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manage-users-on-your-linux.md

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Manage users on your Linux instance

In AWS, each Linux instance launches with a default Linux system user. You can add users to your instance and delete users.

For the default user, the default user name is determined by the AMI that was specified when you launched the instance.

Default user names

The default user name for your EC2 instance is determined by the AMI that was specified when you launched the instance.

The default user names are:

For Amazon Linux 2023, Amazon Linux 2, or the Amazon Linux AMI, the user name is ec2-user.

  • For a CentOS AMI, the user name is centos or ec2-user.
  • For a Debian AMI, the user name is admin.
  • For a Fedora AMI, the user name is fedora or ec2-user.
  • For a RHEL AMI, the user name is ec2-user or root.
  • For a SUSE AMI, the user name is ec2-user or root.
  • For an Ubuntu AMI, the user name is ubuntu.
  • For an Oracle AMI, the user name is ec2-user.
  • For a Bitnami AMI, the user name is bitnami.
  • Otherwise, check with the AMI provider.

Considerations

Using the default user is adequate for many applications. However, you may choose to add users so that individuals can have their own files and workspaces. Furthermore, creating users for new users is much more secure than granting multiple (possibly inexperienced) users access to the default user, because the default user can cause a lot of damage to a system when used improperly.

To enable users SSH access to your EC2 instance using a Linux system user, you must share the SSH key with the user. Alternatively, you can use EC2 Instance Connect to provide access to users without the need to share and manage SSH keys.

Create a user

First create the user, and then add the SSH public key that allows the user to connect to and log into the instance.

To create a user

  1. Create a new key pair. You must provide the .pem file to the user for whom you are creating the user. They must use this file to connect to the instance.

  2. Retrieve the public key from the key pair that you created in the previous step.

$  ssh-keygen -y -f /path_to_key_pair/key-pair-name.pem

The command returns the public key, as shown in the following example.

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQClKsfkNkuSevGj3eYhCe53pcjqP3maAhDFcvBS7O6Vhz2ItxCih+PnDSUaw+WNQn/mZphTk/a/gU8jEzoOWbkM4yxyb/wB96xbiFveSFJuOp/d6RJhJOI0iBXrlsLnBItntckiJ7FbtxJMXLvvwJryDUilBMTjYtwB+QhYXUMOzce5Pjz5/i8SeJtjnV3iAoG/cQk+0FzZqaeJAAHco+CY/5WrUBkrHmFJr6HcXkvJdWPkYQS3xqC0+FmUZofz221CBt5IMucxXPkX4rWi+z7wB3RbBQoQzd8v7yeb7OzlPnWOyN0qFU0XA246RA8QFYiCNYwI3f05p6KLxEXAMPLE

  1. Connect to the instance.

  2. Use the adduser command to create the user and add it to the system (with an entry in the /etc/passwd file). The command also creates a group and a home directory for the user. In this example, the user is named newuser.

  • Amazon Linux and Amazon Linux 2

With Amazon Linux and Amazon Linux 2, the user is created with password authentication disabled by default.

[ec2-user ~]$ sudo adduser newuser
  • Ubuntu

Include the --disabled-password parameter to create the user with password authentication disabled.

[ubuntu ~]$ sudo adduser newuser --disabled-password
  1. Switch to the new user so that the directory and file that you create will have the proper ownership.
[ec2-user ~]$ sudo su - newuser

The prompt changes from ec2-user to newuser to indicate that you have switched the shell session to the new user.

  1. Add the SSH public key to the user. First create a directory in the user's home directory for the SSH key file, then create the key file, and finally paste the public key into the key file, as described in the following sub-steps.

a. Create a .ssh directory in the newuser home directory and change its file permissions to 700 (only the owner can read, write, or open the directory).

[newuser ~]$ mkdir .ssh
[newuser ~]$ chmod 700 .ssh

Important: Without these exact file permissions, the user will not be able to log in.

b. Create a file named authorized_keys in the .ssh directory and change its file permissions to 600 (only the owner can read or write to the file).

[newuser ~]$ touch .ssh/authorized_keys
[newuser ~]$ chmod 600 .ssh/authorized_keys

Important: Without these exact file permissions, the user will not be able to log in.

c. Open the authorized_keys file using your favorite text editor (such as vim or nano).

[newuser ~]$ nano .ssh/authorized_keys

Paste the public key that you retrieved in Step 2 into the file and save the changes.

Important: Ensure that you paste the public key in one continuous line. The public key must not be split over multiple lines.

The user should now be able to log into the newuser user on your instance, using the private key that corresponds to the public key that you added to the authorized_keys file.