Talking to a headless Gentoo box

Havin_it · Posted: Fri Feb 19, 2010 5:29 pm Post subject: Talking to a headless Gentoo box

Hi all =)

For a while now I've had a home server running Gentoo, and for those times when I needed to access it directly (e.g. while building the system and then whenever boot failed), I'd use a device called an AverKey. This is a USB-powered VGA-to-component video adapter, which I'd use to get the server's display up on my (old, analogue) television. I'd also plug in a keyboard when using this.

However, I've just moved house and it's no longer feasible to have the server within cable-reach of the TV. What I'd like to know is, is there any way I can view and control the server (from Linux kernel boot onwards, let's assume it still POSTs okay) using another Gentoo box?

I never thought of this before, but I was reading recently about the SheevaPlug computer and how this can be administered via a USB cable from a terminal emulator. I have two laptops, both with USB and one of which also has a serial port if that's any help. Can I use these?

FWIW, the server is a Dell Poweredge 2400. It has PXE and Wake-On-LAN capabilities, though I don't know if either of these are likely to be relevant here. Happy to hear any theories, however long-shot, on how this might work.

Hypnos · Posted: Fri Feb 19, 2010 5:59 pm Post subject:

The problem is that x86 machines can't configure a serial terminal at the BIOS level, only at the kernel/init level as described here. One solution to this problem is to use PC Weasel, which emulates a VGA device and PS/2 keyboard and connects to a serial port -- all you need is a null-modem cable.

If you don't care about using a serial terminal per se, just want some way to talk to the machine, a KVM2USB may be the best solution. It shows the headless machine as a VNC.
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DaggyStyle · Watchman Joined: 22 Mar 2006 Posts: 5910

if you have a network/internet connection, then you can use ssh
here http://www.revsys.com/writings/quicktips/ssh-tunnel.html
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boerKrelis · Posted: Fri Feb 19, 2010 10:25 pm Post subject:

Grub will happily output to serial, too. Serial seems the way to go since you are willing to assume it'll POST.

Havin_it · Posted: Mon Feb 22, 2010 11:34 am Post subject:

Thanks all for the replies, and sorry for the delayed reply (living out of boxes, no reliable net access yet!)

SSH is what I use now for most admin, but every so often something goes spectacularly wrong with an update and I need to get a screen attached to find out why the kernel or an init process has crapped out, and SSH isn't early enough for that (in fact, these type of problems usually mean sshd never starts).

I must admit I didn't realise there'd be a necessity for extra hardware in order to use a serial terminal. If it comes to that, perhaps I'm better investing in a cheapo old monitor (or ~15m of component and keyboard cable

) so I can also see the BIOS if desired.

Dr.Willy · Guru Joined: 15 Jul 2007 Posts: 547 Location: NRW, Germany

http://ubuntuforums.org/showthread.php?t=855849

Havin_it · Posted: Mon Feb 22, 2010 2:11 pm Post subject:

Havin_it · Posted: Mon Feb 22, 2010 2:31 pm Post subject:

Just found this, which seems to suggest it can be done with just a serial (null-modem) cable between two Linux computers. Am I reading it right?

John R. Graham · Posted: Mon Feb 22, 2010 2:34 pm Post subject:

Yep. Grub will do serial and so will the kernel. You can use something like net-dialup/minicom as your serial terminal.

- John
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Havin_it · Posted: Tue Feb 23, 2010 9:12 am Post subject:

Excellent news! Now I just need to get hold of a cable, and work my way through that sizeable document.

One more question, if anyone knows: once I add the extra directives to grub.conf, will boot still succeed if the other computer isn't connected? Or will I need to create a separate boot entry?

John R. Graham · Posted: Tue Feb 23, 2010 1:24 pm Post subject:

Grub can be made to succeed with a default menu selection and a timeout regardless of whether it's displaying its menu on a serial console or a PC screen.

- John
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Dr.Willy · Guru Joined: 15 Jul 2007 Posts: 547 Location: NRW, Germany

Havin_it · Posted: Wed Feb 24, 2010 3:53 pm Post subject:

Sorry Dr. Willy, I see what you mean now :oops:

I'd rather get the serial console working in this instance, but that is definitely a good tip for the future. It's exactly what I was looking for when I did the initial install on this machine, and never actually found a solution at the time.

richard.scott · Posted: Mon Mar 01, 2010 2:37 pm Post subject:

how far are you from your serial port on the server?

Perhaps you could get a bluetooth serial adapter.... plug this into your servers serial port and then connect to it via bluetooth on your laptop.

http://www.usbnow.co.uk/Bluetooth_Devices/c31/p783/Mini_Bluetooth_Serial_Adapter_-_100m/product_info.html

You may be able to find something similar on a local website too.

Rich.