From 3952094233f225eac2ed58f679bf77777ecceae8 Mon Sep 17 00:00:00 2001
From: Daniel Langbein <daniel@systemli.org>
Date: Mon, 28 Aug 2023 15:50:16 +0200
Subject: [PATCH] BTRFS swap file

---
 README.md                          | 13 +++++++++++++
 yodaTab/hardware-configuration.nix |  8 +++++++-
 2 files changed, 20 insertions(+), 1 deletion(-)

diff --git a/README.md b/README.md
index af82c9e..62140ff 100644
--- a/README.md
+++ b/README.md
@@ -98,6 +98,19 @@ Use the corresponding branch:
 # TODO (!)
 ```
 
+## BTRFS Swap file
+
+* https://nixos.wiki/wiki/Btrfs#Swap_file
+* https://wiki.archlinux.org/title/btrfs#Swap_file
+
+Summary:
+
+* Create subvolume `@swap` directly below top-level subvolume.
+* Mount at `/swap`
+* Create swapfile: `sudo btrfs filesystem mkswapfile --size 8g --uuid clear /swap/swapfile`
+* Regenerate hardware-configuration: `sudo nixos-generate-config --dir yodaTab`
+* Add `swapDevices = [ { device = "/swap/swapfile"; } ];` to hardware configuration and run `nixos-rebuild switch` (see above).
+
 ## Automount Encrypted Drive
 
 * Generate and add keyfile to LUKS device
diff --git a/yodaTab/hardware-configuration.nix b/yodaTab/hardware-configuration.nix
index 9a387c0..05e62ac 100644
--- a/yodaTab/hardware-configuration.nix
+++ b/yodaTab/hardware-configuration.nix
@@ -35,7 +35,13 @@
 
   boot.initrd.luks.devices."512gb".device = "/dev/disk/by-uuid/03d4ac28-2c81-463e-b615-fb623d40b6fa";
 
-  swapDevices = [ ];
+  fileSystems."/swap" =
+    { device = "/dev/disk/by-uuid/f87e6b3c-12f2-4fda-92b3-06b07bdad58f";
+      fsType = "btrfs";
+      options = [ "subvol=@swap" ];
+    };
+
+  swapDevices = [ { device = "/swap/swapfile"; } ];
 
   # Enables DHCP on each ethernet and wireless interface. In case of scripted networking
   # (the default) this is the recommended approach. When using systemd-networkd it's