ArchLinux: 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. ttyS0 will be managed by login prompt and tty1 will be managed by display manager like lxdm.
$ diff -uprN /etc/default/grub{.org,}
--- /etc/default/grub.org       2016-06-06 18:06:46.053333327 +0000
+++ /etc/default/grub   2016-06-06 20:28:12.563333332 +0000
@@ -1,7 +1,7 @@
 GRUB_DEFAULT=0
 GRUB_TIMEOUT=1
 GRUB_DISTRIBUTOR="Arch"
-GRUB_CMDLINE_LINUX_DEFAULT="quiet"
+GRUB_CMDLINE_LINUX_DEFAULT="console=tty1 console=ttyS0,115200"
 GRUB_CMDLINE_LINUX=""

 # Preload both GPT and MBR modules so that they are not missed
@@ -11,8 +11,11 @@ GRUB_PRELOAD_MODULES="part_gpt part_msdo
 #GRUB_HIDDEN_TIMEOUT=5
 #GRUB_HIDDEN_TIMEOUT_QUIET=true

+GRUB_TERMINAL="console serial"
+GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
+
 # Uncomment to use basic console
-GRUB_TERMINAL_INPUT=console
+#GRUB_TERMINAL_INPUT=console

 # Uncomment to disable graphical terminal
 #GRUB_TERMINAL_OUTPUT=console

2 grub-mkconfig

Update /boot/grub/grub.cfg with grub-mkconfig.

$ sudo grub-mkconfig -o /boot/grub/grub.cfg
Generating grub configuration file ...
Found linux image: /boot/vmlinuz-linux
Found initrd image: /boot/initramfs-linux.img
Found fallback initramfs image: /boot/initramfs-linux-fallback.img
done

Reboot ArchLinux.

$ sudo reboot

3 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

tty1 is managed by display manager.

If pressing Ctrl + Alt + F2, tty2 will be managed by login prompt.

0003_Linux-to-Display.png

Login prompt to serial console is as below.

0004_Linux-to-SerialConsole.png