Locking Down Remote Access to Linux

30 minutes
  • 2 Learning Objectives

About this Hands-on Lab

In this lab, we will look at how to lock down remote access to a Linux host. We will accomplish this by restricting all remote logins for the `root` account as well as restricting SSH access based on account names.

Learning Objectives

Successfully complete this lab by achieving the following learning objectives:

Prevent remote logins from using the `root` account.
  1. In order to prevent remote logins from using the root account, we’ll need to edit the /etc/passwd file. Run the following command:

    sudo vipw 
    • select #2 for nano (easiest)
  2. Next, edit the line that starts with root and replace /bin/bash with /sbin/nologin.

  3. Save and exit the /etc/passwd file.

Permit only the `cloud_user` account to connect to the host via SSH.
  1. In order to filter SSH access and only permit the cloud_user account to access the host via SSH, we’ll need to edit the sshd_config file with the following command:

    sudo nano /etc/ssh/sshd_config
  2. Add the following line to the file just under the second line of the file:

    AllowUsers cloud_user

    Note: You can also restrict user access by source hostname, IP address, or subnet, like:

    AllowUsers cloud_user@
    AllowUsers Jhalpert@james.host.int
    AllowUsers mscott@
  3. Now, restart the ssh service with the following command:

    sudo service ssh restart

Additional Resources

You have been asked to lock down remote access to a new Linux server. Your supervisor has requested you prevent all remote logins for the root account and only permit remote SSH access for the cloud_user account.

What are Hands-on Labs

Hands-on Labs are real environments created by industry experts to help you learn. These environments help you gain knowledge and experience, practice without compromising your system, test without risk, destroy without fear, and let you learn from your mistakes. Hands-on Labs: practice your skills before delivering in the real world.

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