logind: make killUserProcesses an option (#51426)

Right now it's not at all obvious that one can override this option
using `services.logind.extraConfig`; we might as well add an option
for `killUserProcesses` directly so it's clear and documented.

1 files changed, 22 insertions, 3 deletions

diff --git a/nixos/modules/system/boot/systemd.nix b/nixos/modules/system/boot/systemd.nix
index 89f8e81535505..d1029bb579821 100644
--- a/nixos/modules/system/boot/systemd.nix
+++ b/nixos/modules/system/boot/systemd.nix
@@ -601,8 +601,27 @@ in
       type = types.lines;
       example = "IdleAction=lock";
       description = ''
-        Extra config options for systemd-logind. See man logind.conf for
-        available options.
+        Extra config options for systemd-logind. See
+        <link xlink:href="https://www.freedesktop.org/software/systemd/man/logind.conf.html">
+        logind.conf(5)</link> for available options.
+      '';
+    };
+
+    services.logind.killUserProcesses = mkOption {
+      default = false;
+      type = types.bool;
+      description = ''
+        Specifies whether the processes of a user should be killed
+        when the user logs out.  If true, the scope unit corresponding
+        to the session and all processes inside that scope will be
+        terminated.  If false, the scope is "abandoned" (see
+        <link xlink:href="https://www.freedesktop.org/software/systemd/man/systemd.scope.html#">
+        systemd.scope(5)</link>), and processes are not killed.
+        </para>
+
+        <para>
+        See <link xlink:href="https://www.freedesktop.org/software/systemd/man/logind.conf.html#KillUserProcesses=">logind.conf(5)</link>
+        for more details.
       '';
     };
 
@@ -771,7 +790,7 @@ in
 
       "systemd/logind.conf".text = ''
         [Login]
-        KillUserProcesses=no
+        KillUserProcesses=${if config.services.logind.killUserProcesses then "yes" else "no"}
         HandleLidSwitch=${config.services.logind.lidSwitch}
         HandleLidSwitchDocked=${config.services.logind.lidSwitchDocked}
         ${config.services.logind.extraConfig}