My firewall is a ALIX2D13 with pfsense. And, shame on me, I was still running pfsense 2.1.5.
I don’t have to work today, so, time to upgrade.

Before starting the upgrade process, I opened the case of my ALIX2D13 and removed the CF-card.

Then, I’ve put the CF card in a USB card reader to make a backup with ‘dd’. Just to be safe, in case the upgrade process fails, I can easily switch back to the old version.

After the backup was ready, I’ve started the upgrade process, which worked without any problems. Finally my firewall is back up to date :-)