[hllug] Setting up a serial console

  • From: Lee Parmeter <geek@xxxxxxxxxxxxxx>
  • To: hllug@xxxxxxxxxxxxx
  • Date: Mon, 03 Dec 2007 22:21:38 -0600

A serial port can be setup for use as a console quiet easily. This would be quite handy if the Ethernet port fails and you need to get into the machine to fix it! (Or the wireless card fails to find the network at the library! :<))

This example setups up COM1 (ttyS0) with the following settings: 38400 baud, 8 bits, 1 stop, no parity:

1. To enable the GRUB menu, add the following to /boot/grub/menu.lst:

serial --unit=0 --speed=38400 --word=8 --parity=no --stop=1
terminal --timeout=10 serial console

2. To redirect the messages during the boot process, append the following kernel parameters:
"console=tty0 console=ttyS0,38400n8". For example:

title CentOS (2.6.18-53.1.4.el5) (hd0)
root (hd0,0)
kernel /vmlinuz-2.6.18-53.1.4.el5 ro root=/dev/md2 rhgb quiet console=tty0 console=ttyS0,38400n8
initrd /initrd-2.6.18-53.1.4.el5.img

Note: enabling the redirection of the kernel messages will disable the usplash screen on the video monitor.

3. To enable serial console login once the system is booted, add "agetty" to "/etc/inittab". For example:

# Run gettys in standard runlevels
co:2345:respawn:/sbin/agetty ttyS0 38400 vt102

Now reboot the computer and connect a laplink style serial cable between this computer and another "client" computer. Start a serial terminal program like "minicom" (set to 38400 baud) on the client and you should see some text asking you to press any key or maybe the GRUB menu once the timeout (10 seconds) has expired. Once the system has full booted, you can login to the machine using your own account or the root account.


Lee Parmeter

"When it comes to Vista, just say NO! If your not ready for Linux yet, buy a MAC!" - Lee Parmeter

Highland Lakes Linux User Group (HLLUG): http://www.hllug.org
HLLUG mailing list: http://www.freelists.org/list/hllug

Other related posts:

  • » [hllug] Setting up a serial console