you can use sysutils/mklivecd from pkgsrc to build a livecd. It is very easy.
Another way to build a custom livecd can be found here:
http://wiki.netbsd.se/index.php/How_to_build_your_own_NetBSD_LiveCD


2007/3/23, Jan Danielsson <jan.m.danielsson@gmail.com>:
> Hello all,
>
>   I'd like to create a maintenance boot CD from my NetBSD system. To
> answer the obvious question "Why not use the installation CD?": Because,
> as far as I can gather, there's no cgd support in it -- which I require.
>
>   I found this page: http://www.reedmedia.net/misc/netbsd/live-cd.html
>
>   ... which looks like a good place to start, apart from: "The
> following notes are out-of-date. THIS IS OUT-OF-DATE." :-)
>
>   Want I want is to be able to boot from a CD, and have some basic
> commands. The most advanced application I need is "vi".
>
>   I want to restructure my partition layout due to a newly installed
> hard drive. I will need to mount my new disk (cgd:d), mount my "old"
> disk (some slices are cgd:d), copy all of the "old" stuff to the new
> disk. Repartition the "old" disk, and then copy everything back on to
> the "old" disk with the new layout. install_boot on the "old" disk. Reboot.
>
>   Surely someone must have created such a CD before, and have a rough
> idea about what I need to do? I'm not at all interested in getting X
> running. I only need the command line tools.
>
>   Oh, and I would also like to know how to best preserve all relevant
> data when I copy (or tar) the files from the old disk to the new one,
> and then copy (or untar) it back later.
>
> --
> Kind regards,
> Jan Danielsson
>
>
>
>