making snap-and-mount more maintainable

nixos/modules/nixos/services/zfs-nightly-snap/default.nix

@@ -18,153 +18,7 @@ let
     ];
 
     text = ''
-      # Check if running as root
+      ${builtins.readFile ./snap-and-mount.sh} "${cfg.mountPath}" "${cfg.zfsDataset}" "${cfg.snapshotName}"
-      if [ "$(id -u)" -ne 0 ]; then
-        echo "Error: This script must be run as root."
-        exit 1
-      fi
-
-      BACKUP_DIRECTORY="${cfg.mountPath}"
-      ZFS_DATASET="${cfg.zfsDataset}"
-      SNAPSHOT_NAME="${cfg.snapshotName}"
-
-      # 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 "''${1}" -type d -empty -delete
-      }
-
-      # gets the name of the newest snapshot given a zfs filesystem
-      # usage: get_latest_snap filesystem
-      function zfs_latest_snap() {
-        snapshot=$(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 "''${path}"
-          return 0
-        else
-          return 1
-        fi
-      }
-
-      # mounts latest snapshot in directory
-      # usage: mount_latest_snap filesystem BACKUP_DIRECTORY
-      function mount_latest_snap() {
-        local mount_point="''${2}"
-        local 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 ''${filesystem}, perhaps it's not mounted? Anyways, it will not be backed up."
-          return 1
-        fi
-
-        # mountpath may be inside a previously mounted snapshot
-        mountpath="$mount_point/''${filesystem}"
-
-        # mount to backup directory using a bind filesystem
-        mkdir -p "''${mountpath}"
-        echo "mount ''${sourcepath} => ''${mountpath}"
-        mount --bind --read-only "''${sourcepath}" "''${mountpath}"
-        return 0
-      }
-
-      # Unmount and cleanup if necessary
-      zfs_backup_cleanup "$BACKUP_DIRECTORY"
-
-      # Check if snapshot exists
-      echo "Previous snapshot:"
-      zfs list -t snapshot | grep "$ZFS_DATASET@$SNAPSHOT_NAME" || true
-
-      # Attempt to destroy existing snapshot
-      echo "Attempting to destroy existing snapshot..."
-      if zfs list -t snapshot | grep -q "$ZFS_DATASET@$SNAPSHOT_NAME"; then
-        if zfs destroy -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then
-          echo "Successfully destroyed old snapshot"
-        else
-          echo "Failed to destroy existing snapshot"
-          exit 1
-        fi
-      else
-        echo "No existing snapshot found"
-      fi
-
-      # Create new snapshot
-      if ! zfs snapshot -r "$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"
-
-      # Mount the snapshot
-      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

nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount-standalone.sh

@@ -0,0 +1,15 @@
+#!/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"

nixos/modules/nixos/services/zfs-nightly-snap/snap-and-mount.sh

@@ -1,14 +1,16 @@
-#!/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
+# Command line arguments
-
+BACKUP_DIRECTORY="$1"
-BACKUP_DIRECTORY="/mnt/restic_nightly_backup"
+ZFS_DATASET="$2"
-ZFS_DATASET="nahar/containers/volumes"
+SNAPSHOT_NAME="$3"
-SNAPSHOT_NAME="restic_nightly_snap"
 
+if [ -z "$BACKUP_DIRECTORY" ] || [ -z "$ZFS_DATASET" ] || [ -z "$SNAPSHOT_NAME" ]; then
+  echo "Usage: $0 <backup_directory> <zfs_dataset> <snapshot_name>"
+  exit 1
+fi
 # Check if running as root
+
 if [ "$(id -u)" -ne 0 ]; then
   echo "Error: This script must be run as root."
   exit 1
@@ -19,7 +21,7 @@ fi
 # mounts all zfs filesystems under $ZFS_DATASET
 function mount_dataset() {
   # ensure BACKUP_DIRECTORY exists
-  mkdir -p $BACKUP_DIRECTORY
+  mkdir -p "$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)
@@ -44,7 +46,7 @@ function zfs_backup_cleanup() {
   done
 
   # delete empty directories from within the backup directory
-  find "${1}" -type d -empty -delete
+  find "${1}" -type d -empty -delete 2>/dev/null || true
 }
 
 # gets the name of the newest snapshot given a zfs filesystem
@@ -123,16 +125,12 @@ zfs list -t snapshot | grep "$ZFS_DATASET@$SNAPSHOT_NAME" || true
 
 # Attempt to destroy existing snapshot
 echo "Attempting to destroy existing snapshot..."
-if zfs list -t snapshot | grep -q "$ZFS_DATASET@$SNAPSHOT_NAME"; then
 if zfs destroy -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then
   echo "Successfully destroyed old snapshot"
 else
   echo "Failed to destroy existing snapshot"
   exit 1
 fi
-else
-  echo "No existing snapshot found"
-fi
 
 # Create new snapshot
 if ! zfs snapshot -r "$ZFS_DATASET@$SNAPSHOT_NAME"; then