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Version: 1.0

Firewall and Security Group

About Firewall

In Linux, the firewall exists as a daemon process, the name of the service is firewalld , which can define a set of rules to control the network access of the external incoming system.

Security Group Settings

However, in order to simplify the security use, the cloud platform achieves the same function as the firewall through a visual management interface-security group.

Therefore, when using a cloud server, the firewall will be turned off and replaced with a security group.


How to test the port is enabled?

You can use nc or telnet to test it:

  • Use nc

    # Success
    $ nc -zvw10 22
    Connection to 22 port [tcp/*] succeeded!

    # Failed
    $ nc -zvw10 9091
    nc: connect to port 9093 (tcp) failed: Connection refused

  • Use telnet

    # Success
    $ telnet 22
    Connected to
    Escape character is '^]'.

    # Failed
    $ telnet 9091
    telnet: Unable to connect to remote host: Connection refused