Managing User Accounts on Your Linux Instance

Each Linux instance type launches with a default Linux system user account. For Amazon Linux 2 or the Amazon Linux AMI, the user name is ec2-user. For Centos, the user name is centos. For Debian, the user name is admin or root. For Fedora, the user name is ec2-user or fedora. For RHEL, the user name is ec2-user or root. For SUSE, the user name is ec2-user or root. For Ubuntu, the user name is ubuntu. Otherwise, if ec2-user and root don't work, check with your AMI provider.

NOTE: Linux system users should not be confused with AWS Identity and Access Management (IAM) users. For more information, see IAM Users and Groups in the IAM User Guide.

Best Practice

Using the default user account is adequate for many applications, but you may choose to add user accounts so that individuals can have their own files and workspaces. Creating user accounts for new users is much more secure than granting multiple (possibly inexperienced) users access to the default user account, because that account can cause a lot of damage to a system when used improperly. For more information, see Tips for Securing Your EC2 Instance.

Creating a User Account

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


To add a user account

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

sudo adduser newuser

[Ubuntu] When adding a user to an Ubuntu system, include the --disabled-password parameter with this command to avoid adding a password to the account.

sudo adduser newuser --disabled-password

Switch to the new account so that the directory and file that you will create will have the proper ownership.

Add the SSH public key to the user account. 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.

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.

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.

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

[newuser ~]$ nano .ssh/authorized_keys

Paste the public key for the key pair into the file and save the changes. For example:

ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAABAQClKsfkNkuSevGj3eYhCe53pcjqP3maAhDFcvBS7O6V hz2ItxCih+PnDSUaw+WNQn/mZphTk/a/gU8jEzoOWbkM4yxyb/wB96xbiFveSFJuOp/d6RJhJOI0iBXr lsLnBItntckiJ7FbtxJMXLvvwJryDUilBMTjYtwB+QhYXUMOzce5Pjz5/i8SeJtjnV3iAoG/cQk+0FzZ qaeJAAHco+CY/5WrUBkrHmFJr6HcXkvJdWPkYQS3xqC0+FmUZofz221CBt5IMucxXPkX4rWi+z7wB3Rb BQoQzd8v7yeb7OzlPnWOyN0qFU0XA246RA8QFYiCNYwI3f05p6KLxEXAMPLE

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

Removing a User Account

If a user account is no longer needed, you can remove that account so that it may no longer be used.

To remove a user from the system

Use the userdel command to remove the user account from the system. When you specify the -r parameter, the user's home directory and mail spool are deleted. To keep the user's home directory and mail spool, omit the -r parameter.

[ec2-user ~]$ sudo userdel -r olduser

Credit: ( This article is copied from AWS document server).  I have presented here only as know how. 


Anup Chhetri

IT system administrator

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