Remote-Accessible Live-Distribution (aka Live CD)

Question

I'm looking for a live distribution (live CD or the likes) which comes - per default - with sshd running at startup.

I want to check the components of my laptop whose graphics has died (card-replacement did not do the trick).

The system seems to boot into Knoppix 6 just right (and in typing commands without a screen I can get it to shut down regularly) but what I need is a live distribution (CD/DVD/USB) which I can fire up and log into (via ssh) over the network to check whether the CPU & memory is OK and if the new graphics card is ok too.

What options exist?

Answer 1

I came across the same problem. I decided build my own live linux (USB based).
You can configure networking via syslinux.cfg on the usb stick.
It starts openSSH by default. It comes with nearly no functionality, appart from mounting a drive and chrooting the target system.

You can download it here if you still need it http://heyn-it.de/index.php/ssh-rescue-linux.html

Answer 2

I just tried Plop linux to boot a usb drive in an old desktop pc and when the ploplinux distro booted I noticed the sshd service.

After that I run the ifconfig to check the local ip and did a ssh connection from a remote laptop:

command:  ssh root@ipaddress 
password: ploplinux 

Answer 3

As a rule, live distributions don't come with sshd enabled, because if you can log in over sshd, so can anyone else. Your machine may be on a private network where you are the only user, but that's a rather special case. In general, to be useful, the live distribution needs to have a custom password or other authentication mechanism for every user.

You can start sshd blind, but typically that won't be enough: you'll also have to configure authentication for some account.

You should take a live distribution and customize it by making it start sshd automatically, and additionally creating a password-protected account or adding an entry to ~/.ssh/authorized_keys. Either make sure that PermitRootLogin is set to yes in /etc/sshd_config, or add a password for the root account, or make the account you can log in to a sudoer account (and give it a password).

For Knoppix, the easiest way to do this customization is to install it to a USB disk and activate its persistent memory feature (illustrated howto). Then edit the configuration files you want in /etc.

Answer 4

Debian installer (d-i) was faced with a similar problem and their solution might be found useful. Firstly a note on the architecture of d-i: d-i is modular so by adding components in the form of udebs you can add functionality. the udebs can be added during image generation or runtime the module you are interested in is network console. if you want to install modules automatically at runtime a preseed file will do that.

Now here is how the network console module works:

1. it gets the password to use from the local console twice (preseeding can set this beforehand or use a already hashed password.

2. it generates a entry int he password file

3. it generates a host key

4. it starts sshd.

5. it sets a hook to copy the generated host key to the installed system.

the known drawbacks to this approach are:

1. preseeding the password is not very secure.

2. rerunning the installer will generate a different host key.

the password problem can be mitigated by installing an authorized keys list instead of a password (and using a invalid password hash.

The relevant parts of my preseed file are:

d-i anna/choose_modules string network-console,openssh-client-udeb
#d-i anna/choose_modules seen false
d-i network-console/password password r00tme
d-i network-console/password-again password r00tme
d-i preseed/early_command string mkdir .ssh; cd .ssh; wget http://192.168.0.1/debian/authorized_keys