Add log function to backup script:

roles/terraria/templates/backup.sh

@@ -13,6 +13,12 @@ export TERRARIADIR="{{ terraria_root }}/{{ terraria_name }}"
 export OUTDIR="$TERRARIADIR/backups"
 retention=144 # 30-minute intervals, 3 days
 
+# Helper functions
+log() {
+	[ -z "$1" ] && return 1
+	printf "$(date -Iseconds): $1\n"
+}
+
 # Sanity checks
 if ! [ -d "$OUTDIR" ]; then
 	if ! mkdir "$OUTDIR"; then