From the SMS CLI
In order to perform an SMS backup from the CLI, you have to run the following command at the CLI;
set db.backup = yes.
Setting this attribute to yes creates a local database backup with default options. The default options include the system configuration settings in addition to the most recent Digital Vaccine, TOS package and Custom Package (if installed). This creates a local backup which is placed in the /mgmt/client/tmp directory. In addition this backup file can be downloaded from the Exports and Archives link from the SMS Server home page.