copying just / (not /tmp, /usr, etc) (rsync -x failed)

[lveax]

On Dec 5, 2007 12:38 AM, Steve Franks <stevefranks at ieee.org> wrote:
> I have / on one slice, and [usr,tmp,var] on others.  I want to move
> just / to a new disk, which seemed to be what rsync -x ("do not cross
> filesystems") was intended for.  It failed, however, as df shows 20k
> blocks in /, and rsync filled up the target slice with 50k blocks, so
> obviously it blew right past the 'end' of / - did I miss something? Is
> there no other way except to umount [tmp,usr,var]?
>
try:
 dd if=/dev/${the / slice} of=/dev/${the new / slice} bs=1m

or just go to single user mode umount /tmp /usr /var then copy it..