How to modify hostname by CentOS or RHEL 7

This article is about how CentOS or RHEL 7 modifies host names. The editor thinks it is very practical, so share it with you as a reference and follow the editor to have a look.

Question: what is the correct way to change the hostname on CentOS/RHEL 7 (permanent or temporary)?

In CentOS or RHEL, there are three defined hostnames:

A. static (static)

B, transient (transient)

C, flexible (pretty)

The "static" hostname, also known as the kernel hostname, is the hostname that the system initializes automatically from / etc/hostname at startup. The "transient" hostname is a hostname temporarily assigned while the system is running, for example, through a DHCP or mDNS server. Both static and transient hostnames follow the same character restrictions as Internet domain names. "flexible" hostnames, on the other hand, allow the use of free-form hostnames (including special / white space characters) to be presented to end users, such as Dan's Computer.

In CentOS/RHEL 7, there is a command-line tool called hostnamectl that allows you to view or modify configurations related to hostnames.

To view settings related to the hostname:

$hostnamectl status

View only static, transient, or flexible hostnames, using the "--static", "--transient", or "--pretty" options, respectively.

$hostnamectl status [--static |-- transient |-- pretty]

To modify all three hostnames at once: static, transient, and flexible hostnames:

$sudo hostnamectl set-hostname

As shown above, when you modify a static / transient hostname, any special or white space characters are removed, and any uppercase letters in the supplied parameters are automatically converted to lowercase. Once the static hostname is modified, / etc/hostname will be updated automatically. However, / etc/hosts will not be updated to save your changes, so you need to update / etc/hosts manually.

If you only want to change a specific hostname (static, transient, or flexible), you can use the "--static", "--transient" or "--pretty" options.

For example, to permanently change the hostname, you can modify the static hostname:

$sudo hostnamectl-staticset-hostname

Note that you do not have to restart the machine to activate permanent hostname modification. The above command immediately modifies the kernel hostname. Log out and log back in to observe the new static hostname at the command line prompt.

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