From 4f5c090534f5f9fc0b9930a136efdc2e29dc567f Mon Sep 17 00:00:00 2001
From: Joseph Hanson <joe@veri.dev>
Date: Sat, 4 Jan 2025 19:17:53 -0600
Subject: [PATCH] snap and mount separation

---
 .../services/zfs-nightly-snap/default.nix     |  43 +++++-
 .../services/zfs-nightly-snap/functions.sh    |  68 ++++++++++
 .../snap-and-mount-standalone.sh              |  15 ---
 .../zfs-nightly-snap/snap-and-mount.sh        | 124 ++----------------
 4 files changed, 120 insertions(+), 130 deletions(-)
 create mode 100644 nixos/modules/nixos/services/zfs-nightly-snap/functions.sh
 delete mode 100755 nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount-standalone.sh
 mode change 100644 => 100755 nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount.sh

diff --git a/nixos/modules/nixos/services/zfs-nightly-snap/default.nix b/nixos/modules/nixos/services/zfs-nightly-snap/default.nix
index 96a034e..85c2417 100644
--- a/nixos/modules/nixos/services/zfs-nightly-snap/default.nix
+++ b/nixos/modules/nixos/services/zfs-nightly-snap/default.nix
@@ -18,7 +18,48 @@ let
     ];
 
     text = ''
-      ${builtins.readFile ./snap-and-mount.sh} "${cfg.mountPath}" "${cfg.zfsDataset}" "${cfg.snapshotName}"
+      # Import our functions
+      ${builtins.readFile ./functions.sh}
+
+      BACKUP_DIRECTORY="${cfg.mountPath}"
+      ZFS_DATASET="${cfg.zfsDataset}"
+      SNAPSHOT_NAME="${cfg.snapshotName}"
+
+      if [ "$(id -u)" -ne 0 ]; then
+        echo "Error: This script must be run as root."
+        exit 1
+      fi
+
+      # Main logic
+      zfs_backup_cleanup "$BACKUP_DIRECTORY"
+
+      echo "Previous snapshot:"
+      zfs list -t snapshot | grep "$ZFS_DATASET@$SNAPSHOT_NAME" || true
+
+      echo "Attempting to destroy existing snapshot..."
+      if zfs destroy -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then
+        echo "Successfully destroyed old snapshot"
+      else
+        echo "Failed to destroy existing snapshot"
+        exit 1
+      fi
+
+      # Create new snapshot
+      if ! zfs snapshot -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then
+        echo "Failed to create snapshot"
+        exit 1
+      fi
+
+      echo "New snapshot created:"
+      zfs list -t snapshot | grep "$ZFS_DATASET@$SNAPSHOT_NAME"
+
+      if ! mount_dataset; then
+        echo "Failed to mount snapshot"
+        exit 1
+      fi
+
+      echo "Successfully created and mounted snapshot at $BACKUP_DIRECTORY"
+      mount | grep "$BACKUP_DIRECTORY"
     '';
   };
 in
diff --git a/nixos/modules/nixos/services/zfs-nightly-snap/functions.sh b/nixos/modules/nixos/services/zfs-nightly-snap/functions.sh
new file mode 100644
index 0000000..54f7cfd
--- /dev/null
+++ b/nixos/modules/nixos/services/zfs-nightly-snap/functions.sh
@@ -0,0 +1,68 @@
+#!/usr/bin/env bash
+
+# functions sourced from: https://github.com/Jip-Hop/zfs-backup-snapshots
+function mount_dataset() {
