$ sudo systemctl status mssql-server
 ? mssql-server.service - Microsoft SQL Server Database Engine
    Loaded: loaded (/usr/lib/systemd/system/mssql-server.service; enabled; vendor preset: disabled)
    Active: active (running) since Wed 2018-06-06 16:55:41 CEST; 5min ago
      Docs: https://docs.microsoft.com/en-us/sql/linux
  Main PID: 3082 (sqlservr)
    CGroup: /system.slice/mssql-server.service
            ??3082 /opt/mssql/bin/sqlservr
            ??3103 /opt/mssql/bin/sqlservr