In the handbook Section14.5 Updating Multiple Jails has the following error/ommissions:

Section 14.5.1 under 3. Create a skeleton for the read-write portion of the system:

need to add the following: mv dev /home/j/skel

Section 14.5.1 under 4. Use mergemaster to install missing configuration files....

this:       rm -R bin boot lib libexec mnt proc rescue sbin sys usr dev
should be:  rm -R bin boot lib libexec mnt proc rescue sbin sys usr

Section 14.5.1 under 5. Now, symlink the read-write file system to the read-only file system....

# mkdir s                   should be # mkdir s s/portbuild
ln -s s/usr-local usr/local should be # ln -s ../s/usr-local usr/local
ln -s s/usr-X11R6 usr/X11R6 should be # ln -s ../s/usr-X11R6 usr/X11R6
ln -s s/distfiles usr/ports/distfiles should be 
ln -s ../../s/distfiles usr/ports/distfiles
and add ln -s s/dev/dev