Fedora 30: GRUB2 and Linux with serial console

This article will describe changing GRUB2 and Linux to serial console. This is not for desktop environment but embedded system and virtual machine environment.

1 /etc/default/grub

Change /etc/default/grub as below.

  • Change GRUB terminal to console and ttyS0. This will provide one GRUB to a monitor display and serial console.
  • Change linux kernel console to tty1 and ttyS0. This setting will be taken over to userland, and there will be two login prompt for tty1 and ttyS0.
#!/bin/sh -e

# shellcheck disable=SC1091
. /etc/default/grub
sudo cp /etc/default/grub /etc/default/grub.orig
cat <<EOF | sudo tee /etc/default/grub
GRUB_TIMEOUT=1
GRUB_DISTRIBUTOR="\$(sed 's, release .*$,,g' /etc/system-release)"
GRUB_DEFAULT=saved
GRUB_DISABLE_SUBMENU=true
GRUB_TERMINAL="console serial"
GRUB_CMDLINE_LINUX=\
"$(echo "${GRUB_CMDLINE_LINUX}" | sed -e 's; rhgb quiet;;g')"
GRUB_CMDLINE_LINUX_DEFAULT="console=tty1 console=ttyS0,115200"
GRUB_SERIAL_COMMAND=\
"serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
GRUB_DISABLE_RECOVERY="true"
GRUB_ENABLE_BLSCFG=true
EOF
sudo grub2-mkconfig -o /boot/grub2/grub.cfg
sudo reboot

2 Execution result

GRUB to monitor display is as below.

0001_GRUB-to-Display.png

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

0002_GRUB-to-SerialConsole.png

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

0003_Linux-to-Display.png

Login prompt to serial console is as below.

0004_Linux-to-SerialConsole.png