Once you install BSDRP, FreeBSD ports repository is not enabled, the root-partition is read-only and /var is to small to download and extract the database.

• make sure you have extended the data slice
• mount / as rw: mount -uw /
• extend /var and /etc via /conf/base/etc/md_size and /conf/base/var/md_size (122880 for 60MB)
• mount / as ro: mount -ur /
• reboot: If you are asked to save your config, choose “No”
• enable the FreeBSD repo and disable the local repo in /usr/local/etc/pkg/repos/myrepo.conf
• pkg update
• for installing a package, you have to mount / writeable again: mount -uw /
• now you can install your package: pkg install <package>
• done!

• https://bsdrp.net/documentation/technical_docs#how_to_modify_an_existing_image
• https://sourceforge.net/p/bsdrp/mailman/message/34065870/