What is serial console support?

Serial console will allow you to send all text based output to one of the onboard serial ports. When combined with a remote console device like a terminal server, will allow you to remotely administrate the machine even if the network has failed or crashed.

Enabling console redirection in the BIOS

Console redirection in the BIOS allows you to access all setup features, and any diagnostic information that is normally printed to the screen when your system boots. Most nodes from Advanced Clustering enable serial console support, but not all do. If you have questions please contact support.

1. When the machine is first turned on press the F2 key or the DEL key (depends on your system) to enter the BIOS
2. Look for the "Console Redirection" menu option, this is normally under Advanced Features, or Remote Access
3. Use the following settings
   1. 1st serial port (many times labeled COM1)
      
   2. Set the baud rate to 115200
   3. Turn off any flow control
      
   4. Make sure the emulation type is set to VT100
      
   5. The option "Continue after POST" should be disabled

Enable serial redirection in the GRUB boot loader

• Edit the file /boot/grub/menu.lst
  
• Disable any splashimage options, graphics can't be displayed across the serial port
  
• Add the following lines at the top of the file

serial --unit=0 --speed=115200
terminal --timeout=10 console serial

• The first line tells GRUB to use the first serial port at a baud rate of 115200
  
• The second line gives the user 10 seconds to decide where GRUB should output it's information. When loaded you will have 10 seconds to press any key via either the serial console device, or from a directly attached keyboard. If no key is hit the output will be the first item listed, which in the above example is the physically attached console (monitor and keyboard)

Enabling serial output from the Linux kernel

To enable serial output from the Linux kernel an argument must be given, this too is done via the /boot/grub/menu.lst file. On the "kernel" lines in the file append the following arguments:

console=tty0 console=ttyS0,115200

When multiple console= options are listed like above, the Linux kernel will output to both when possible. Once the kernel has loaded the device /dev/console will be linked to the last console= device listed.

Logging in via the serial console

The last step to setting up the serial console setup is to allow logins via the serial device. This can be done by running a getty process on the serial port device. To enable this you will need to edit /etc/inittab and add a line like below. Many times a very similar line has already been entered in the inittab file but just commented out.

S0:12345:respawn:/sbin/agetty -L 115200 ttyS0 vt100