Debian Linux: Set a Serial Console
by Vivek Gite on January 22, 2011 · 2 comments
How do I set up a serial console on Debian Linux HP server for troubleshooting and login purpose?
To setup a serial console you need to edit the following files under Debian Linux:
/boot/grub/menu.lst or /etc/default/grub (recommended for grub2)
/etc/inittab
/etc/securetty
Our Setup
You can list your working serial port under Linux as follows:
# setserial -g /dev/ttyS[0123]
Sample outputs:
/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3
/dev/ttyS0 (COM1) is detected and working serial console under Linux. For testing purpose, I’m going to set baud rate to 19200 and terminal type to vt100.
Grub Configuration (Grub2)
Edit /etc/default/grub, enter:
# vi /etc/default/grub
Append / modify as follows:
GRUB_CMDLINE_LINUX=’console=tty0 console=ttyS0,19200n8′
GRUB_TERMINAL=serial
GRUB_SERIAL_COMMAND= »serial –speed=19200 –unit=0 –word=8 –parity=no –stop=1″
Save and close the file. Next run the following command to generate a grub2 config file /boot/grub/grub.cfg :
# update-grub
A Note About Grub Legacy (older version)
If you are not using GRUB2 update /boot/grub/menu.lst (grub legacy) with kernel line as follows with console port, and baud rate:
title Debian GNU/Linux, kernel 2.6.32-5-486
root (hd0,0)
kernel /boot/vmlinuz-2.6.32-5-486 root=UUID=b598f856-2a2a-46d5-b60a-95826cfc7bf6 ro console=ttyS0,19200 earlyprint=serial,ttyS0,19200
initrd /boot/initrd.img-2.6.32-5-486
Save and close the file.
/etc/inittab Configuration
Edit /etc/inittab, enter:
# vi /etc/inittab
You need put a getty on a serial line for a terminal:
T0:23:respawn:/sbin/getty -L ttyS0 19200 vt100
Save and close the file.
/etc/securetty Configuration
Edit /etc/securetty, enter:
# vi /etc/securetty
Make sure UART serial ports /dev/ttyS0 is listed:
ttyS0
Save and close the file. Now, you can reboot the server for testing purpose.