May 16, 2025

Sun 3/280 - running a raspberry pi as a remote console aceess point

The idea is that I want to put this noisy sun 3/280 into another room. I don't want to run a long serial cable to it. I have network in that room, and I have a Raspberry pi that I am not using. So I would like to set it up so I can ssh to the Raspberry pi, then run picocom on it to a usb to serial gadget connected to the sun 3/280.

Install dhcpd

Somehow I have lost this, probably during a fresh Fedora install a year ago. Surprisingly I have not needed or missed it until now.

Fedora has generated no end of confusion by having two packages named dhcpd and dhcp-server. I do this: 

su
dnf -y install dhcpd
This puts the files I expect into /etc/dhcp. Then I try to dnf remote this and install dhcpd-server instead. It doesn't understand removing dhcpd and' then tells me dhcpd-server is already installed! Who knows what this is all about, but I press on.

Somewhere I hope to find an old dhcpd.conf file on my system. I find a candidate in /oldroot/etc/dhcp, so: 

cd /etc/dhcp
mv dhcpd.conf dhcpd.Fedora
cp /oldroot/etc/dhcp/dhcpd.conf dhcpd.Tom
cp dhcpd.Tom dhcpd.conf

Start the server

systemctl enable dhcpd
systemctl enable dhcpd-service
systemctl start dhcpd (fails)
systemctl start dhcpd-service
Don't blame me for the confusion Fedora has generated with two names for the same thing.

Firewall rules

This seems easy: 
firewall-cmd --add-service=dhcp
firewall-cmd --runtime-to-permanent
It reports success for both of these commands, so I guess this worked.

Figure out the MAC address of my Rpi

I could hook up a serial console. What I will try instead is running wireshark and looking for action on UDP port 67 
su
dnf -y install wireshark
wireshark
I have only ever had luck running wireshark as root. I specify for a capture filter: 
udp port 67
This works! One thing I hate about wireshark is that whatever GUI package they used to build it does not support cut and paste. The MAC address is b8:27:eb:f0:04:1c. I add this entry: 
			host rpi {
                    hardware ethernet b8:27:eb:f0:04:1c;
                    fixed-address 192.168.0.29;
                    option host-name "rpi";
            }
Then I restart the server: 
systemctl restart dhcpd

Try it

I already have an entry for 29 in /etc/hosts.

I cycle power, see appropriate traffic via wireshark, then "ping rpi" and it works! 

ssh tom@rpi
This also works using the password I have noted down.

And I am extremely pleased to find that picocom is already installed on the rpi.

I plug in my USB to serial gadget and see /dev/ttyUSB0 appear, then: 

picocom /dev/ttyUSB0
.....
EEPROM: Using RS232 A port.
Selftest Completed.

Sun Workstation, Model Sun-3/200 Series.
ROM Rev 3.0, 16MB memory installed, Serial #13355.
Ethernet address 8:0:20:0:4:B1, Host ID 1300342B.


Testing 8 Megabytes of Memory ... Completed.

Auto-boot in progress...

EEPROM boot device...Boot: ie(0,0,0)
ie: No Carrier
All this took only a little bit over an hour.
Feedback? Questions? Drop me a line!

Tom's Computer Info / tom@mmto.org