Netbooting and NFS root for NetBSD on sparc64

So, you got a sparc64 machine (e.g. a Sun Fire V100) that you want to run NetBSD on. For ... reasons you want/need to netboot it and run it with a NFS rootfs. And your hosting environment for all that is mostly Linux. Well, let me describe what you need.

This is written for Linux hosts running Debian or Ubuntu.

requirements

• rarpd: apt install rarpd
• tftpd: apt install tftp-hpa tftpd-hpa
• dhcpd: apt install isc-dhcp-server
• NFS server: apt install nfs-kernel-server

assumptions

• MAC address of our sparc64 machine: 02:25:45:67:89:01
• hostname of our sparc64 machine: sparc64box
• IP address of our sparc64 machine: 192.168.1.1
• all necessary services hosted on a single Linux machine running Debian or Ubuntu

basic sparc64 NetBSD boot process

• At the firmware ok prompt trigger a netboot with: boot net
• The firmware netboot routine uses RARP (Reverse ARP) to ask "Hey, this is MAC address, what is my IP address?" With the answer from that, it sets its IP address and we can do local networking.
• Next, the firmware tries to load a netboot loader via TFTP from the RARP server.
• Control is transferred to this netboot loader which continues the process. We'll assume NetBSD here.
• A DHCP request is issued to get network config and boot config
• Using the provided boot host and NFS path, /netbsd is loaded and control transferred to it
• Once the kernel has come up, it issues a DHCP request again and then
  • Configures the network with that information.
  • Mounts, via NFS, the root file system based on the information in the DHCP answer.
  • Starts /sbin/init, which completes the boot process

Putting it all together

RARP

First, install the rarp service via: apt install rarpd. Then edit /etc/ethers with the following content:

02:25:45:67:89:01 sparc64box

TFTP

• Install the tftp server (and client, for testing): apt install tftp-hpa tftpd-hpa.
• Grab reasonably current NetBSD install image for sparc64 and extract the file sparc64/installation/misc/ofwboot from it, place it into the TFTP directory (typically /srv/tftp).
• The firmware tries to load (via TFTP) the netboot loader via a filename that is the encoded IP address handed out via RARP. We can arrive at this filename via:

        printf "%.2X%.2X%.2X%.2X\n"  192 168 1 1
        which gives us: C0A80101
      

• symlink a file of the above generated name to the ofwboot file

DHCP

• set up a standard DHCP entry for the host, with all the usual settings (identify host by ethernet address, set router, hostname, ...)
• To this host entry add the entries we need:
  • TFTP server name: option server-name "tftp-server-name"; and next-server tftp-server-name;
  • netboot loader file name: option filename "ofwboot";
  • NFS root path: option root-path "/nfsroots/sparcbox";
• restart the DHCP server

NFS server

• First, set up the root directory under /nfsroots/sparcbox - this can be done by either copying an existing installation from disk (and adjusting /etc/fstab along the way) or just unpacking the install image, which enables net install
• The NetBSD netboot loader only speaks NFSv2, so we need to enable support for that:
  • Older Debian: in /etc/default/nfs-kernel-server add the line RPCNFSDOPTS="--nfs-version 2,3,4".
  • In Debian starting with bookworm (and Ubuntu), edit /etc/nfs.conf in the [nfsd] group and add the lines:

                 udp=y
                 tcp=y
                 vers2=y
                 vers3=y
                

• Add an entry to /etc/exports for this: /nfsroots/sparcbox 192.168.1.1/32(rw,sync,subtree_check,no_root_squash)
• Restart the NFS service.

Boot