How can I see logs in a server after a kernel panic hang?

To log a kernel panic, using netconsole is way easier than using a serial link ;)

There is a useful entry about it on ubuntu wiki that can be used on other linux flavors... Helped me for instance with archlinux.

Note that netconsole can be also be setup at boot.

Generally in these situations I've set up a remote serial console and then made sure to log everything that appears on the console. You can do this by connecting the serial port of the machine to another machine via an rs-232 cable. This might be getting a little tricker these days as serial ports are gradually disappearing, but I think most servers still have them.

Then on that other machine, run conserver and configure console logging. This provides a good way to both log everything on the console and provide an alternate login path to the system.

If you don't want to set up and adminster another linux box, an alternative is to install a serial console server. Various companies such as Avocent, Cyclades, and Raritan make these boxes which provide a network interface to 2-48 serial ports. However this sort of thing will be more expensive than just setting up another linux box of course.