Drone signs authentication cookies using a secret key that is randomly generated when the server starts. Every time you restart the server a new key is generated, which means existing sessions are terminated. We can avoid terminating existing sessions on restart by providing the server with a static secret key.
Create a secret key:
$ openssl rand -hex 16 bea26a2221fd8090ea38720fc445eca6
Provide the server with the secret key:
$ docker run \ -e DRONE_COOKIE_SECRET=bea26a2221fd8090ea38720fc445eca6
Drone creates cookies with a default timeout of 30 days (720h). When the cookie expires the user sessions is terminated and the user will be required to login. You can customize the cookie timeout through the environment.