diff --git a/NixOS.md b/NixOS.md
index 636b3e6..560678c 100644
--- a/NixOS.md
+++ b/NixOS.md
@@ -21,8 +21,8 @@ This document contains general notes about NixOS that are independent of my NixO
   * [Nix profiles](#nix-profiles)
     * [Switch to previous system profile](#switch-to-previous-system-profile)
     * [List system profiles](#list-system-profiles)
-    * [Garbage collection - Keep most recent X system profiles](#garbage-collection---keep-most-recent-x-system-profiles)
-    * [Garbage collection - Delete system profiles older than X days](#garbage-collection---delete-system-profiles-older-than-x-days)
+    * [Deleting generations - Keep most recent X system profiles](#deleting-generations---keep-most-recent-x-system-profiles)
+    * [Garbage collection - Delete unreachable store objects](#garbage-collection---delete-unreachable-store-objects)
     * [why-depends: Why is a package/dependency installed](#why-depends-why-is-a-packagedependency-installed)
     * [Compare two system profiles](#compare-two-system-profiles)
   * [NixOS configuration debugging](#nixos-configuration-debugging)
@@ -448,33 +448,24 @@ sudo reboot
 
 ### List system profiles
 
-Not sure why 432 is marked as current. It is the default generation that gets activated on next boot. The currently active generation is, however, 429.
-
 ```shell
 sudo nix-env --list-generations --profile /nix/var/nix/profiles/system
 ```
 ```console
 ...
- 428   2024-03-06 12:37:56   
- 429   2024-03-07 11:27:20   
- 430   2024-03-10 12:48:34   
- 431   2024-03-11 11:18:57   
- 432   2024-03-12 22:19:53   (current)
+ 282   2024-11-10 12:53:25   
+ 283   2024-11-11 10:45:46   (current)
 ```
 
 ```shell
 ls -l /nix/var/nix/profiles/
 ```
 ```console
-lrwxrwxrwx 1 root root 43 Dez 14 12:21 default -> /nix/var/nix/profiles/per-user/root/profile
-drwxr-xr-x 1 root root 16 Sep  1  2023 per-user
-lrwxrwxrwx 1 root root 15 Mär 12 22:19 system -> system-432-link
-...
-lrwxrwxrwx 1 root root 77 Mär  6 12:37 system-428-link -> /nix/store/damngdyial0i96xa46csdqk36j2njavi-nixos-system-yodaTux-23.11pre-git
-lrwxrwxrwx 1 root root 77 Mär  7 11:27 system-429-link -> /nix/store/k7c7576sz868gzjci1z6l6nzmdnpd6xr-nixos-system-yodaTux-23.11pre-git
-lrwxrwxrwx 1 root root 77 Mär 10 12:48 system-430-link -> /nix/store/7468m7rgk425kb23aq222a498ynfqdkc-nixos-system-yodaTux-23.11pre-git
-lrwxrwxrwx 1 root root 77 Mär 11 11:18 system-431-link -> /nix/store/r51yw36ddfxq8hdsz2mm6axpbqvjaigy-nixos-system-yodaTux-23.11pre-git
-lrwxrwxrwx 1 root root 77 Mär 12 22:19 system-432-link -> /nix/store/i9pxh3ax6m0yr7xlk7y7c5xdzp74xqi4-nixos-system-yodaTux-23.11pre-git
+lrwxrwxrwx 1 root root 43 Dez 26  2023 default -> /nix/var/nix/profiles/per-user/root/profile
+drwxr-xr-x 1 root root 16 Aug 15  2023 per-user
+lrwxrwxrwx 1 root root 15 Nov 11 10:45 system -> system-283-link
+lrwxrwxrwx 1 root root 77 Nov 10 12:53 system-282-link -> /nix/store/jb5krdbbylwwgvxiadiv6fxja2zgc4h3-nixos-system-yodaTab-24.05pre-git
+lrwxrwxrwx 1 root root 77 Nov 11 10:45 system-283-link -> /nix/store/jf7ml8jzxrmg9djhfr8szq2f19hxysn5-nixos-system-yodaTab-24.05pre-git
 ```
 
