As I mentioned in some of my previous articles from the #3MonthsOfCloudDevOps series, I recently started working with Linux and Linux commands.

It has been a continuous learning curve and I wanted to highlight some of the commands (and packages) I have used so far.

Apart from the basic commands, this article will highlight others that have been extremely useful in resolving Linux-related issues. I will most likely keep adding to this article as time goes by, so I can always come back to them as a reference.

Let's go!

Package installers/managers

These managers are probably the ones I made the most mistakes with. I always have to remind myself when to use what.

• apt (Advanced Packaging Tool): I used this when working within Ubuntu-based EC2 instances.

• yum (Yellowdog Updater, Modified): This was the packager manager I used whenever I was working with amazon/aws-cli Docker image (or the AWS circleCI orb); basically AWS-CLI related installations.

• apk (Alpine Package Keeper): Mostly used this with CircleCI config files when working with alpine-related Docker images.

The Others - ssh, wget, tar, gzip, etc

I am not sure how to classify most of these, so I would just list them:

• ssh: start a secure connection to the SSH server on a remote machine. I used the command for connecting to EC2 instances from my machine.

• nano: command line text editor. Another option is vim but so far, I've only tried nano.

• wget: retrieve files from the internet. I used this command quite a number of times for installations that required fetching compressed/archived files and extracting them.

• tar: extracting and compressing files. Mostly used with files I fetched with wget, and in conjunction with gzip.

• grep: command line utility for searching for characters in files. This one has helped me a whole lot!

• chmod: change access permissions of files and directories. Mostly used on AWS key files whenever I try to ssh into EC2 instances.

System utilities

• launchctl: systemctl but for MacOS.

• tee: I personally used this when I wanted to append the output of a command that read the contents of a file to a file.

Basic syntax is [command] | tee [options] [filename].

Command Chunks

Quick commands for some common issues:

1) Create new files

There are just so many ways to do this, so I'm jotting down my go-tos:

a) echo > [newfile]

b) cat [file] > [newfile] : when you want to create a copy of a file as another file.

2) List all users accounts

Ubuntu/Linux: cut -d: -f1 /etc/passwd

macOS: dscl . list /Users | grep -v “^_”

3) Fix "port in use" issue

a) find the process id (pid) for the port: lsof -i :[port]

b) free the port: sudo kill -9 <pid>

I'll keep updating but I hope it helps save your time as well!