AlpineLinux 3.8: extlinux and Linux with serial console

• Enable serial console and disable hidden menu in extlinux.
• Append console=ttyS0,115200 to kernel parameter. Delete quiet from kernel parameter. Kernel log and syslog will be output to serial console.
• Enable getty entry of ttyS0 in /etc/inittab.
• Enable login from serial console.

#!/bin/sh -e


. /etc/update-extlinux.conf
O="${default_kernel_opts} console=ttyS0,115200"
sudo sed -i /etc/update-extlinux.conf \
    -e 's/^serial_port=/serial_port=0/g' \
    -e "s/^hidden=1/hidden=0/g" \
    -e "s;^default_kernel_opts=.*;default_kernel_opts=\"${O}\";g" \
    -e 's;^default_kernel_opts=\(.*\)quiet\(.*\);default_kernel_opts=\1\2;g'
sudo sed -i /etc/inittab \
     -e 's;^#ttyS0;ttyS0;g'
sudo update-extlinux
sudo reboot

extlinux to monitor display is as below.

extlinux to serial console is as below. This article used "sudo virsh console <vmname>" for connecting serial console.

Login prompt to monitor display is as below. tty1 is displayed with press Ctrl + Alt + F1.

Login prompt to serial console is as below.