Welcome Back to Linux Quick Notes!

Hello and welcome to the relaunched Linux Quick Notes! I’m Steven, and I’m thrilled to revive this blog, originally created four years ago during my first attempt at the CompTIA Linux+ certification. Back then, it was called Poker Notes—a placeholder title from a different project. Now, it’s rebranded as Linux Quick Notes to document my journey toward the Linux+ XK0-005 exam while keeping my skills sharp in retirement.

This blog will be a mix of:

• Study Notes: Breaking down Linux+ topics like file systems, scripting, and security for beginners and fellow learners.

• Command Cheat Sheets: Quick-reference tables for commands like ls, chmod, or systemctl.

• Practice Labs: Hands-on guides, like setting up a Rocky VM for testing systemd.

• Exam Tips: Strategies to tackle XK0-005’s performance-based questions.

Join me as I share what I learn, from revisiting basics (like my old notes on /etc) to mastering new topics like containers and automation. Whether you’re studying for Linux+ or exploring Linux, I hope these posts help you as much as they’ll help me! First up: a post on file permissions, coming soon.

Updating the bash $PATH variable

 When writing scripts, you usually want to store them in a folder that is defined in the bash $PATH variable. For example, you might want to create a 'bin' directory in your /home/user/ directory. Typing the following command will check to see if the directory already exists and if not it will go ahead and create it:

Here's a great article explaining how to make this PATH variable permanent:

Updating the PATH variable:

Login Monitoring

Here are a few helpful commands that will allow you to keep track of user login status of your Linux system. The first two commands are pretty straight forward: whoami and logname 

 

These two commands show that I'm currently working as sziegenbusch. At first glance there doesn't seem to be much difference between these two commands, however, when I switch user to kingtux I can see the difference.

 

 

 

 

 

I run whoami and learn that I'm current using the kingtux account, however, when I run the logname command I see that I'm sziegenbusch.

Another helpful command you can use to display who is logged in and related data (e.g., processes, boot time) is who

You can use the who command with the -a and -H options to see all available information and column headers:

The w command also displays who is logged on and the processes. You can read more information about the w command at The w command. 

The id command will show you a lot of information regarding your current user or an arbitrary user:

Other helpful commands for monitoring log in information are: lastlog, last -F, and lastb.

Force users to change their linux passwords

Building on the previous post regarding tldr I decided to use the chage command to force a user to change his password. In this example, I'm forcing the user kingtux to change his password at his next login attempt:

Now I'm going to login as kingtux:

 

Now I'm going to force the user kingtux to change his password using the passwd command:

 

Now I'll log in kingtux again:

The nice thing about Linux is that there is usually more than one way to get a job done. Use either: chage or passwd to force users to change their passwords.

Installing tldr on CS8

I installed a nice little application called "tldr." You can think of it as  "man pages" lite. In order to install it I had to install nodeJS and npm first. I followed the procedures on this page:

nodeJS and npm

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Then I installed tldr following these directions:

Tecmint tldr

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Here's a screen shot of using tldr to lookup help for the chage command:

Centos Stream 8

 I loaded Centos Stream 8 (CS8) today in order to learn RHEL using RHEL closest clone out there. Here's what I've done so far: 

1) I downloaded and installed CS8 in VirtualBox, 

2) I ran # dnf check-update and dnf update

3) installed VB Guest Additions using the procedure found on:

Tecmint How-Tos

Setting the "hostname" of the machine.

 Here's a good article by Red Hat that list seven ways to set a machine's hostname:

Update hostnames

When just using: hostnamectl with no arguments you get this print out: