From 23c70023685bfec26d8c3cbb1451259ce163b105 Mon Sep 17 00:00:00 2001
From: magic_rb <richard@brezak.sk>
Date: Wed, 18 Oct 2023 14:30:17 +0200
Subject: [PATCH] Mount old versions of home on omen

Signed-off-by: magic_rb <richard@brezak.sk>
---
 nixos/systems/omen/impermenance.nix            | 16 ++++++++++++++++
 overlays/rolling_datasets/bin/mount_datasets   | 18 ++++++++++++++++++
 overlays/rolling_datasets/bin/roll_dataset     |  2 ++
 overlays/rolling_datasets/default.nix          |  6 +++++-
 .../functions/get_old_datasets                 |  2 +-
 5 files changed, 42 insertions(+), 2 deletions(-)
 create mode 100644 overlays/rolling_datasets/bin/mount_datasets

diff --git a/nixos/systems/omen/impermenance.nix b/nixos/systems/omen/impermenance.nix
index b806093..5862695 100644
--- a/nixos/systems/omen/impermenance.nix
+++ b/nixos/systems/omen/impermenance.nix
@@ -85,6 +85,22 @@
     '';
   };
 
+  systemd.services."mount-old-homes" = {
+    description = "Mount old versions of home dataset";
+
+    wantedBy = [ "local-fs.target" ];
+    after = [ "local-fs.target" ];
+
+    script = ''
+      ${pkgs.rolling_datasets}/bin/mount_datasets "omen-ssd/ephemeral/home" "/home/.old"
+    '';
+
+    serviceConfig = {
+      Type = "oneshot";
+      RemainAfterExit = "yes";
+      TimeoutStartSec = "5m";
+    };
+  };
 
   systemd.services."home-manager-main-pre.service" = {
     description = "Home Manager environment prestart for main";
diff --git a/overlays/rolling_datasets/bin/mount_datasets b/overlays/rolling_datasets/bin/mount_datasets
new file mode 100644
index 0000000..1044465
--- /dev/null
+++ b/overlays/rolling_datasets/bin/mount_datasets
@@ -0,0 +1,18 @@
+# -*- mode: shell-script -*-
+
+source @out@/share/functions/get_old_datasets
+
+export "PATH=$PATH:@runtimePath@"
+
+if [[ "$#" != 2 ]] ; then
+    echo "This script requires precisely 2 arguments!"
+    exit 1
+fi
+
+dataset="$1"
+mountpoint="$2"
+
+while IFS="\n" read gen
+do
+    mountpoint -q "$mountpoint/$gen" || mount -o x-mount.mkdir -v -t zfs "$dataset/$gen" "$mountpoint/$gen"
+done <<< "$(get_old_datasets "$dataset")"
diff --git a/overlays/rolling_datasets/bin/roll_dataset b/overlays/rolling_datasets/bin/roll_dataset
index d117df0..2ba7cfc 100644
--- a/overlays/rolling_datasets/bin/roll_dataset
+++ b/overlays/rolling_datasets/bin/roll_dataset
@@ -2,6 +2,8 @@
 
 source @out@/share/functions/get_old_datasets
 
+export "PATH=$PATH:@runtimePath@"
+
 if [[ "$#" != 3 ]] ; then
     echo "This script requires precisely 2 arguments!"
     exit 1
diff --git a/overlays/rolling_datasets/default.nix b/overlays/rolling_datasets/default.nix
index 60017fd..aded02a 100644
--- a/overlays/rolling_datasets/default.nix
+++ b/overlays/rolling_datasets/default.nix
@@ -53,9 +53,13 @@
           } ''
             mkdir -p $out/bin
             mkdir -p $out/share/functions
+            export runtimeShell=${prev.runtimeShell} \
+                   runtimePath=${prev.lib.makeBinPath (with prev; [ utillinux zfs ])}
 
             for binary in ${./bin}/* ; do
-              substituteAll "$binary" "$out/bin/$(basename "$binary")"
+              output_binary="$out/bin/$(basename "$binary")"
+              substituteAll "$binary" "$output_binary"
+              chmod +x "$output_binary"
             done
 
             for function in ${./functions}/* ; do
diff --git a/overlays/rolling_datasets/functions/get_old_datasets b/overlays/rolling_datasets/functions/get_old_datasets
index 836abea..64ad3d5 100644
--- a/overlays/rolling_datasets/functions/get_old_datasets
+++ b/overlays/rolling_datasets/functions/get_old_datasets
@@ -2,5 +2,5 @@
 function get_old_datasets()
 {
   dataset="$1"
-  zfs list "$dataset" -t filesystem -r -H -o name | xargs -I {} ${final.runtimeShell} -c 'echo "$1" | rev | cut -f 1 -d "/" | rev' sh {} | grep -v "$dataset"
+  zfs list "$dataset" -t filesystem -r -H -o name | xargs -I {} @runtimeShell@ -c 'echo "$1" | rev | cut -f 1 -d "/" | rev' sh {} | grep -v "$(basename "$dataset")"
 }