Performance: How Fast is sdm?

I timed how long it took to build my personal IMG from a "stock" RasPiOS Bullseye IMG. Times rounded to the closest minute. The Lite customization takes longer because I install XWindows, xdm, icewm, xterm, chromium-browser, firefox, and everything that those apps pull in, as opposed to the "with Desktop" system which doesn't need to install XWindows, the display manager, and window manager, since they're already installed.

• Running RasPiOS on an SD Card and customizing an IMG located locally on that SD card
  • RasPiOS with Desktop: 7m
  • RasPiOS Lite: 9m
• Running RasPiOS on an SSD and customizing an IMG located on an NFS-mounted SSD
  • RasPiOS with Desktop: 5m
  • RasPiOS Lite: 6m
• Running RasPiOS on an SSD and customizing an IMG located locally on that SSD
  • RasPiOS with Desktop: 4m
  • RasPiOS Lite: 5m

Burning RasPiOS Lite with --expand-root to an SSD and booting it:

• 00:00:00 Start burn to SSD
• 00:01:15 Burn complete
• 00:01:45 Power on Pi. System boots and among other things runs the sdm FirstBoot script
• 00:02:52 System automatically reboots via sdm FirstBoot script
• 00:03:26 System at command prompt ready to login

You read that correctly...In less than 20 minutes, you can go from a "stock" RasPiOS IMG to having your own customized system booted and ready to go.

But, if you keep your customized image around, you can have a freshly-made system booted and ready to go in less than 5 minutes. With all your customizations already in place.