Watching a tutorial and fixing a broken server in production are two different skills, and the gap is mostly hands-on time on real systems. You do not need a paid lab subscription or your own Kubernetes cluster to close that gap in 2026. A handful of free platforms put you in front of a real terminal with real failures.
What follows is a curated pass through the platforms still worth your time. The list is shorter than what you will find in most roundups because most of those pad with five-line vendor listings. Platforms are grouped by what they actually teach.
Where to start if you cannot start anywhere
If you have never used a Linux terminal for anything besides running git commit, the first platform you should look at is OverTheWire’s Bandit. Bandit is a wargame, a series of progressively harder puzzles, where you SSH (Secure Shell, an encrypted remote-login protocol) into a server and solve each level to get the password for the next one. There are 34 levels. The first ten teach navigation, file reading, hidden files, and basic shell commands. The middle ten cover SSH keys, port forwarding, and shell scripting. The later ones touch on basic cryptography.
The point of Bandit is not to make you a security researcher. The point is that you cannot pass level 12 without understanding how a process inherits file descriptors (kernel handles for open files, pipes, and sockets) from its parent. That single skill is more useful for DevOps than any certification, because every container and every systemd service runs on that exact mechanism.
The reason Bandit comes first is that it requires no setup at all. You need a terminal and an SSH client. macOS and Linux have both built in. Windows users can use Windows Terminal with the built-in OpenSSH client. There is no account to create, no payment, no install. If you have never SSHed into anything, ssh bandit0@bandit.labs.overthewire.org -p 2220 and the password bandit0 gets you started.
Where to go when tutorials stop helping
Tutorials teach you commands. Production teaches you that the commands are not the problem, the failure is. SadServers is the closest thing DevOps has to LeetCode, and it is the platform I would point any junior DevOps engineer at before they interview anywhere serious.
SadServers gives you a broken Linux or container environment, a one-paragraph problem statement, and a timer. Your job is to fix it. There is no walkthrough, no hints panel. You open a terminal, read the symptoms, and figure it out. The scenarios cover real production-style failures: a web server that refuses to start, a disk that fills up because of a runaway log file, a process that keeps getting OOM-killed (killed by the Linux out-of-memory killer when the system runs out of memory), a database that is rejecting connections because its bind address is misconfigured.
The library is community-submitted, so the variety is real. Some scenarios are beginner-friendly. Some are advanced. All of them are graded against a hidden test, so you know whether you actually fixed it or whether you just made the symptom go away.
Watching tutorials teaches you kubectl get pods. SadServers teaches you what to do when that returns a pod in CrashLoopBackOff and nobody left notes.
The platforms that pretend to be DevOps but are really Git
Learn Git Branching is a browser-based interactive tutorial that teaches Git through visual puzzles. You type real Git commands and watch the commit graph update in real time. It covers branching, rebasing, merging, cherry-picking, and reflog, the operations most engineers pretend to understand and secretly do not.
The catch is that Learn Git Branching is not a DevOps platform. It is a Git platform. The skills transfer, because almost every DevOps toolchain depends on Git, but you will not learn anything about containers, infrastructure, or networking here. Run through both the Main track and the Remote track in a single afternoon. It is the fastest payoff of any platform on this list.
If you already know what HEAD~2 means and you can rebase a feature branch without panicking, skip this one.
The all-purpose lab you will actually use
Killercoda is what most other roundups call “the best free DevOps practice platform,” and for once the hype is mostly deserved. Killercoda gives you a real Linux environment in your browser, with a real terminal connected to a real server. Choose a scenario, and within seconds you have an SSH session on a system that is configured for whatever the scenario is teaching.
The scenario library is the product. Hundreds of free scenarios cover Linux, Docker, Kubernetes, Ansible, ArgoCD, Terraform, Cilium, and more. Many are contributed by the tool vendors themselves, so Grafana’s official getting-started tutorial runs on Killercoda, and so does Cilium’s network policy lab. The free tier has session timeouts (you cannot leave and come back to a running environment), and some advanced scenarios are paywalled as “PLUS.” For 90% of what you would want to practice, the free tier is enough.
Want to learn ArgoCD applications? There is a scenario. Cilium network policies? There is a scenario. The cost of trying a new tool drops from “an afternoon of setup” to “click the scenario.”
