Begin by opening the configuration file with your text editor as root:

# nano /etc/ssh/sshd_config

The first option that you may want to change is the port that SSH runs on. Find the line that looks like this:

#Port 22

Change this to a different port

#Port 2244

Reload ssh

# systemctl reload sshd.service

After saving, don’t exit until you’ve completed these steps.

By default, SELinux only allows port 22 for SSH. What you need to do is enable the newly created port through SELinux. To do that, run the commands below

# sudo semanage port -a -t ssh_port_t -p tcp 2244

If you run the commands above and get an error that semanage command not found, run the commands below to install it.

# sudo yum -y install policycoreutils-python

Then go and run the semange commend again to allow the new port through SELinux.

Note: CentOS8

In CentOS or RHEL Linux based distributions, install policycoreutils package and add the below rules to relax SELinux policy in order for the SSH daemon to bind on the new port.

# yum install policycoreutils
# semanage port -a -t ssh_port_t -p tcp 34627
# semanage port -m -t ssh_port_t -p tcp 34627
# systemctl restart sshd
# netstat -tlpn| grep ssh
# ss -tlpn| grep ssh

After that, run the commands below to allow the new port through the firewall.

# sudo firewall-cmd --permanent --zone=public --add-port=2244/tcp

Reload the firewall configurations

# sudo firewall-cmd --reload

Restart SSH by running the commands below.

# sudo systemctl restart sshd.service