+  mkdir -p "$BACKUP_DIRECTORY"
+  mapfile -t fs < <(zfs list "$ZFS_DATASET" -r -H -o name,mountpoint | grep -E "(legacy)$|(none)$" -v | awk '{print gsub("/","/", $2), $1}' | sort -n | cut -d' ' -f2-)
+
+  for fs in "${fs[@]}"; do
+    mount_latest_snap "${fs}" "${BACKUP_DIRECTORY}"
+  done
+  return 0
+}
+
+function zfs_backup_cleanup() {
+  mapfile -t fs < <(tac /etc/mtab | cut -d " " -f 2 | grep "${1}")
+
+  for i in "${fs[@]}"; do
+    echo "Unmounting $i"
+    umount "$i"
+  done
+
+  find "${1}" -type d -empty -delete 2>/dev/null || true
+}
+
+function zfs_latest_snap() {
+  snapshot=$(zfs list -H -t snapshot -o name -S creation -d1 "${1}" | head -1 | cut -d '@' -f 2)
+  if [[ -z $snapshot ]]; then
+    echo "No snapshot exists for ${1}, it will not be backed up."
+    return 1
+  fi
+  echo "$snapshot"
+}
+
+function zfs_snapshot_mountpoint() {
+  mountpoint=$(zfs list -H -o mountpoint "${1}")
+  if [[ $? == 1 ]]; then
+    return 1
+  fi
+  path="${mountpoint}/.zfs/snapshot/${2}"
+  if stat "${path}" &>/dev/null; then
+    echo "${path}"
+    return 0
+  else
+    return 1
+  fi
+}
+
+function mount_latest_snap() {
+  BACKUP_DIRECTORY="${2}"
+  filesystem="${1}"
+
+  snapshot=$(zfs_latest_snap "${filesystem}")
+  if [[ $? == 1 ]]; then
+    return 1
+  fi
+
+  sourcepath=$(zfs_snapshot_mountpoint "${filesystem}" "${snapshot}")
+  if [[ $? == 1 ]]; then
+    echo "Cannot find snapshot ${snapshot} for ${filesystem}, perhaps it's not mounted?"
+    return 1
+  fi
+
+  mountpath=${BACKUP_DIRECTORY}/${filesystem}
+  mkdir -p "${mountpath}"
+  echo "mount ${sourcepath} => ${mountpath}"
+  mount --bind --read-only "${sourcepath}" "${mountpath}"
+  return 0
+}
diff --git a/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount-standalone.sh b/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount-standalone.sh
deleted file mode 100755
index 002775b..0000000
--- a/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount-standalone.sh
+++ /dev/null
@@ -1,15 +0,0 @@
-#!/usr/bin/env nix-shell
-#!nix-shell -I nixpkgs=/etc/nix/inputs/nixpkgs -i bash -p busybox zfs
-# shellcheck disable=SC1008
-
-set -e # Exit on error
-
-BACKUP_DIRECTORY="/mnt/restic_nightly_backup"
-ZFS_DATASET="nahar/containers/volumes"
-SNAPSHOT_NAME="restic_nightly_snap"
-
-# Execute the main script with our parameters
-./snap-and-mount.sh \
-  "$BACKUP_DIRECTORY" \
-  "$ZFS_DATASET" \
-  "$SNAPSHOT_NAME"
diff --git a/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount.sh b/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount.sh
old mode 100644
new mode 100755
index 030f769..850a751
--- a/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount.sh
+++ b/nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount.sh
@@ -1,129 +1,27 @@
+#!/usr/bin/env nix-shell
+#!nix-shell -I nixpkgs=/etc/nix/inputs/nixpkgs -i bash -p busybox zfs
 # shellcheck disable=SC1008
 
