Snipe-IT comes with a GUI-based and command line based backup utility. You can generate or download a backup in Admin > Backups through the web interface:

... or you can use the command line tool:

The Snipe-IT Backup utility will create a SQL dump of your database along with any images or file attachments you have uploaded, and zip them up with a timestamp.

For information on automating these backups to run periodically, see the documentation on configuring alerts and backups.