Console on serial port

Example using RedHat Linux 6.0

Using lilo bootloader

Edit /etc/lilo.conf

append="console=tty0 console=ttyS0,9600n8"

boot=/dev/hda
map=/boot/map
install=/boot/boot.b
prompt
default=linux
# Changes for serial console on COM1: in global section
#   Deleted: message=/boot/message
serial=0,9600n8
timeout=100
restricted
password=de7mGPe3i8

image=/boot/vmlinuz-2.4.2-2
  label=linux
  read-only
  root=/dev/hda6
  initrd=/boot/initrd-2.4.2-2.img
  # Changes for serial console on COM1: in each image section
  append="console=tty0 console=ttyS0,9600n8"

bash# lilo
Added linux *

Edit /etc/inittab

S0:12345:respawn:/sbin/mingetty ttyS0 9600 vt100

Adding the terminal to the secure list so that root can login

Needed in this particular case but avoid doing this because it is not a good practice regarding security

Edit /etc/securetty

ttyS0

Links:

https://tldp.org/HOWTO/Remote-Serial-Console-HOWTO/configure-kernel-lilo.html

https://www.kernel.org/doc/html/v4.15/admin-guide/serial-console.html