This is how i took an existing Solaris 9 sparc/Debian Linux machine
and had it help me install Solaris 10u10 on a new Sun Netra X1.
It already had nfsd/mountd running and tftpd working via inetd.

Note: Debian installs fail with: The disk you inserted is not a Solaris OS CD/DVD.

Assumptions:
10.0.0.20 is your netboot install server
10.0.0.21 is the ip address you want your new machine to use
0A000015 is each octet of 10.0.0.21 in hex
0:0:ba:f:1e:c1 is the ARP address of the new machine

# Set up your netboot install server:
echo "10.0.0.21 newmachine.example.net" >> /etc/hosts
echo "0:0:ba:f:1e:c1 10.0.0.21" >> /etc/ethers
if [ `uname` = Linux ] ; then
    apt-get install portmap bootparamd rarpd tftpd
    # nfs-kernel-server WILL NOT WORK as of 2012.07.05 debian 6.0.5
    # 3a000 boot failed
    # Enter filename [boot_archive]:
    # inetboot getattr ERROR: No such file or directory
    cp /etc/exports /etc/exports.t
    apt-get purge nfs-kernel-server
    wget -O /usr/local/src/unfs3-0.9.22.tgz 'http://downloads.sourceforge.net/project/unfs3/unfs3/0.9.22/unfs3-0.9.22.tar.gz?r=http%3A%2F%2Funfs3.sourceforge.net%2F&ts=1341477986&use_mirror=superb-sea2'
    cd /usr/local/src
    tar zxf unfs3-0.9.22.tgz
    cd unfs3*
    ./configure ; make ; make install
    mv /etc/exports.t /etc/exports
    echo "/sol10u10_sparc     10.0.0.0/24(ro,async,no_root_squash,anonuid=0,anongid=0)" >> /etc/exports
    echo "10.0.0.21 root=10.0.0.20:/sol10u10_sparc/Solaris_10/Tools/Boot \
           install=10.0.0.20:/sol10u10_sparc" \
           boottype=10.0.0.20:in \
           rootopts=10.0.0.20:rsize=8192" >> /etc/bootparams
elsif [ `uname` = SunOS ] ; then
    echo "share -F nfs -o ro,anon=0 /sol10u10_sparc" >> /etc/dfs/dfstab
    echo "* root=10.0.0.20:/sol10u10_sparc/Solaris_10/Tools/Boot \
           install=10.0.0.20:/sol10u10_sparc \
           rootopts=:rsize=8192" >> /etc/bootparams
fi

mkdir /sol10u10_sparc

if [ `uname` = Linux ] ; then
    modprobe loop
    mount /home/sol10-u10-ga-sparc-dvd.iso /sol10u10_sarc -t iso9660 -o loop
elsif [ `uname` = SunOS ] ; then
    lofiadm -a /home/sol-10-u10-ga-sparc-dvd.iso /dev/lofi/1
    mount -F hsfs -o ro /dev/lofi/1 /sol10u10_sparc
    shareall
fi

cp /sol10u10_sparc/Solaris_10/Tools/Boot/platform/sun4u/inetboot \
 /tftpboot/inetboot.sol10u10.sun4u
ln -s /tftpboot/inetboot.sol10u10.sun4u /tftpboot/0A000015
if [ `uname` = Linux ] ; then
    unfsd  
    /etc/init.d/rarpd restart
    /etc/init.d/bootparamd restart
elsif [ `uname` = SunOS ] ; then
    /usr/sbin/in.rarpd -a
    /usr/sbin/rpc.bootparamd
fi

# then, on the machine i'm trying to netboot:
# ok boot net - install

# this will start and you'll see
# Boot device: /pci@1f,0/ethernet@c File and args: - install
# 3a000 |

# for more verbosity during netboot, use: boot net -v - install