On opening of Dataplicity remote terminal by default you're logged in as "Dataplicity" user on your remote device. This is an unprivileged service account. If you want to use sudo command from the Dataplicity terminal, for example to allow you to install programmes or manage your device, you must first switch to a more privileged user account and enter the password for that account.

On a Raspberry Pi, the default pi account is suitable. To switch to the pi user, generally indicated by the [email protected]:/ $ prompt, just type:

su pi

You will be asked to enter the pi account password which, unless you have changed it, is raspberry.

From there you can sudo as normal:

sudo cat /etc/shadow