bug#73859: lightdm-service-type is almost unusable

bug#73859: lightdm-service-type is almost unusable

[Dariqq]

Hi Guix,

This is to report some of the issues and workarounds when trying to 
setup lightdm-service-type.


1. Unable to choose a session (https://issues.guix.gnu.org/68055)

This appearently never worked: https://issues.guix.gnu.org/57168#0

This means one currently has to specify the default session with 
something like

(service lightdm-service-type
	 (lightdm-configuration
	  (seats
	   (list
	    (lightdm-seat-configuration
	     (name "*")
	     (user-session "xfce"))))))

2. gtkgreeter chooses the wrong default session

This is related to 1. If one already had set the default user session 
(i.e. from using default configuration => default.xsession) or one wants 
to use a different session, lightdm gtkgreeter still requests the old one.

After a lot of searching I found this 
https://github.com/Xubuntu/lightdm-gtk-greeter/issues/163 .

I.e. lightdm asks the accountsservice for the default-session rather 
than lightm which still has cashed the old/wrong one. Thus with no 
option to select a different session one is unable to login.

The workaorund here is to delete/modify /var/lib/AccountService/users to 
make sure accountsservice recreates/updates the configurration.


3. After the lightdms users .Xauthority file is created it has wrong 
permissions on subsequent boots.

this can be "fixed" by manually setting less restrictive permissions on 
/var/lib/lightdm/.Xauthority

This might be fixed by making the lightdm-activiation snippet actually 
useful: It currently searches for a file named "directory" to fix 
permissions rather than the content of the variable 'directory'.

(find-files "directory"  #:directories? #t) vs
(find-files directory  #:directories? #t)

here 
https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/services/lightdm.scm#n527

4. tigervnnc

default tigervnc is (file-append tigervnc-server "bin/Xvnc") rather than 
(file-append tigervnc-server "/bin/Xvnc")

bug#73859: lightdm-service-type is almost unusable

[Maxim Cournoyer]

Hi Dariqq,

Dariqq <dariqq@posteo.net> writes:

> Hi Guix,
>
> This is to report some of the issues and workarounds when trying to
> setup lightdm-service-type.

Thank you for taking the time to report these detailed findings!

>
> 1. Unable to choose a session (https://issues.guix.gnu.org/68055)
>
> This appearently never worked: https://issues.guix.gnu.org/57168#0

Indeed.  This definitely makes the session manager much less useful.
I'd really like to find a solution to that; I think the issue is
reported upstream here:
https://github.com/Xubuntu/lightdm-gtk-greeter/issues/105.

Just a hunch: perhaps something in the  environment the greeter
runs is missing to have d-bus communication properly working?

> This means one currently has to specify the default session with
> something like
>
> (service lightdm-service-type
> 	 (lightdm-configuration
> 	  (seats
> 	   (list
> 	    (lightdm-seat-configuration
> 	     (name "*")
> 	     (user-session "xfce"))))))
>

[...]

> This might be fixed by making the lightdm-activiation snippet actually
> useful: It currently searches for a file named "directory" to fix
> permissions rather than the content of the variable 'directory'.
>
> (find-files "directory"  #:directories? #t) vs
> (find-files directory  #:directories? #t)
>
> here
> https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/services/lightdm.scm#n527

Fixed.

> 4. tigervnnc
>
> default tigervnc is (file-append tigervnc-server "bin/Xvnc") rather
> than (file-append tigervnc-server "/bin/Xvnc")

Also fixed (see commit e4e1e16bc1).

