Small bootable package to enable ssh client?

Question

I've been trying to find the smallest possible package to put on a cd/thumbdrive that will allow me to use an ssh client on a wired networked computer. I'm talking about really barebones stuff, no fancy shells or wasted kernel modules, just an SSH CLI.

Since apparently no-one has bothered to make a bootable SSH client (according to every permutation of the words I could think to google), the best I've been able to come up with is my own remaster of TinyCore with gcc-libs, openssl, and openssh packaged into the initrd. Arguably that could be marginally smaller using TinyCore's tcz packages, but that's just extra work on boot. I'm looking for small in both size and boot time. The ISO winds up just over 11MB.

I've poked around the filesystem looking for things to nix, but I'm not sure I see anything obvious. I could remove drivers, kernel modules, or even kernel code, libraries and utilities, but I don't know enough to know what can go and what's necessary to get ssh up and running. Some simple modifications to openssh would make it usable as the default user shell, eliminating the need for a separate shell, and (hopefully) busybox.

So I guess my question unravels into two:
On top of the kernel, what's necessary to get into an SSH client?
Do you know of a smaller, faster way to get into an SSH client than my TinyCore remaster?

Answer 1

I think that a very stripped down version of busybox (just a basic shell and a few network configuration tools you may need for setting up the network) with the addition of dropbear as ssh client (statically linked) will be way under the 11mb you mention. I'd say around 1-2mb would suffice for sure, but you could trim it down even more. Plus add a minimal kernel near.

It depends a bit on your arch and so on of course (ie. dropbear statically linked for a MIPS system I have here is around 200kb, a basic busybox may fit in 500kb or so easily).