updated

slides/slides.md

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+```txt
+/nix            /                       /persist
+            +------------------------+
+  /store/x -|-> /var/x               |
+            |   /var/lib/bluetooth <-|-   /var/lib/bluetooth
+  /store/y -|-> /bin/y               |
+            |   /home/admin/.local <-|-   /home/admin/.local
+  /store/z -|-> /etc/z               |
+            +------------------------+
+```
+
+```nix
+{...}: {
+  boot.initrd.postDeviceCommands = lib.mkAfter ''
+    mkdir /btrfs_tmp
+    mount /dev/mapper/crypted /btrfs_tmp
+    if [[ -e /btrfs_tmp/root ]]; then
+        mkdir -p /btrfs_tmp/old_roots
+        timestamp=$(date --date="@$(stat -c %Y /btrfs_tmp/root)" "+%Y-%m-%-d_%H:%M:%S")
+        mv /btrfs_tmp/root "/btrfs_tmp/old_roots/$timestamp"
+    fi
+
+    delete_subvolume_recursively() {
+        IFS=$'\n'
+        for i in $(btrfs subvolume list -o "$1" | cut -f 9- -d ' '); do
+            delete_subvolume_recursively "/btrfs_tmp/$i"
+        done
+        btrfs subvolume delete "$1"
+    }
+
+    for i in $(find /btrfs_tmp/old_roots/ -maxdepth 1 -mtime +30); do
+        delete_subvolume_recursively "$i"
+    done
+
+    btrfs subvolume create /btrfs_tmp/root
+    umount /btrfs_tmp
+  '';
+}
+```
+
+```nix
+{
+  inputs = {
+    impermanence = {
+      url = "github:nix-community/impermanence";
+    };
+  };
+
+  outputs = {self, ...} @ inputs: let
+    system = "x86_64-linux";
+    pkgs = inputs.nixpkgs.legacyPackages.${system};
+  in {
+    nixosConfigurations = {
+      default = inputs.nixpkgs.lib.nixosSystem {
+        inherit system;
+
+        modules = [
+          inputs.impermanence.nixosModules.impermanence
+          ...
+        ];
+      };
+    };
+  }
+}
+```
+
+```nix
+{...}: {
+  fileSystems."/persist".neededForBoot = true;
+  environment.persistence."/persist" = {
+    hideMounts = true;
+    directories = [
+      {
+        directory = "/etc/nixos";
+        user = "demo";
+        mode = "u=rwx,g=rx,o=rx";
+      }
+      "/var/log"
+      "/var/lib/bluetooth"
+      "/var/lib/nixos"
+      "/var/lib/systemd/coredump"
+      "/etc/NetworkManager/system-connections"
+    ];
+    files = [
+      "/etc/machine-id"
+      {
+        file = "/var/keys/secret_file";
+        parentDirectory = {mode = "u=rwx,g=,o=";};
+      }
+    ];
+
+    users."demo" = {
+      directories = [
+        "this-will-persist"
+      ];
+    };
+  };
+}
+```