-- 
Thanks,
Maxim

bug#73859: lightdm-service-type is almost unusable

[Dariqq]

[-- Attachment #1: Type: text/plain, Size: 2967 bytes --]

Hi Maxim

On 23.10.24 16:48, Maxim Cournoyer wrote:
> Hi Dariqq,
> 
> Dariqq <dariqq@posteo.net> writes:
> 
>> Hi Guix,
>>
>> This is to report some of the issues and workarounds when trying to
>> setup lightdm-service-type.
> 
> Thank you for taking the time to report these detailed findings!
> 
>>
>> 1. Unable to choose a session (https://issues.guix.gnu.org/68055)
>>
>> This appearently never worked: https://issues.guix.gnu.org/57168#0
> 
> Indeed.  This definitely makes the session manager much less useful.
> I'd really like to find a solution to that; I think the issue is
> reported upstream here:
> https://github.com/Xubuntu/lightdm-gtk-greeter/issues/105.
> 
> Just a hunch: perhaps something in the  environment the greeter
> runs is missing to have d-bus communication properly working?
> 
Found all these while trying to switch from xfce to mate on a 32 bit 
machine (plus skipping some tests in mates dependency tree to get it to 
build) and spent way to much time trying to understand how to change the 
default session.

Remotivated by your response I looked into how the greeter actually 
finds the session:

1. The menu just calls out to lightdm_get_sessions
https://github.com/Xubuntu/lightdm-gtk-greeter/blob/master/src/lightdm-gtk-greeter.c#L3186

2. This eventually reaches update_sessions
https://github.com/canonical/lightdm/blob/main/liblightdm-gobject/session.c#L181

Could it just be that it is using the "wrong" values for the session dir 
and not the ones we specified in the lightdm config?
 From what config files (if any) are we reading here?


If this is indeed the issue can we set sysconfdir to /etc and let it 
read the lightdm config file from /etc/lightdm/lightdm.conf (via 
config_load_from_standard_locations)?

I tried something like this (diff attached) and seems to work. I was 
able to choose between xfce and mate and log into either of them.
(only slightly awkward thing is that wed need to overwrite sysconfdir 
for 'make install' and should probably rename the 
lightdm-configuration->greeters-config-dir function).



>> This means one currently has to specify the default session with
>> something like
>>
>> (service lightdm-service-type
>> 	 (lightdm-configuration
>> 	  (seats
>> 	   (list
>> 	    (lightdm-seat-configuration
>> 	     (name "*")
>> 	     (user-session "xfce"))))))
>>
> 
> [...]
> 
>> This might be fixed by making the lightdm-activiation snippet actually
>> useful: It currently searches for a file named "directory" to fix
>> permissions rather than the content of the variable 'directory'.
>>
>> (find-files "directory"  #:directories? #t) vs
>> (find-files directory  #:directories? #t)
>>
>> here
>> https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/services/lightdm.scm#n527
> 
> Fixed.
> 
>> 4. tigervnnc
>>
>> default tigervnc is (file-append tigervnc-server "bin/Xvnc") rather
>> than (file-append tigervnc-server "/bin/Xvnc")
> 
> Also fixed (see commit e4e1e16bc1).
> 

Thanks :)

[-- Attachment #2: lightdm.diff --]
[-- Type: text/x-patch, Size: 2286 bytes --]

