Serial console for headless systems

[anatoly-savchenkov]

It would be great if ESP-KVM could support a serial console for the target system.

A good example is the Intel SS4200-E. It has no video output at all, so HDMI capture is not an option. Its intended local management interface is the serial console, which can be used to see boot messages, access BIOS, interact with the boot process, and log into the OS.

Combined with existing ESP-KVM features such as virtual CD/media and power control, this would enable fully remote recovery: mount an ISO, reboot, and perform the entire boot/recovery process through the serial console.

For systems like the SS4200-E, serial is effectively the only out-of-band console, so supporting it would make ESP-KVM useful for a wider range of headless servers, NAS appliances, routers, and embedded systems.

[dexif]

Thanks! I've wanted to add this for a while, just haven't got to it yet. A UART on the board's header and a terminal in the console should do it.

Which connector and speed does the SS4200-E use for its console? I don't have one.

[anatoly-savchenkov]

The SS4200-E uses a 2x5 RS-232 header, typically broken out to DB9, at 115200 8N1.

Signal levels are true RS-232, not 3.3V TTL, so an external level shifter such as a MAX3232 would be needed.

[dexif]

Settings -> Power -> Serial console, pick two free pins and 115200, then use the terminal button in the console. I tested it with a Raspberry Pi wired straight in. I don't have a MAX3232 at hand right now, so I couldn't try it with real RS-232 yet.

You can also use netconsole: turn it on in Settings -> Network, and the box's kernel log shows up in the console over the network.

https://espkvm.io/blog/0-60-0-a-serial-console-and-logs/