 The currently running system. This is the currently active generation. By comparing the store path with the above output, we see that it matches generation 429.
@@ -483,33 +474,45 @@ The currently running system. This is the currently active generation. By compar
 ls -l /run/current-system
 ```
 ```console
-lrwxrwxrwx 1 root root 77 Mär  9 12:44 /run/current-system -> /nix/store/k7c7576sz868gzjci1z6l6nzmdnpd6xr-nixos-system-yodaTux-23.11pre-git
+lrwxrwxrwx 1 root root 77 Nov 11 10:46 /run/current-system -> /nix/store/jf7ml8jzxrmg9djhfr8szq2f19hxysn5-nixos-system-yodaTab-24.05pre-git
 ```
 
-### Garbage collection - Keep most recent X system profiles
+### Deleting generations - Keep most recent X system profiles
 
-A NixOS config example is given in [base.nix](modules/base.nix).
+https://nix.dev/manual/nix/2.18/command-ref/nix-env/delete-generations
+
+> Periodically deleting old generations is important to make garbage collection effective. The is because profiles are also garbage collection roots.
+
+A NixOS config example is given in [nix-gc.nix](modules/nix-gc.nix).
 
 ```shell
 sudo nix-env --delete-generations +7 --profile /nix/var/nix/profiles/system
 ```
 
-TODO: Should we run `sudo nix-collect-garbage --delete-old` after the above?
+After deleting some generations, it is still necessary to collect garbage in order to free up your system. See below.
 
-### Garbage collection - Delete system profiles older than X days
+### Garbage collection - Delete unreachable store objects
+
+https://nix.dev/manual/nix/2.18/command-ref/nix-collect-garbage
+
+> `nix-collect-garbage` deletes all unreachable store objects in the Nix store to clean up your system.
 
 * https://nixos.org/manual/nix/stable/package-management/garbage-collection.html
 * https://discourse.nixos.org/t/why-doesnt-nix-collect-garbage-remove-old-generations-from-efi-menu/17592/4
 
-A NixOS config example is given in [base.nix](modules/base.nix).
-
-Run manually for all profiles:
+First delete unreachable store objects:
 
 ```shell
-sudo nix-collect-garbage --delete-older-than 14d
+# Delete unreachable store objects
+sudo nix-collect-garbage
+
+# Deletes all except the currently active generation prior to deleting unreachable store objects
+#sudo nix-collect-garbage --delete-old
+# Deletes all generations older than 14d prior to deleting unreachable store objects
+#sudo nix-collect-garbage --delete-older-than 14d
 ```
 
-Remove leftover EFI entries of removed generations:
+Then remove leftover EFI entries of deleted generations:
 
 ```shell
 sudo /run/current-system/bin/switch-to-configuration boot
diff --git a/modules/nix-gc.nix b/modules/nix-gc.nix
index a9c8e7b..93c3454 100644
--- a/modules/nix-gc.nix
+++ b/modules/nix-gc.nix
@@ -1,10 +1,11 @@
 { config, pkgs, ... }:
 {
-  # Keep only the 7 most recent system generations.
+  # Delete all system generations except the 7 most recent ones.
+  # Then delete all unreachable store objects.
   #
   # Based on https://github.com/NixOS/nixpkgs/blob/nixos-23.11/nixos/modules/services/misc/nix-gc.nix
-  #
-  # Alternatively: Delete generations older than 7 days
+
+  # Alternative: Delete generations older than 7 days and then delete unreachable store objects
   # https://nixos.wiki/wiki/Storage_optimization#Automation
   #nix.gc = {
   #  automatic = true;
@@ -29,8 +30,10 @@
     };
   };
 
+  # View generated systemd service config with:
+  #   cat "$(systemctl show -P FragmentPath nix-gc-7.service)" | grep ExecStart
   systemd.services."nix-gc-7" = {
-    description = "Keep only the most recent 7 system generations";
+    description = "rm old system generations and unreachable store objects";
 
     conflicts = [ "shutdown.target" "sleep.target" ];
     before = [ "shutdown.target" "sleep.target" ];
@@ -45,6 +48,7 @@
 
     script = ''
       ${config.nix.package.out}/bin/nix-env --delete-generations +7 --profile /nix/var/nix/profiles/system
+      ${config.nix.package.out}/bin/nix-collect-garbage
     '';
   };
 }