Depending on the desktop version of your OS (macOS, linux or Windows), you can use any number of apps to get SSH connection with your NAS (Terminal, shellngn, putty, etc).Such a novice.... while am in as admin on Synology, the command prompt shows my user name and sudo or su are not engaging. The username yesterday when things were working was ash-4.4#
root can then be executed using your default DSM account. Once logged in, simply elevate with
sudo -i and repeat your DSM user password. This should give you
root@xxx$ command prompt that you can then use for any
docker container or
docker run commands.