add flag to select compression algorithm

lxc-backup.sh

@@ -1,7 +1,7 @@
 #!/usr/bin/env bash
 
 main() {
-  while getopts ":l:d:t:c:h" opt; do
+  while getopts ":l:d:t:x:c:h" opt; do
     case "${opt}" in
       l)
         unset VM_FILTER
@@ -14,6 +14,17 @@ main() {
       t)
         declare -g TARGET="$OPTARG"
         ;;
+      x)
+        declare -g EXTENSION
+        if [[ "${OPTARG,,}" == 'none' ]]; then
+          EXTENTION=""
+        else
+          command -v "$OPTARG" >/dev/null 2>&1 || { echo "$OPTARG command not found"; exit 1; }
+          EXTENTION="${OPTARG,,}"
+        fi
+
+        declare -g COMPRESSION="$OPTARG"
+        ;;
       c)
         declare -g run_cleanup=y
         declare -g files_to_keep="${OPTARG}"
@@ -47,12 +58,13 @@ list_vms() {
 
 usage() {
   cat <<EOF
-Usage: ${0##*/} [-l vm[,vm...]] [-d backup_dir] [-t lxc|incus] [-c <keep n backups>] [-h]
+Usage: ${0##*/} [-l vm[,vm...]] [-d backup_dir] [-t lxc|incus] [-x <compression alogorithm>] [-c <keep n backups>] [-h]
 
 Options:
   -l  Comma-separated list of VMs to back up
   -d  Directory where backups will be stored (default: current directory)
   -t  Manager type: lxc or incus (default: lxc)
+  -x  Compression algorithm (e.g. gzip, zstd, none)
   -c  Cleanup old backups keeping a set number (default: 2)
   -h  Show this message
 
@@ -78,21 +90,23 @@ backup_vms() {
 start_backup() {
   local vm=$1
   local backup_base="$2"
+  local compression="${COMPRESSION:-none}"
+  local ext="${EXTENTION}" ; [[ -n "$ext" ]] && ext=".${ext}"
   local destination="${backup_base}/${vm}"
-  local backup_name="${vm}_$(date +"%Y-%m-%d_%H-%M-%S").tar"
+  local backup_name="${vm}_$(date +"%Y-%m-%d_%H-%M-%S").tar${ext}"
 
   [[ -d "$backup_base" ]] || { echo "${backup_base} is not a directory"; exit 1; }
   [[ -d "$destination" ]] || mkdir "$destination"
   [[ -f "${destination}/${backup_name}" ]] && { echo "Backup already exists"; return 2; }
 
-  lxc export "$vm" --instance-only --compression none "${destination}/${backup_name}" || { echo "Error exporting $vm"; return 1; }
+  lxc export "$vm" --instance-only --compression "${compression}" "${destination}/${backup_name}" || { echo "Error exporting $vm"; return 1; }
 
   [[ -n "$run_cleanup" ]] && prune_backups "$destination"
 }
 
 prune_backups() {
   local backup_directory="$1"
-  mapfile -t backup_files < <(find "$backup_directory" -maxdepth 1 -name "*.tar" -printf '%T@ %p\n' | sort -n | head -n "-${files_to_keep}" | cut -d' ' -f2-)
+  mapfile -t backup_files < <(find "$backup_directory" -maxdepth 1 -type f -printf '%T@ %p\n' | sort -n | head -n "-${files_to_keep}" | cut -d' ' -f2-)
   
   if [[ ${#backup_files[@]} -gt 0 ]]; then
     echo "Removing ${#qcow2_files[@]} old backup files for $vm (keeping last $total_files_to_keep files)"