Preparing the uSD card
----------------------
First let's write the armv7.img to the uSD card:
 
 # dd if=armv7.img of=/dev/rsd0 bs=1m conv=sync
 1757+1 records in
 1758+0 records out
 1843396608 bytes transferred in 147.701 secs (12480596 bytes/sec)

After that we need to install the u-boot for the corresponding board,
e.g. for a banana-pi:

 # dd if=/usr/pkg/share/u-boot/bananapi/u-boot-sunxi-with-spl.bin of=/dev/rsd0 bs=1k seek=8 conv=sync
 422+1 records in
 423+0 records out
 433152 bytes transferred in 0.322 secs (1345192 bytes/sec)

By default disklabel is adjusted so that `/' can grow to take all the
free space in the uSD card.
To avoid that we can set in rc.conf (this will only adjust disklabel to
the uSD card):

 # mount /dev/sd0a /mnt
 # vi /mnt/etc/rc.conf
 resize_disklabel_part=d
 resize_root=no

...while here we can also add:

 inetd=no
 ip6addrctl=yes
 ip6addrctl_policy=ipv4_prefer
 postfix=no

...and remove all services not needed (sshd, ntpd, creds_msdos, mdnsd,
devpubd).

OK, we're finally ready for the first boot!