Posts

How to Record Your Work on the Command Line with the script(1) Command

Most Unix-like operating systems feature a script command. You can find its manual in script(1) (type man 1 script to access it). script records a transcript (“typescript,” not to be confused with the language TypeScript) of your current session in the command line.

The script command can be used as a way to log what you are doing in a shell session. It’s often used during troubleshooting, documentation, PCI compliance audits, security/remediation work, penetration tests, and other situations where it’s useful to record a play-by-play log of what you’re doing on the machine.

 

Practical Demonstration

 

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Git: Setting up a low-requirements, personal Git repository

In this tutorial you will learn how to  how to quickly set up a simple, low-requirements, no-database, no-webserver Git repository. All you need is (unprivileged) SSH access and the git program itself.

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Shell Aliases

When working on Linux and Unix systems, you’ll often find yourself using long shell commands that you repeat several times per day (or per session). Things like

  • checking on the current resource usage of a system,
  • checking if a process has completed yet, or
  • using a complex group of commands, piped together with special options to give you just the output you want.

Generally, you’ll either use CTRL+R to search for these past commands in the shell’s history. Some of you may even copy useful commands to a special file that you can easily reference. You might even just enter them manually each time you need them, since you’re too lazy to be bothered.

There’s a simple solution that covers all of these cases well: Aliases.

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How to convert an SSH2 Public Key into an OpenSSH public key

When working with people who don’t use a Unix-based operating system, you’ll often come across the SSH2 Public Key format. PuTTY is probably the most famous software using this format and nearly everyone on Windows uses it. To give them access to a system, SFTP server, Git repository or similar you often need to convert an SSH2 public key into the OpenSSH format. This article describes how to do exactly that.

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Finding out what’s happening on a Linux Machine

Here’s a quick video on finding out what’s going on when you log into (or sit down at) a Linux machine. We cover the following commands:

w (/who): find out who is currently logged into the machine, and where they're connecting from

top: find out which processes are running, how much load they're putting on the CPU, and how much memory they're using.

(sudo) netstat -tulpn: Check for listening network ports and which processes/programs are using them.

Some Alternatives to the Tools I show in this Video:

I really like a program called htop, which shows you a bit more information and presents it in a nicer format. I recommend using it, once you’re comfortable with top.

htop (sudo apt-get install htop -- quit with 'ctrl-c' or 'q' once it's running)

Have fun!

The Absolute Basics: Set up a Linux Virtual Machine and get started

Everyone has to start their Linux System Administration journey somewhere. If you’re ready to dive into Linux, here are the absolute basics.

Install Linux in a Virtual Machine

First things first: you need to get a learning environment set up for yourself: a place where you can make mistakes, explore things, and hack the matrix without destroying your day-to-day environment. The answer? A virtual machine! Here’s a video detailing how to set up a Linux virtual machine:

 

Get Started on the Linux Command-Line

Next, the fun part — jumping into the command-line! Open up a terminal in Ubuntu (by pressing the windows key to bring up the application launcher, and then typing in ‘terminal’ to bring up the application), and let’s get started with your first few commands:

At this point, you’ve got your learning environment set up. You’re probably excited to dive in and begin learning, but take a few minutes to play around with Linux until you’re comfortable using the Graphical User Interface (GUI), and typing in the basic commands we’ve discussed so far.

From here, you can continue the Linux Sysadmin Basics YouTube playlist!