-# Command line arguments
-BACKUP_DIRECTORY="$1"
-ZFS_DATASET="$2"
-SNAPSHOT_NAME="$3"
+set -e # Exit on error
 
-if [ -z "$BACKUP_DIRECTORY" ] || [ -z "$ZFS_DATASET" ] || [ -z "$SNAPSHOT_NAME" ]; then
-  echo "Usage: $0 <backup_directory> <zfs_dataset> <snapshot_name>"
-  exit 1
-fi
-# Check if running as root
+# Source the functions
+. ./functions.sh
+
+BACKUP_DIRECTORY="${1:-/mnt/restic_nightly_backup}"
+ZFS_DATASET="${2:-nahar/containers/volumes}"
+SNAPSHOT_NAME="${3:-restic_nightly_snap}"
 
 if [ "$(id -u)" -ne 0 ]; then
   echo "Error: This script must be run as root."
   exit 1
 fi
 
-# functions sourced from: https://github.com/Jip-Hop/zfs-backup-snapshots
-# some enhancements made to the original code to adhere to best practices
-# mounts all zfs filesystems under $ZFS_DATASET
-function mount_dataset() {
-  # ensure BACKUP_DIRECTORY exists
-  mkdir -p "$BACKUP_DIRECTORY"
-  # get list of all zfs filesystems under $ZFS_DATASET
-  # exclude if mountpoint "legacy" and "none" mountpoint
-  # order by shallowest mountpoint first (determined by number of slashes)
-  mapfile -t fs < <(zfs list "$ZFS_DATASET" -r -H -o name,mountpoint | grep -E "(legacy)$|(none)$" -v | awk '{print gsub("/","/", $2), $1}' | sort -n | cut -d' ' -f2-)
-
-  for fs in "${fs[@]}"; do
-    mount_latest_snap "${fs}" "${BACKUP_DIRECTORY}"
-  done
-  return 0
-}
-
-# umounts and cleans up the backup directory
-# usage: zfs_backup_cleanup BACKUP_DIRECTORY
-function zfs_backup_cleanup() {
-  # get all filesystems mounted within the backup directory
-  mapfile -t fs < <(tac /etc/mtab | cut -d " " -f 2 | grep "${1}")
-
-  # umount said filesystems
-  for i in "${fs[@]}"; do
-    echo "Unmounting $i"
-    umount "$i"
-  done
-
-  # delete empty directories from within the backup directory
-  find "${1}" -type d -empty -delete 2>/dev/null || true
-}
-
-# gets the name of the newest snapshot given a zfs filesystem
-# usage: get_latest_snap filesystem
-function zfs_latest_snap() {
-  snapshot=$(zfs list -H -t snapshot -o name -S creation -d1 "${1}" | head -1 | cut -d '@' -f 2)
-  if [[ -z $snapshot ]]; then
-    # if there's no snapshot then let's ignore it
-    echo "No snapshot exists for ${1}, it will not be backed up."
-    return 1
-  fi
-  echo "$snapshot"
-}
-
-# gets the path of a snapshot given a zfs filesystem and a snapshot name
-# usage zfs_snapshot_mountpoint filesystem snapshot
-function zfs_snapshot_mountpoint() {
-  # get mountpoint for filesystem
-  mountpoint=$(zfs list -H -o mountpoint "${1}")
-
-  # exit if filesystem doesn't exist
-  if [[ $? == 1 ]]; then
-    return 1
-  fi
-
-  # build out path
-  path="${mountpoint}/.zfs/snapshot/${2}"
-
-  # check to make sure path exists
-  if stat "${path}" &>/dev/null; then
-    echo "${path}"
-    return 0
-  else
-    return 1
-  fi
-}
-
-# mounts latest snapshot in directory
-# usage: mount_latest_snap filesystem BACKUP_DIRECTORY
-function mount_latest_snap() {
-  BACKUP_DIRECTORY="${2}"
-  filesystem="${1}"
-
-  # get name of latest snapshot
-  snapshot=$(zfs_latest_snap "${filesystem}")
-
-  # if there's no snapshot then let's ignore it
-  if [[ $? == 1 ]]; then
-    echo "No snapshot exists for ${filesystem}, it will not be backed up."
-    return 1
-  fi
-
-  sourcepath=$(zfs_snapshot_mountpoint "${filesystem}" "${snapshot}")
-  # if the filesystem is not mounted/path doesn't exist then let's ignore as well
-  if [[ $? == 1 ]]; then
-    echo "Cannot find snapshot ${snapshot} for ${filesystem}, perhaps it's not mounted? Anyways, it will not be backed up."
-    return 1
-  fi
-
-  # mountpath may be inside a previously mounted snapshot
-  mountpath=${BACKUP_DIRECTORY}/${filesystem}
-
-  # mount to backup directory using a bind filesystem
-  mkdir -p "${mountpath}"
-  echo "mount ${sourcepath} => ${mountpath}"
-  mount --bind --read-only "${sourcepath}" "${mountpath}"
-  return 0
-}
-
-# Unmount and cleanup if necessary
+# Main logic
 zfs_backup_cleanup "$BACKUP_DIRECTORY"
 
-# Check if snapshot exists
 echo "Previous snapshot:"
 zfs list -t snapshot | grep "$ZFS_DATASET@$SNAPSHOT_NAME" || true
 
-# Attempt to destroy existing snapshot
 echo "Attempting to destroy existing snapshot..."
 if zfs destroy -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then
   echo "Successfully destroyed old snapshot"
@@ -132,7 +30,6 @@ else
   exit 1
 fi
 
-# Create new snapshot
 if ! zfs snapshot -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then
   echo "Failed to create snapshot"
   exit 1
@@ -141,7 +38,6 @@ fi
 echo "New snapshot created:"
 zfs list -t snapshot | grep "$ZFS_DATASET@$SNAPSHOT_NAME"
 
-# Mount the snapshot
 if ! mount_dataset; then
   echo "Failed to mount snapshot"
   exit 1