FirstServed Tech Blog - FirstServed and the Art of Server Tuning

Hi,

If you want to configure a serial console on your Dell PowerEdge R410 (or R710) dedicated server with CentOS 5.4 (or 5.3 and probably also the Red Hat Enterprise systems) you can use these guidelines.
In the Bios:

Under "Serial Communication":
Serial Communication: On with Console Redirection via COM1
Serial Port Address: Serial Device1=COM2,Serial Device2=COM1
External Serial Connector: Serial Device2
Failsafe Baud Rate: 115200
Remote Terminal Type: VT100/VT220
Redirection After Boot: Enabled (so grub displays)

Then you configure Grub:

title CentOS (2.6.18-164.6.1.el5) Serial
root (hd0,0)
kernel /vmlinuz-2.6.18-164.6.1.el5 ro root=LABEL=/ console=tty0 console=ttyS0,115200n8
initrd /initrd-2.6.18-164.6.1.el5.img

This makes the kernel display it’s messages on screen and over the serial console.

In /etc/securetty append:

ttyS0
ttyS1

This way root can log in using the serial console.

Finally configure the inittab (/etc/inittab) and add the following line:

co:2345:respawn:/sbin/agetty ttyS0 115200 linux

Now reboot and enjoy pure serial console goodness over ip (ipmi).

(Oh, don’t forget to enable IPMI over lan in the iDrac configuration and to set a username, password and ip-address.
The iDrac 6 configuration flashes by when the server boots.)

Use this command to read the BIOS dmi data in linux:
dmidecode

Reads mainboard type, bios version, memory banks, …

Anyone who has ever played around with serial console operation, be it over a serial cable or with an IPMI-like serial redirection over LAN, has known the joys of trying to find working alternatives to the function keys.  Since one of the things you’ll be likely to do with a serial console is to enter the BIOS setup, and entering the bios setup usually requires the use of F1, F2 or F10, this is a bit of a poser.

Luckily for us, Dell in it’s neverending wisdom has seen fit to display all necessary escape sequences for its Serial BIOS at boot time.  The only hitch is that this screen flashes by so quickly that it’s impossible to read unless you’ve been gifted with x-ray eyes.  Armed with the Print-Screen key and Photoshop, we did some twenty reboots of the server and were able to decipher the following shortcuts:

Dell Serial Bios keyboard shortcuts

Note: Use your keypad for the <ESC>n sequences!