Change the hostname of your AL2 instance - Amazon Linux 2
Change the system hostnameChange the shell prompt without affecting the hostnameChange the hostname on other Linux distributions
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Change the hostname of your AL2 instance

When you launch an instance into a private VPC, Amazon EC2 assigns a guest OS hostname. The type of hostname that Amazon EC2 assigns depends on your subnet settings. For more information about EC2 hostnames, see Amazon EC2 instance hostname types in the Amazon EC2 User Guide.

A typical Amazon EC2 private DNS name for an EC2 instance configured to use IP-based naming with an IPv4 address looks something like this: ip-12-34-56-78.us-west-2.compute.internal, where the name consists of the internal domain, the service (in this case, compute), the region, and a form of the private IPv4 address. Part of this hostname is displayed at the shell prompt when you log into your instance (for example, ip-12-34-56-78). Each time you stop and restart your Amazon EC2 instance (unless you are using an Elastic IP address), the public IPv4 address changes, and so does your public DNS name, system hostname, and shell prompt.

Important

This information applies to Amazon Linux. For information about other distributions, see their specific documentation.

Change the system hostname

If you have a public DNS name registered for the IP address of your instance (such as webserver.mydomain.com), you can set the system hostname so your instance identifies itself as a part of that domain. This also changes the shell prompt so that it displays the first portion of this name instead of the hostname supplied by Amazon (for example, ip-12-34-56-78). If you do not have a public DNS name registered, you can still change the hostname, but the process is a little different.

In order for your hostname update to persist, you must verify that the preserve_hostname cloud-init setting is set to true. You can run the following command to edit or add this setting:

sudo vi /etc/cloud/cloud.cfg

If the preserve_hostname setting is not listed, add the following line of text to the end of the file: 

preserve_hostname: true
To change the system hostname to a public DNS name

Follow this procedure if you already have a public DNS name registered.

    • For AL2: Use the hostnamectl command to set your hostname to reflect the fully qualified domain name (such as webserver.mydomain.com).

      [ec2-user ~]$ sudo hostnamectl set-hostname webserver.mydomain.com

    • For Amazon Linux AMI: On your instance, open the /etc/sysconfig/network configuration file in your favorite text editor and change the HOSTNAME entry to reflect the fully qualified domain name (such as webserver.mydomain.com).

      HOSTNAME=webserver.mydomain.com

  2. Reboot the instance to pick up the new hostname.

    [ec2-user ~]$ sudo reboot

    Alternatively, you can reboot using the Amazon EC2 console (on the Instances page, select the instance and choose Instance state, Reboot instance).

  3. Log into your instance and verify that the hostname has been updated. Your prompt should show the new hostname (up to the first ".") and the hostname command should show the fully-qualified domain name.

    [ec2-user@webserver ~]$ hostname
webserver.mydomain.com
To change the system hostname without a public DNS name

    • For AL2: Use the hostnamectl command to set your hostname to reflect the desired system hostname (such as webserver).

      [ec2-user ~]$ sudo hostnamectl set-hostname webserver.localdomain

    • For Amazon Linux AMI: On your instance, open the /etc/sysconfig/network configuration file in your favorite text editor and change the HOSTNAME entry to reflect the desired system hostname (such as webserver).

      HOSTNAME=webserver.localdomain

  2. Open the /etc/hosts file in your favorite text editor and change the entry beginning with 127.0.0.1 to match the example below, substituting your own hostname.

    127.0.0.1 webserver.localdomain webserver localhost4 localhost4.localdomain4

  3. Reboot the instance to pick up the new hostname.

    [ec2-user ~]$ sudo reboot

    Alternatively, you can reboot using the Amazon EC2 console (on the Instances page, select the instance and choose Instance state, Reboot instance).

  4. Log into your instance and verify that the hostname has been updated. Your prompt should show the new hostname (up to the first ".") and the hostname command should show the fully-qualified domain name.

    [ec2-user@webserver ~]$ hostname
webserver.localdomain

You can also implement more programmatic solutions, such as specifying user data to configure your instance. If your instance is part of an Auto Scaling group, you can use lifecycle hooks to define user data. For more information, see Run commands on your Linux instance at launch and Lifecycle hook for instance launch in the Amazon CloudFormation User Guide.

Change the shell prompt without affecting the hostname

If you do not want to modify the hostname for your instance, but you would like to have a more useful system name (such as webserver) displayed than the private name supplied by Amazon (for example, ip-12-34-56-78), you can edit the shell prompt configuration files to display your system nickname instead of the hostname.

To change the shell prompt to a host nickname

  1. Create a file in /etc/profile.d that sets the environment variable called NICKNAME to the value you want in the shell prompt. For example, to set the system nickname to webserver, run the following command.

    [ec2-user ~]$ sudo sh -c 'echo "export NICKNAME=webserver" > /etc/profile.d/prompt.sh'

  2. Open the /etc/bashrc (Red Hat) or /etc/bash.bashrc (Debian/Ubuntu) file in your favorite text editor (such as vim or nano). You need to use sudo with the editor command because /etc/bashrc and /etc/bash.bashrc are owned by root.

  3. Edit the file and change the shell prompt variable (PS1) to display your nickname instead of the hostname. Find the following line that sets the shell prompt in /etc/bashrc or /etc/bash.bashrc (several surrounding lines are shown below for context; look for the line that starts with [ "$PS1"):

      # Turn on checkwinsize
  shopt -s checkwinsize
  [ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@\h \W]\\$ "
  # You might want to have e.g. tty in prompt (e.g. more virtual machines)
  # and console windows

    Change the \h (the symbol for hostname) in that line to the value of the NICKNAME variable.

      # Turn on checkwinsize
  shopt -s checkwinsize
  [ "$PS1" = "\\s-\\v\\\$ " ] && PS1="[\u@$NICKNAME \W]\\$ "
  # You might want to have e.g. tty in prompt (e.g. more virtual machines)
  # and console windows

  4. (Optional) To set the title on shell windows to the new nickname, complete the following steps.

    1. Create a file named /etc/sysconfig/bash-prompt-xterm.

      [ec2-user ~]$ sudo touch /etc/sysconfig/bash-prompt-xterm

    2. Make the file executable using the following command.

      [ec2-user ~]$ sudo chmod +x /etc/sysconfig/bash-prompt-xterm

    3. Open the /etc/sysconfig/bash-prompt-xterm file in your favorite text editor (such as vim or nano). You need to use sudo with the editor command because /etc/sysconfig/bash-prompt-xterm is owned by root.

    4. Add the following line to the file.

      echo -ne "\033]0;${USER}@${NICKNAME}:${PWD/#$HOME/~}\007"

  5. Log out and then log back in to pick up the new nickname value.

Change the hostname on other Linux distributions

The procedures on this page are intended for use with Amazon Linux only. For more information about other Linux distributions, see their specific documentation and the following articles: