6 Essential Linux Command Line Tools for DevOps Engineers

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Introduction¶

Practicing DevOps means juggling lots of various command line tools, kubectl, helm and other *.ctls from different cloud native projects. A good working knowledge of those command line tools is essential, but even more important are the command line tools used to _glue_ together the DevOps workflow.

Whether you’re managing deployments, automating tasks, or troubleshooting issues, a strong command of Linux tools is indispensable. As engineers, we constantly strive for efficiency and reliability, and the right set of tools can be a game-changer.

Linux commands are the backbone of many DevOps tasks. From configuration management to monitoring system performance, these commands streamline processes and enhance productivity. In this blog, we’ll explore six essential Linux commands that every DevOps engineer should know. These commands will not only simplify your day-to-day tasks but also empower you to handle complex scenarios with ease.

Let’s dive into these 6 essential Linux commands that will become your go-to tools in your DevOps toolkit.

1. yq — Parsing and Modifying YAML¶

Yq is a lightweight and portable command-line YAML processor. More information: yq.

YAML files are ubiquitous in DevOps, especially for configuration management. The yq command is a powerful tool for parsing and modifying these files. Let’s inspect a deployment configuration file using yq.

cat deploy-config.yaml

app:
  name: mywebapp
  version: 1.0.0
  image: nginx:latest
  replicas: 3
database:
  image: postgres:13
  password: secretpassword

Now, let’s extract the image used by our app:

yq '.app.image' deploy-config.yaml

This command will output:

nginx:latest

2. sed and grep — Updating Configuration¶

Sed allows to edit text in a scriptable manner. See also: awk, ed. More information: sed.

When it’s time for a new release, updating configuration files is a routine task. The combination of sed and grep makes this process seamless. Here’s how you can update the version in our YAML file:

sed -i 's/version: 1.0.0/version: 1.1.0/' deploy-config.yaml

grep version deploy-config.yaml

Find patterns in files using regular expressions. More information: GNU Grep Manual.

Sed will update the version, we can quickly grep to confirm the change.

3. curl — Checking Deployment Status¶

Transfers data from or to a server. Supports most protocols, including HTTP, FTP, and POP3. More information: curl manpage.

Monitoring the status of your deployment APIs is crucial. The curl command allows you to check API statuses and parse the responses. For example, to check the latest release of Kubernetes:

curl -s 'https://api.github.com/repos/kubernetes/kubernetes/releases/latest' | yq '.tag_name'

This will give us the tag name of the latest Kubernets release.

4. tee — Logging Deployment Steps¶

Keeping logs of your deployment steps ensures you have a trail of what was executed. The tee command is perfect for this:

echo 'Starting deployment process' | tee deployment.log
echo 'App version: 1.1.0' | tee -a deployment.log
cat deployment.log

5. watch — Monitoring Deployment Progress¶

Watch executes a program periodically, showing output. More information: watch.

The watch command is excellent for real-time monitoring. For example, by continuously watching the status of Kubernetes pods, you can stay updated on the deployment progress:

watch kubectl get pods

kubectl has its own — watch flag which we could use in this specific case:

kubectl get pods — watch

6. journalctl — Viewing System Logs¶

Since most of the time you will work with Linux based virtual machines, journald can query the systemd journal. More information: journalctl.

System logs are invaluable for troubleshooting. The journalctl command helps you view and filter these logs. For instance, to view logs for a specific service:

journalctl -u nginx.service | tail

Conclusion¶

Having those commands in your toolbelt and knowing when and how to use them can often mean a difference between spending 2 hours vs 30 min on a task. This is of course not an exhaustive list, but I find myself using those specific commands more often than others.

Do you agree with the list? Are there any other commands you find essential in your workflow?

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