linux centeros 7.4 modify the hostname

Change the hostname to server_3

1. Use the command to modify

hostnamectl set-hostname server_3

2. Modify the configuration file /etc/hostname

vi /etc/hostname

server_3
~                                                                                                                            
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~                                                                                                                            
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~                                                                                                                            
~                                                                                                                            
~                    

Restart to take effect