Lab
A Cloud Guru

Working with Essential Red Hat Linux System Administration Tools

In this lab we are going to make sure we have the minimum knowledge required to successfully pass the RHCE on RHEL8. We're going to present a scenario that will test an exam candidate's knowledge of how to use `grep` and configure `ssh` to help students succeed at this exam. *This course is not approved or sponsored by Red Hat.*

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Path Info

Level

Beginner

Duration

15m

Published

Oct 18, 2019

Challenge

Find the Username That the Other Admin Created

There are over 25,000 lines in /tmp/logfile so we don't want to do it by hand. While we don't know the exact format we're searching for, we're fairly confident that it's some form of the word "username".

grep -e 'user.*name' -i /tmp/logfile

That will match any iteration of 'user', followed by any character (or no character), followed by 'name'.
Challenge

Create an SSH Key

Use the command ssh-keygen to generate a key that we can use to copy to the other server to allow passwordless connections.
Challenge

Copy the SSH Key to Both cloud_user and the User Whose Name You Discovered in the First Task
Use the ssh-copy-id command to copy the SSH key to both the cloud_user and the new user name:
```
[cloud_user@Server1 ]# ssh-copy-id cloud_user@&ltServer2_INTERNAL_IP_ADDRESS>
[cloud_user@Server1 ]# ssh-copy-id &ltUSERNAME>@&ltServer2_INTERNAL_IP_ADDRESS>
```
Now we can test with two ssh commands:
```
ssh cloud_user@&ltServer2_INTERNAL_IP_ADDRESS&gt
```
Back out of that login, and try it for the other user:
```
ssh &ltUSERNAME&gt@&ltServer2_INTERNAL_IP_ADDRESS&gt
```
Just be sure you've substituted the correct Server2_INTERNAL_IP_ADDRESS and USERNAME in the commands. We should now be able to perform passwordless ssh logins.
Challenge

Ensure That No One Can Use a Password to Log into Server2
Now get out of that shell and come back in as cloud_user. Once we've logged in, we need to edit /etc/ssh/sshd_config and, with whichever text editor we like best, change the PasswordAuthentication variable to no. We're using vi as an example here:
```
[cloud_user@Server2 ]# sudo vi /etc/ssh/sshd_config
```
Once we've done that, restart the SSH daemon using sudo systemctl restart sshd.

To test, try to log in with a password:
```
[cloud_user@Server2 ]# ssh -o PreferredAuthentications=password cloud_user@localhost
```

Author

A Cloud Guru

The Cloud Content team comprises subject matter experts hyper focused on services offered by the leading cloud vendors (AWS, GCP, and Azure), as well as cloud-related technologies such as Linux and DevOps. The team is thrilled to share their knowledge to help you build modern tech solutions from the ground up, secure and optimize your environments, and so much more!

What's a lab?

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.