scm :
>
> (define my-ledger-nano
>   (package
>     (name "my-ledger-nano")
>     (version "1")
>     (source #f)
>     (build-system trivial-build-system)
>     (synopsis "")
>     (description "")
>     (license #f)
>     (home-page #f)
>     (arguments
>      `(#:builder
>        (begin
>          (mkdir %output)
>          (mkdir (string-append %output "/lib"))
>          (mkdir (string-append %output "/lib/udev"))
>          (mkdir (string-append %output "/lib/udev/rules.d"))
>          (call-with-output-file (string-append %output 
> "/lib/udev/rules.d/99-my-ledger-nano.rules")
>            (lambda (port)
>              (format port
> "SUBSYSTEM==\"usb\", ATTRS{idVendor}==\"2c97\", MODE=\"0600\", 
> OWNER=\"dannym\", TAG+=\"uaccess\", TAG+=\"udev-acl\"
> KERNEL==\"hidraw*\", ATTRS{idVendor}==\"2c97\", MODE=\"0600\", 
> OWNER=\"dannym\", SYMLINK+=\"ledger_%n\", TAG+=\"uaccess\", TAG+=\"udev-acl\"
> ")))
>          #t)))))
>
> (operating-system
>   ...
>   (services
>             (simple-service 'custom-udev-rules udev-service-type (list 
> sane-backends my-ledger-nano)))
>
> You can add your package reference there and it will work.
>
> Or you can try adding your package reference into
>   (operating-system (packages (list ...)))--should be enough.
>
> If you mean adding your package's udev rules to the operating system
> configuration without being the "root" user in-between: no, that would be a
> (very bad! those rules run as root!) security problem.
>
> In the case of your package, it seems[0] that they calculate the directory to
> store the udev rules to from pkg-config--which will result in the udev
> package's install directory. That won't work.
>
> But in line 214 in [0] they seem to allow you to override it anyway.
> So you can try to call cmake with
>
>   -DCMAKE_INSTALL_UDEVRULESDIR=$output//lib/udev/rules.d
>
> like this (in your package definition):
>
> (package
>   ...
>   (arguments
>  '(#:configure-flags (list (string-append "-DCMAKE_INSTALL_UDEVRULESDIR="
>                                           (assoc-ref %outputs "out")
>                                           "/lib/udev/rules.d"))))
>
> [0] https://github.com/jahnf/Projecteur/blob/develop/CMakeLists.txt#L231
> [1] https://github.com/LedgerHQ/udev-rules/pull/8
>
> [[End of PGP Signed Part]]