Enabling Intel AMT Serial over Lan (SOL) on Ubuntu

Grepping syslog for tty's, this was the only one to come up on my machine

$ sudo zgrep -a tty /var/log/syslog.*
...
Jun 26 08:25:53 taro kernel: [    1.786819] 0000:00:16.3: ttyS4 at I/O 0x30a0 (irq = 19, base_baud = 115200) is a 16550A
...

Finding the device from udevadm

$ udevadm info -a /dev/ttyS4
...
    ATTRS{device}=="0xa363"
...

Udev persisent rules, to ensure this device will always be /dev/ttySOL

# /etc/udev/rules.d/z25_persistent-serial.rules
KERNEL!="ttyS[0-9]", GOTO="no_serial"

ATTRS{vendor}!="0x8086", GOTO="vendor_not_intel"

# From udevadm
ATTRS{device}=="0xa363", SYMLINK+="ttySOL", ENV{COMMENT}="Serial-Over-Lan $attr{vendor}:$attr{device}"

GOTO="vendor_not_intel"

LABEL="no_serial"

Make udev do it's thing without a reboot

sudo udevadm control --reload
sudo udevadm trigger

Shoud now have a symlink to our tty

$  ls -lah /dev/ttySOL
lrwxrwxrwx 1 root root 5 Jul  1 20:58 /dev/ttySOL -> ttyS4

I didn't do any GRUB stuff but probably should, but for testing, starting getty on my new tty a login showed up in Serial over Lan

systemctl start getty@ttySOL.service