diff --git a/gnu/packages/display-managers.scm b/gnu/packages/display-managers.scm
index 5152eb6479..b210b11bc6 100644
--- a/gnu/packages/display-managers.scm
+++ b/gnu/packages/display-managers.scm
@@ -385,6 +385,7 @@ (define-public lightdm
       #:parallel-tests? #f             ; fails when run in parallel
       #:configure-flags
       #~(list "--localstatedir=/var"
+              "--sysconfdir=/etc"
               "--enable-gtk-doc"
               ;; Otherwise the test suite fails on such a warning.
               "CFLAGS=-Wno-error=missing-prototypes")
@@ -412,7 +413,11 @@ (define-public lightdm
                 `("GI_TYPELIB_PATH" ":" prefix (,(getenv "GI_TYPELIB_PATH"))))
               ;; Avoid printing locale warnings, which trip up the text
               ;; matching tests.
-              (unsetenv "LC_ALL"))))))
+              (unsetenv "LC_ALL")))
+          (replace 'install
+           (lambda* (#:key make-flags #:allow-other-keys)
+             (apply invoke "make" "install" (string-append "sysconfdir=" #$output "/etc")
+                    make-flags))))))
     (inputs
      (list audit
            bash-minimal                 ;for cross-compilation
diff --git a/gnu/services/lightdm.scm b/gnu/services/lightdm.scm
index 798c106563..9dff263854 100644
--- a/gnu/services/lightdm.scm
+++ b/gnu/services/lightdm.scm
@@ -401,10 +401,11 @@ (define (lightdm-configuration->greeters-config-dir config)
   "Return a directory containing all the serialized greeter configurations
 from CONFIG, a <lightdm-configuration> object."
   (file-union "etc-lightdm"
-              (append-map (lambda (g)
-                            `((,(greeter-configuration->conf-name g)
-                               ,(greeter-configuration->file g))))
-                          (lightdm-configuration-greeters config))))
+              (cons `("lightdm.conf" ,(lightdm-configuration-file config))
+               (append-map (lambda (g)
+                             `((,(greeter-configuration->conf-name g)
+                                ,(greeter-configuration->file g))))
+                           (lightdm-configuration-greeters config)))))
 
 (define (lightdm-configuration->packages config)
   "Return all the greeter packages and their assets defined in CONFIG, a

bug#73859: lightdm

[Feng Shu]

Wow, good news.

Some month ago, I have spend many times to find why session can not be
found, but not success


-- 

bug#73859: lightdm

[Feng Shu]

I have tested and found that:


In lightdm-gtk-greeter, the following line run success and return no session.

   items = lightdm_get_sessions ();


But, in lightdm, the following function in liblightdm-gobject/session.c is not called:

/**
 * lightdm_get_sessions:
 *
 * Get the available sessions.
 *
 * Return value: (element-type LightDMSession) (transfer none): A list of #LightDMSession
 **/
GList *
lightdm_get_sessions (void)
{
    g_debug ("Run lightdm_get_sessions");
    update_sessions ();
    return local_sessions;
}


I do not know why, seem to very confuse.


-- 

bug#73859: [PATCH 0/2] lightdm: Fix empty session list.

[Dariqq]

This changes lightdm and the service to use the config file from a well-known location in /etc/lightdm/lightdm.conf s.t. the gtk-greeter knows about our custom "sessions-directory".

I then removed the custom config file from the lightdm servcice and removed passing XDG_CONFIG_DIRS which are no longer neccesary.

Renamed lightdm-configuration->greeters-config-dir to just lightdm-configuration-directory (inspired by how the dbus-service names its directory) and also moved the etc-extension into a seperate procedure for consistency with other services.


I tested this on my i686 pc and ran 'make check-system TESTS=lightdm' successfully


This is also the approach done on NixOS, see

* https://github.com/NixOS/nixpkgs/blob/nixos-unstable/pkgs/applications/display-managers/lightdm/default.nix#L93
*https://github.com/NixOS/nixpkgs/blob/nixos-unstable/nixos/modules/services/x11/display-managers/lightdm.nix#L259

Fixes https://issues.guix.gnu.org/68055


Dariqq (2):
  gnu: lightdm: Use global sysconfdir.
  gnu: lightdm-service-type: Add lightdm.conf to /etc/lightdm.

 gnu/packages/display-managers.scm |  7 ++++-
 gnu/services/lightdm.scm          | 48 ++++++++++++++-----------------
 2 files changed, 27 insertions(+), 28 deletions(-)


base-commit: ea11d3608566174c4bae70faa4f9d0c67748d2db
-- 
2.46.0

bug#73859: [PATCH 1/2] gnu: lightdm: Use global sysconfdir.

