Encrypting full disk with several slices

[OxY]

Hi!

I would appreciate some help from you..i
 failed to find anything on google and manpages about this topic..

My goal is to encrypt my root partition with geli or gbde. First, I tried
geli, man page said that it's ok to encrypt root partition (just leave 
unencrypted
the /boot part, so i put it on other slice), but it's not so simple..

tried to encrypt the full disk first, then create the partitions and slices
to be able to use just one key/pass, it's not so convinient to type
9 passwords per boot..
i used the cmds:

# dd if=/dev/random of=/boot/ad2.key bs=64 count=1
# geli init -s 4096 -K /boot/ad2.key /dev/ad2

then partition the disk:
created fdisk config file (which works on unencrypted partition) (just with 
test length, i know is's small :)

p       1       165       1     8192


it said: length must be a multiple of sector size..
sector size is 4096, so dunno what's the matter..(tried with 16384, so 
on...)

Now, i am thinking about first create partitions and slices, (ad2s1a,d,e,f,g 
; ad2s2d,e,f,g)
then encrypt them one-by-one ..my only problem is to how can i manage it to 
ask for one password when
i boot....

Thank you and sorry for my poor english..