Update the suffix of the backed up files

Add %M%S to the suffix of the backed-up files in order to prevent accidental overwrite.

tools/db_bk.sh

@@ -13,8 +13,8 @@
 
 DBname=$1
 LogFile=${backup_dir}/db.log
-DumpFile=${backup_dir}/DB_${DBname}_$(date +%Y%m%d_%H).sql
-NewFile=${backup_dir}/DB_${DBname}_$(date +%Y%m%d_%H).tgz
+DumpFile=${backup_dir}/DB_${DBname}_$(date +%Y%m%d_%H%M%S).sql
+NewFile=${backup_dir}/DB_${DBname}_$(date +%Y%m%d_%H%M%S).tgz
 OldFile=${backup_dir}/DB_${DBname}_$(date +%Y%m%d --date="${expired_days} days ago")*.tgz
 
 [ ! -e "${backup_dir}" ] && mkdir -p ${backup_dir}