You can prepare a Day 0 configuration file before you launch the ASAv. This file is a text file that contains the ASAv configuration
applied when the ASAv is launched. This initial configuration is placed into a text file named “day0-config” in a working
directory you chose, and is manipulated into a day0.iso file that is mounted and read on first boot. At the minimum, the Day
0 configuration file must contain commands to activate the management interface and set up the SSH server for public key authentication,
but it can also contain a complete ASA configuration.
The day0.iso file (either your custom day0.iso or the default day0.iso) must be available during first boot:
To automatically license the ASAv during initial deployment, place the Smart Licensing Identity (ID) Token that you downloaded
from the Cisco Smart Software Manager in a text file named ‘idtoken’ in the same directory as the Day 0 configuration file.
If you want to deploy the ASAv in transparent mode, you must use a known running ASA config file in transparent mode as the
Day 0 configuration file. This does not apply to a Day 0 configuration file for a routed firewall.
We are using Linux in this example, but there are similar utilities for Windows.