After unslinging your Slug, you should install openssh. This will allow you to connect securely (as opposed to using an unencrypted Telnet connection), and you won’t need to re-enable Telnet access every time your Slug reboots.

Installation is very simple:

ipkg install openssh

This will also install and configure openssl, and generate the necessary key and certificate files to enable encrypted connections.

If you don’t already have an SSH client you can download PuTTY for free from http://www.chiark.greenend.org.uk/~sgtatham/putty/.

Once you have successfully connected using PuTTY and SSH, you can turn off Telnet access to your Slug.

If this information was useful, please leave a comment to let me know!