I've built a headless box that's going to live in Japan when I go back to Ireland. There'll be no one in Japan to fix it if it goes bad. The best I can do is get someone to insert a CD and reboot but after some searching and some asking it seems none of the bootable CDs will boot the machine into a useful state for remote admin. slax was recommended to me on TLUG as a good customisable distro. It turned out to be pretty easy thanks to slax's rootcopy feature which allows you to make minor modifications without digging around (too much) in the compressed package files. I've broken the process down into a few steps, with a quick bash script for each one.
Create a directory to work in and cd into it
mkdir slax cd slax
Get a copy of the .iso
You need slax-frodo-x.y.z.iso, you can get it from the slax download page. The frodo edition is the minimal version on which all the others are based.
Make a copy of the files from the CD
This is necessary because we need to add some files. So I ran this as ./prep_image.sh ~/slax-frodo-5.1.8.iso
It's disabled by default (rc.sshd is not executable), so I replace it with one that is executable. I also turn off password logins because everyone knows the root password for slax. Finally I include an authorized_keys file so that I can ssh in with my ssh key. I ran this script as ./enable_ssh.sh ~/.ssh/authorized_keys
Update a dyndns entry
The machine is on a cable modem and doesn't have a fixed IP, so I need to know where it is. I downloaded the ddclient module and the following script puts it in place, puts your ddclient.conf file into /etc and makes sure that it gets started on boot (I assumed it would start by itself actually, I'm not sure if that's a bug or not). I invoked this script as ./ddclient.sh ddclient.conf
Add any other modules
There doesn't appear to be an editor in the slax-frodo image so I grabbed joe and copied the .mo into slax/base/
Move files into place and create a new .iso
So far everything we've done has been in a rootcopy/ directory in the current directory. Now it's time to move that into place in slax/ and invoke the iso building script with the following script which outputs it to slax-ssh.iso in the current directory.
Test it in qemu
qemu -cdrom slax-ssh.iso should boot up. I never figured out how to get qemu bring up a real IP interface - the virtual machine can connect to the outside world but I can't connect to it. I tested it by setting up an ssh tunnel connecting port 22 on the VM to port 2022 on the host machine with ssh -R2022:localhost:22 firstname.lastname@example.org. Then I did ssh -p 2022 root@localhost with my ssh keys loaded and in I went. When my keys aren't loaded, I don't get a password prompt so I can't get in. Perfect.