From d7e56aebec4535f3567c362b6084818873e54b0d Mon Sep 17 00:00:00 2001
From: Maxim Cournoyer <maxim.cournoyer@gmail.com>
Date: Fri, 16 Sep 2022 14:45:15 -0400
Subject: services: desktop: Mount /var/lib/gdm on a tmpfs file system.

Fixes <https://issues.guix.gnu.org/44944>.

* gnu/services/xorg.scm (%gdm-activation): Delete variable.
(gdm-service-type): De-register it.
* gnu/services/desktop.scm (%gdm-file-system): New variable.
(gdm-file-system-service): Likewise.
(desktop-services-for-system): Use it.
---
 gnu/services/desktop.scm | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

(limited to 'gnu/services/desktop.scm')

diff --git a/gnu/services/desktop.scm b/gnu/services/desktop.scm
index 9b3eb12613..1b087635d1 100644
--- a/gnu/services/desktop.scm
+++ b/gnu/services/desktop.scm
@@ -117,6 +117,9 @@ (define-module (gnu services desktop)
             elogind-service
             elogind-service-type
 
+            %gdm-file-system
+            gdm-file-system-service
+
             %fontconfig-file-system
             fontconfig-file-system-service
 
@@ -1232,6 +1235,13 @@ (define %fontconfig-file-system
     (flags '(read-only))
     (check? #f)))
 
+(define %gdm-file-system
+  (file-system
+    (device "none")
+    (mount-point "/var/lib/gdm")
+    (type "tmpfs")
+    (check? #f)))
+
 ;; The global fontconfig cache directory can sometimes contain stale entries,
 ;; possibly referencing fonts that have been GC'd, so mount it read-only.
 ;; As mentioned https://debbugs.gnu.org/cgi/bugreport.cgi?bug=36924#8 and
@@ -1240,6 +1250,15 @@ (define fontconfig-file-system-service
   (simple-service 'fontconfig-file-system
                   file-system-service-type
                   (list %fontconfig-file-system)))
+
+;; Avoid stale caches and stale user IDs being reused between system
+;; reconfigurations, which would crash GDM and render the system unusable.
+;; GDM doesn't require persisting anything valuable there anyway.
+(define gdm-file-system-service
+  (simple-service 'gdm-file-system
+                  file-system-service-type
+                  (list %gdm-file-system)))
+
 
 ;;;
 ;;; AccountsService service.
@@ -1750,6 +1769,10 @@ (define* (desktop-services-for-system #:optional
                               (list (file-append nfs-utils "/sbin/mount.nfs")
                                (file-append ntfs-3g "/sbin/mount.ntfs-3g"))))
 
+         ;; This is a volatile read-write file system mounted at /var/lib/gdm,
+         ;; to avoid GDM stale cache and permission issues.
+         gdm-file-system-service
+
          ;; The global fontconfig cache directory can sometimes contain
          ;; stale entries, possibly referencing fonts that have been GC'd,
          ;; so mount it read-only.
-- 
cgit v1.2.3