chroot

You have installed a new fresh Freebsd to /dev/ad4 and want now to set it up while running the old system so you don’t have to much downtime.

Using chroot with the following commands:

mkdir /mnt/newfreebsd
mount /dev/ad4s1a /mnt/newfreebsd
mount /dev/ad4s1d /mnt/newfreebsd/var
mount /dev/ad4s1e /mnt/newfreebsd/usr

mount_devfs devfs /mnt/newfreebsd/dev
mount_procfs procfs /mnt/newfreebsd/proc

chroot /mnt/newfreebsd /bin/csh