tcp2com and Emergency Management Service (EMS)


It's important to get access to machines even when they are defective, especially when your machines are hosted in a datacenter. This avoids you some travelling just because something was misplugged or misconfigured

And sometimes the ethernet access can fail (wrong firewall rule, ethernet card burnt...). The idea to secure your access to the machines is to use 2 null-modem cables for linking 2 machines A and B together. A has serial access to B, and B can access A.

Serial access becomes interesting once operating systems have introduced it into booting procedure.
On Linux, the system is available through serial by setting up tty correctly. Grub, one of the most used kernel loaders, implemented a serial access to make Linux booting visible from the beginning.
Microsoft introduced the serial support as a new feature with Windows 2003 Server. It gives the ability to control the machine via serial access. They call it out-of-band management and gave this service the name of EMS (Emergency Management Services).

Further reading is available on Microsoft website

How to configure it

To set it up simply run this command: bootcfg /ems on /port com2 /baud 115200 /id 0
This will change your systems boot.ini file with the correct entries to enable EMS, something like this:

[boot loader]

[operating systems]
multi(0)disk(0)rdisk(0)partition(1)\WINDOWS="Windows Server 2003, Standard" /fastdetect /redirect

The next step is to configure TCP2COM with this command: tcp2com --install tcp/7000 com1

Your done, you can now test with this command: telnet localhost 7000