How to use Linode?

Today, I Buy linode VPS

But, I before login, I change the VPS OS and login it again.
I see this error info:


how to resolve it?

in your PC

cd .ssh
rm -rf known_hosts
touch known_hosts

Now you can use 
ssh root@ip
login it !

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Centos 7 how to start FireWall?

Enable Firewalld

To enable firewalld, run the following command as root:

systemctl enable firewalld

Start Firewalld

To start firewalld, run the following command as root:

systemctl start firewalld

Check the Status of Firewalld

To check the status of firewalld, run the following command as root:

systemctl status firewalld

Ok  it works for me!

Thanks to:
https://www.digitalocean.com/community/questions/warning-remote-host-identification-has-changed

how to start firewall in Centos 7
http://www.liquidweb.com/kb/how-to-start-and-enable-firewalld-on-centos-7/