Since grml (https://grml.org/) provides the possibility to pass a command line parameter (ssh=<password>) to start the sshd inside the live system it’s the perfect base for creating an ssh-enabled-live-usb-system.
- Download your flavour (i586/amd64, the grml-small suites our needs) of grml (https://grml.org/)
- Install it on your usb stick (see http://wiki.grml.org/doku.php?id=usb)
- Edit boot/syslinux/grml32_small_default.cfg and append “hostname=sshd ssh=Start123” to the line starting with “append”
- Boot the machine with the stick after some amount of time you can connect using “ssh root@sshd” (you can decrease the 30 seconds timeout in the bootscreen by editing boot/syslinux/syslinux.cfg)
If you prefer ssh keys over passwords take a look at http://blog.grml.org/archives/367-Create-a-Grml-ISO-image-with-your-own-ssh-keys-for-password-less-login.html