1.Connecting Remotely to SQL Server on Linux
Checking the ports running.
-To enable these connections remotely you will need to open the Linux firewall to accept traffic on those ports
-This action will depend on the type of firewall you are running on Linux. If you are not running any firewall, then you don't need to do anything since all traffic will be allowed by default.
#### FIREWALLS ON UBUNTU
There are two widely used firewalls that run on Ubuntu.
1.Uncomplicated Firewall (UFW)
2. firewalld which is a separate package that requires installation. These two firewall packages run on different distros.
Let's find out if any of them are running:
NB/:if firewalld is not found check this documentation.[here] to install it.
NB:User Datagram Protocol (UDP) – a communications protocol that facilitates the exchange of messages between computing devices in a network. It's an alternative to the transmission control protocol (TCP). In a network that uses the Internet Protocol (IP), it is sometimes referred to as UDP/IP.
NB:The Transmission Control Protocol is one of the main protocols of the Internet protocol suite. It originated in the initial network implementation in which it complemented the Internet Protocol. Therefore, the entire suite is commonly referred to as TCP/IP.
Enable SQL Server Dedicated Administrator Connection(DAC)
2.Using DAC with SQLCMD
You need to be a member of the sysadmin fixed server role in order to use this feature. The "-A" switch is used to specify that the user is trying to connect to SQL Server using the Dedicated Administrator Connection.
The syntax to use DAC is mentioned below.
SQLCMD -S [SQL Server Name] -U [User Name] -P [Password] -A
NB: FOR MORE CHECK ON THE LINK ABOVE!
NB:ALSO check this link.its interesting