Debian Linux: Set a Serial Console

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.

viaDebian Linux: Set a Serial Console.