Possibilities of connecting to linux box console without network

Having to manage a couple of remote dedicated servers, working with network related stuff can be quite stressful.

Is there any possible way I could connect to those boxes (possibly via third box) and not have to depend on their networking configuration at all?

Something like "xm console", but not xen related? Hope my question is clear enough to answer.

Solution 1:

If your server has a serial port you can connect through it easily enough. Let us assume the simplest case; 1 server and a cart pc or laptop. Add an entry to your /etc/inittab file similar to:

s0:12345:respawn:/sbin/agetty 19200 ttyS0 vt100

That will tell the server to listen on ttyS0, the first serial port, for terminal like behavior. Plug a cable from that port on the server to your laptop/cart. Using a program such as minicom or the right options on screen connect to your local serial port. Assuming you properly configured the speeds you should drop straight into a login prompt on your server.

For the more complicated case, many different servers, you can centralize the same basic approach. Instead of a mobile cart or laptop, setup a specialized server that will be directly connected to all of your various devices. This can be done with a boatload of serial ports, or something like a Digi console server. From this console server you can then gain out-of-band access to any of your connected systems. I would check out applications like Conserver when working in bulk.

I would recommend, at least, configuring the serial port on these systems even if you don't plan on using an enterprise wide management system. You can't always trust that a box will have video, and at least with the serial port enabled you can work on a system that may not completely boot.

EDIT: After sleeping on it I realized this method will not work for virtual machines. Best case, using a serial connection you could drop into a shell on the VM host, but not any of the guests. We leave this problem as an exercise for the reader.

Solution 2:

Many server hardware vendors offer some kind of remote console, like IBM's RSA (System x) or Dell's DRAC (PowerEdge) and HP's iLO. This will still be over the network, and a good practice is to put that on a management VLAN that you otherwise don't mess with.

Newer server models might not actually have a serial port available to connect a serial console to (remote or otherwise), but there are USB adapters available.

And this is why data center hosting facilities have "hands and eyes" support :-).