Where to learn Docker and Kubernetes without installing anything
Play with Docker and Play with Kubernetes are sibling platforms run by Docker, Inc. They give you a free, 4-hour Linux instance in the cloud. Play with Docker includes a real Docker daemon, multiple instances for practicing Swarm or multi-container networking, and it is what the official Docker documentation uses for its interactive examples. Play with Kubernetes gives you a real multi-node Kubernetes cluster, control plane and worker nodes, where you can run deployments, services, configmaps, namespaces, and RBAC (role-based access control).
Both have the same catch: the session expires after 4 hours. That is fine for learning fundamentals, less fine for anything that needs to run overnight. Both are also best for first contact with the tool. Once you know what kubectl apply does, you will want minikube or kind (Kubernetes in Docker, a tool that runs a local K8s cluster inside Docker containers) on your own laptop so you can experiment without a clock ticking.
If you are deciding between Play with Kubernetes and minikube, start with Play with Kubernetes. The browser-based cluster teaches you how a real multi-node cluster bootstraps, which minikube hides from you. Then move to minikube when you want to run long experiments.
The Linux internals course nobody tells juniors about
pwn.college is run by Arizona State University and teaches Linux internals through structured challenges. The entry point for DevOps practitioners is the “Linux Luminarium” track. It covers how the shell actually works, process interactions, file descriptors, environment variables, and privilege escalation, the concepts that underpin every container and every systemd unit but are rarely taught explicitly.
Containers are Linux primitives. When you understand what a file descriptor is and what happens when a process calls fork() and exec(), Docker stops being a black box. When you understand cgroups (control groups, the kernel feature that limits CPU, memory, and I/O for a group of processes) and namespaces (the kernel feature that gives a process its own view of the filesystem, network, and process table), Kubernetes networking stops being magic. The platform is university-quality and completely free, with a Discord channel staffed by the instructors.
The late modules lean toward CTF (capture-the-flag, competitive security puzzles) and exploit development, which is past what most DevOps engineers need. The Linux Luminarium track is the part that matters here.
The pair that takes a full weekend
If you finish Play with Kubernetes and you want to know what that bootstrap process was actually doing, the next step is Kubernetes The Hard Way by Kelsey Hightower. It is a guided walkthrough where you bootstrap a Kubernetes cluster by hand, without kubeadm (the official Kubernetes bootstrap tool), without a managed cloud provider, without any of the conveniences. You generate the certificates yourself, you configure the etcd cluster yourself, you wire up the API server yourself.
The Hard Way is not interactive in the same way as the platforms above. It is a guide. You follow it on your own hardware or on cloud VMs (virtual machines), and you learn what every other Kubernetes installation tool is hiding from you. Pair it with Play with Kubernetes and you will understand both the convenience and the cost of every cluster abstraction above it.
Most DevOps engineers I have spoken to who actually understand Kubernetes did The Hard Way once. It is the closest thing to a free replacement for a CKA (Certified Kubernetes Administrator) bootcamp.
Trade-offs
The free tier of every platform on this list has trade-offs.
- Session timeouts. Killercoda, Play with Docker, Play with Kubernetes all expire after a few hours. You cannot run a long experiment and come back to it.
- No persistent state. When the session ends, the work is gone. The platforms are for practicing concepts, not for building anything you want to keep.
- No structured paths. Most platforms are scenario libraries, not courses. You pick what to do, in whatever order. If you need someone to tell you what to learn next, look at a paid curriculum.
- Vendor scenarios can be marketing. Some Killercoda scenarios are written by the vendor of the tool. The bias is usually light, but it is there. Cross-check against the tool’s own documentation.
- Linux is assumed. Every platform on this list expects you to be comfortable in a Linux terminal. Start with Bandit first if that is not you.
If your goal is to pass a specific certification (CKA, CKAD, RHCE), the free platforms are good for concept practice but they are not a substitute for the official exam objectives. Use them to build intuition, then drill on the official curriculum.
If your goal is to be less afraid when something breaks in production, these are the closest free thing to that experience. Start with Bandit if you are new to the terminal, SadServers if you are not.
What I would tell past me
If I could go back and tell the version of me who thought watching PluralSight courses was enough, three things:
- Watching is not practicing. The single biggest gap is doing things with your hands. SadServers exists for this reason.
- Containers are Linux primitives. If you do not understand file descriptors, cgroups, and namespaces, you do not understand containers. pwn.college’s Linux Luminarium track is the fastest free way to fix that.
- The Hard Way teaches more than the easy way. Doing Kubernetes The Hard Way once, even if you never do it again, makes every managed cluster feel less magical.