[Dariqq]

* gnu/packages/display-managers.scm (lightm)
[#:configure-flags]: Set sysconfdir to /etc.
[#:phases]: Overwrite sysconfdir in 'installE. for installing sample config files

Change-Id: If9c6ce810c726551bd3bf568d50cad8680829262
---
 gnu/packages/display-managers.scm | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/gnu/packages/display-managers.scm b/gnu/packages/display-managers.scm
index 5152eb6479..b210b11bc6 100644
--- a/gnu/packages/display-managers.scm
+++ b/gnu/packages/display-managers.scm
@@ -385,6 +385,7 @@ (define-public lightdm
       #:parallel-tests? #f             ; fails when run in parallel
       #:configure-flags
       #~(list "--localstatedir=/var"
+              "--sysconfdir=/etc"
               "--enable-gtk-doc"
               ;; Otherwise the test suite fails on such a warning.
               "CFLAGS=-Wno-error=missing-prototypes")
@@ -412,7 +413,11 @@ (define-public lightdm
                 `("GI_TYPELIB_PATH" ":" prefix (,(getenv "GI_TYPELIB_PATH"))))
               ;; Avoid printing locale warnings, which trip up the text
               ;; matching tests.
-              (unsetenv "LC_ALL"))))))
+              (unsetenv "LC_ALL")))
+          (replace 'install
+           (lambda* (#:key make-flags #:allow-other-keys)
+             (apply invoke "make" "install" (string-append "sysconfdir=" #$output "/etc")
+                    make-flags))))))
     (inputs
      (list audit
            bash-minimal                 ;for cross-compilation
-- 
2.46.0

bug#73859: [PATCH 2/2] gnu: lightdm-service-type: Add lightdm.conf to /etc/lightdm.

[Dariqq]

* gnu/services/lightdm.scm
(lightdm-configuration->greeters-config-dir): Rename to
lightdm-configuration-directory and add the lightdm-configuration-file.
(lightdm-shepherd-service): Don't pass the configuration file, don't set
XDG_CONFIG_DIRS
(lightdm-etc-service): New procedure.
(lightdm-service-type): Use lightdm-etc-service as the etc-extension.

Change-Id: I982ec1f7bdfd085621f45a8a1e4b175ab481202f
---
 gnu/services/lightdm.scm | 48 ++++++++++++++++++----------------------
 1 file changed, 21 insertions(+), 27 deletions(-)

diff --git a/gnu/services/lightdm.scm b/gnu/services/lightdm.scm
index 798c106563..191cb5635b 100644
--- a/gnu/services/lightdm.scm
+++ b/gnu/services/lightdm.scm
@@ -397,15 +397,6 @@ (define-configuration/no-serialization lightdm-configuration
    (list-of-strings '())
    "Extra configuration values to append to the LightDM configuration file."))
 
-(define (lightdm-configuration->greeters-config-dir config)
-  "Return a directory containing all the serialized greeter configurations
-from CONFIG, a <lightdm-configuration> object."
-  (file-union "etc-lightdm"
-              (append-map (lambda (g)
-                            `((,(greeter-configuration->conf-name g)
-                               ,(greeter-configuration->file g))))
-                          (lightdm-configuration-greeters config))))
-
 (define (lightdm-configuration->packages config)
   "Return all the greeter packages and their assets defined in CONFIG, a
 <lightdm-configuration> object, as well as the lightdm package itself."
@@ -496,6 +487,16 @@ (define (lightdm-configuration-file config)
                                        lightdm-seat-configuration-fields)))
           seats))))
 
+(define (lightdm-configuration-directory config)
+  "Return a directory containing the serialized lightdm configuration
+and all the serialized greeter configurations from CONFIG."
+  (file-union "etc-lightdm"
+              (cons `("lightdm.conf" ,(lightdm-configuration-file config))
+                    (map (lambda (g)
+                           `(,(greeter-configuration->conf-name g)
+                             ,(greeter-configuration->file g)))
+                         (lightdm-configuration-greeters config)))))
+
 (define %lightdm-accounts
   (list (user-group (name "lightdm") (system? #t))
         (user-account
@@ -589,9 +590,7 @@ (define (lightdm-shepherd-service config)
                            "/sbin/lightdm")
             #$@(if (lightdm-configuration-debug? config)
                    #~("--debug")
-                   #~())
-            "--config"
-            #$(lightdm-configuration-file config)))
+                   #~())))
 
