Before we begin please note: Remote Access is generally only intended for situations in which a regular login is no longer possible due to a faulty configuration. Otherwise, access should always be made via SSH or similar services of your colocation computer.
If you book the Remote Access option, you get access to the serial console of your colocation computer via SSH. So you can reach it even if the network access is not possible anymore, e.g. due to a failed firewall rule:
The connection between our SSH service and your Linux kernel is established by using a serial adapter provided by us (see Can I use all GPIO pins of my Raspberry Pi? for a little more technical details). The following environment is currently supported and required by us:
Raspberry Pi 3 or 4 with Linux operating system and uart activation.
We recommend the installation of Raspberry Pi OS where uart can be enabled in /boot/config.txt. Users of the nano editor also need an additional configuration adjustment to prevent connection errors. Please see this wiki page for all setup instructions. More background knowledge can be found in this Adafruit article.
Please note: The option can always be booked, but officially we only recommend it for the Raspberry Pi 3 and 4, which we have tested extensively. If you have successfully validated that your device and your software also support the feature, then there is nothing to stop you from booking it. In this case, please send us a meaningful photo with description showing how to connect the serial adapter to the pins of your device.
Please also see What happens if I can’t access my devices anymore? for more details about remote maintenance. And have a look at Why does my Remote Access seem to stop working? if your Remote Access connection fails.