Change a Linux server's hostname

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By default, your server is started with the server's given name as the hostname.
Some software such as cPanel® requires a valid fully qualified domain name (FQDN) for the hostname
to be used during their licensing verification system. This article describes how to change a server hostname
in Linux®.

Change a server's hostname

Check existing hostname
```
$ hostname
```
Modify the value to match your FQDN hostname,
as shown in the following example:
```
$  hostnamectl set-hostname NEW-HOST
$  hostname
NEW-HOST
```
Open the file at /etc/hosts. To update the information for internal
networking, change the host that is associated with the main IP address
for your server, as shown in the following example:
```
$  vim /etc/hosts    
127.0.0.1      localhost localhost.localdomain
123.45.67.89   hostname.domain.com   hostname
```

Change the domain name (where required)

$  vim /etc/resolv.conf
domain abc.com            <--- This would be the domain.
nameserver 173.203.4.8
nameserver 173.203.4.9

Change networking configuration /etc/sysconfig/network

$  vim /etc/sysconfig/network
NETWORKING=yes
FORWARD_IPV4=false
HOSTNAME=hostname.domainname.com   <---- change this bit (FQDN)
DOMAINNAME=domainname.com          <---- change this bit if the domain name has changed
GATEWAY=172.0.0.1
GATEWAYDEV=eth0

Change networking configuration /etc/sysconfig/network
```
$  vim /etc/hostname
hostname.domainname.com
```

Update the Mail Transfer Agent (MTA) configuration.

$  vim /etc/postfix/mydomains
mydomains - included a list of aliases for your machine here, formatted:
example.com                                   OK
After change, run 'postmap /etc/postfix/mydomains'
localhost                                     OK
#myoldserver.domain.com                       OK <------ commented out
myserver.domain.com                           OK <----- added in

Update the hostname in Postfix if it is hadcoded in and restart the service

$  vim /etc/postfix/main.cf
$  postmap /etc/postfix/main.cf
$  systemctl restart postfix

NOTE: This file can have quite a bit of information. You can grep for 'hostname' for faster results.

$  grep 'hostname' /etc/postfix/main.cnf
$  cat /etc/postfix/main.cnf | grep hostname

Update MySQL, MariaDB or Percona - Check the user table for the old hostname.
```
$  mysql -e "SELECT DISTINCT host FROM mysql.user;"
```
If binary logging is enabled and the log files named using the original hostname then you must update /etc/my.cnf or binary logging will break and possibly have replication. You must specify the filename of the existing files, i.e. the old hostname
```
$  grep  -E 'log-bin|relay-log' /etc/my.cnf /etc/mysql/my.cnf
log-bin=/var/lib/mysqllogs/oldlogfilename
relay-log=/var/lib/mysqllogs/oldrelaylogfilename
```

Restart syslog

$  service rsyslog restart    
or
$  systemctl restart rsyslog

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Updated about 1 year ago

Change a server's hostname

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