   (define lightdm-paths
     (let ((lightdm (lightdm-configuration-lightdm config)))
@@ -601,9 +600,6 @@ (define (lightdm-shepherd-service config)
                  '("/bin" "/sbin" "/libexec"))
          ":")))
 
-  (define greeters-config-dir
-    (lightdm-configuration->greeters-config-dir config))
-
   (define data-dirs
     ;; LightDM itself needs to be in XDG_DATA_DIRS for the accountsservice
     ;; interface it provides to be picked up.  The greeters must also be in
@@ -626,11 +622,7 @@ (define (lightdm-shepherd-service config)
                                   ;; Lightdm needs itself in its PATH.
                                   #:environment-variables
                                   (list
-                                   ;; It knows to look for greeter
-                                   ;; configurations in XDG_CONFIG_DIRS...
-                                   (string-append "XDG_CONFIG_DIRS="
-                                                  #$greeters-config-dir)
-                                   ;; ... and for greeter .desktop files as
+                                   ;; It looks for greeter .desktop files as
                                    ;; well as lightdm accountsservice
                                    ;; interface in XDG_DATA_DIRS.
                                    (string-append "XDG_DATA_DIRS="
@@ -638,6 +630,11 @@ (define (lightdm-shepherd-service config)
                                    (string-append "PATH=" #$lightdm-paths))))
     (stop #~(make-kill-destructor)))))
 
+(define (lightdm-etc-service config)
+  "Return a list of FILES for @var{etc-service-type} to build the
+/etc/lightdm directory using CONFIG"
+  (list `("lightdm" ,(lightdm-configuration-directory config))))
+
 (define lightdm-service-type
   (handle-xorg-configuration
    lightdm-configuration
@@ -666,13 +663,10 @@ (define lightdm-service-type
            ;; https://github.com/NixOS/nixpkgs/issues/45059.
            (service-extension profile-service-type
                               lightdm-configuration->packages)
-           ;; This is needed for the greeter itself to find its configuration,
-           ;; because XDG_CONF_DIRS gets overridden by /etc/profile.
-           (service-extension
-            etc-service-type
-            (lambda (config)
-              `(("lightdm"
-                 ,(lightdm-configuration->greeters-config-dir config)))))))
+           ;; This is needed for lightdm and greeter
+           ;; to find their configuration
+           (service-extension etc-service-type
+                              lightdm-etc-service)))
     (description "Run @code{lightdm}, the LightDM graphical login manager."))))
 
 \f
-- 
2.46.0

bug#73859: [PATCH 0/2] lightdm: Fix empty session list.

[Maxim Cournoyer]

Hi Dariqq,

Dariqq <dariqq@posteo.net> writes:

[...]

> Dariqq (2):
>   gnu: lightdm: Use global sysconfdir.
>   gnu: lightdm-service-type: Add lightdm.conf to /etc/lightdm.

Finally pushed to master (see commits b9d7e15f9f and 3a8e19a61d), after
I had some time to properly review and test it.  I've adjusted the
commit messages a bit, and used this Scheme trick to reuse more of the
install phase arguments:

--8<---------------cut here---------------start------------->8---
               ;; matching tests.
-              (unsetenv "LC_ALL"))))))
+              (unsetenv "LC_ALL")))
+          (replace 'install
+            (lambda* (#:key make-flags #:allow-other-keys #:rest args)
+              ;; Override the sysconfdir flag only for the installation phase,
+              ;; as it attempts to write the sample config files to /etc and
+              ;; fail otherwise.
+              (define make-flags*
+                (append make-flags (list (string-append "sysconfdir="
+                                                        #$output "/etc"))))
+              (apply (assoc-ref %standard-phases 'install)
+                     (append args (list #:make-flags make-flags*))))))))
     (inputs
--8<---------------cut here---------------end--------------->8---

Closing.

-- 
Thanks,
Maxim