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Exam Information
Official specifications published by Red Hat
Exam Format
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Skills this practice test covers
- Build an image from a Containerfile with the FROM, COPY, USER, WORKDIR and ENTRYPOINT instructions.
- Log in to registries, tag images with fully qualified names, and push and pull them.
- Back up an image with podman save and a container's file system with podman export.
- Run containers in detached mode, publish their ports and pass environment variables at run time.
- Start a multi-container application stack with shared volumes, secrets and service dependencies.
- Find faults with podman logs, podman inspect and podman exec on a running container.
Explore related topics
EX188 exam content
5 domains · 30 topics · 160 questions
Implement Images Using Podman and Containerfile46 questions
This domain is about writing a Containerfile and building an image from it. Candidates choose a base image, add content, set the user and working directory, expose ports, pass variables, set the start command and share host data safely.
Skills tested
- Choose a base image with the FROM instruction, such as a Universal Base Image.
- Copy content into the image with COPY or ADD, and set USER and WORKDIR.
- Pass build-time values with ARG and runtime settings with ENV.
- Set the start command with ENTRYPOINT and CMD, and expose the ports the service uses.
- Share host data through bind mounts with the :Z or :z option for SELinux.
Questions by topic
- Specify the Container Base Image9
- Add Content and Configure Runtime Environment10
- Configure Container Runtime Environment12
- Container Volumes and Host Data Sharing4
- Pass Environment Variables and Arguments4
- Expose Ports from a Containerfile2
- Specify the Command to Run in Custom Image3
- Security and Permissions for Host and Network Access2
Manage Images33 questions
This domain covers images after they are built: where they are stored, how they are named and how they move. Candidates log in to private registries, tag images, push and pull them, and back up images and container state.
Skills tested
- Log in to a private registry with podman login and keep the credentials in auth.json.
- Edit /etc/containers/registries.conf to set the registry search order and insecure registries.
- Tag images with fully qualified names instead of relying on the latest tag.
- Save an image with its layers and metadata using podman save, then restore it with podman load.
- Export a container's file system with podman export and know that it keeps no image history.
Questions by topic
- Private Registry Security4
- Backup Images and Container State6
- Image Tags and Push/Pull Operations16
- Private Registry Security and Multi-Registry Interaction5
- Inspect Running Applications1
- Understand Application Resource Descriptions1
Run Containers Locally Using Podman42 questions
This domain is day-to-day container work on one host. Candidates start containers, pass environment parameters, publish application ports, and read logs, events and inspect output.
Skills tested
- Start containers with podman run in detached or interactive mode, with a name and --rm when needed.
- Publish an application with -p and a host port:container port mapping.
- Pass environment parameters with the --env flag or an --env-file.
- Follow container logs with podman logs -f and watch the host with podman events.
- Read container settings with podman inspect and a --format Go template.
Questions by topic
- Container Execution and Lifecycle19
- Environment, Ports, and Application Management10
- Container Logs, Events, and Inspection2
- Inspect Running Applications1
- Container Volumes and Host Data Sharing2
- Expose Public Applications2
- Specify Environment Parameters2
- Use Podman Inspect1
- Security and Permissions for Host and Network Access3
Run Multi-Container Applications with Podman24 questions
Here one application spans several containers. Candidates create an application stack, order its dependencies, and give each container the environment variables, secrets, volumes and configuration it needs.
Skills tested
- Define an application stack in a compose YAML file and run it with podman-compose.
- Order service start-up with the depends_on directive.
- Store a database password with podman secret create instead of a plain environment variable.
- Share named volumes and bind-mounted config files between the services of a stack.
Questions by topic
- Create Application Stacks16
- Understand Container Dependencies4
- Working with Volumes in Multi-Container Apps3
- Inspect Running Applications for Issues1
Troubleshoot Containerized Applications15 questions
The last domain is about finding why an application fails. Candidates read resource descriptions, check application logs, inspect running applications and connect to a container to test from inside it.
Skills tested
- Read container and image metadata to find a wrong port, variable or mount.
- Check application logs with podman logs and in log files inside the container.
- Open a shell in a running container with podman exec and run diagnostic commands.
- Trace a container restart loop to its exit code and its last log lines.
Questions by topic
- Get Application Logs for Troubleshooting4
- Understand Application Resource Descriptions4
- Inspect Running Applications for Issues7
Requirements
- No formal prerequisites: anyone can book the exam.
- Recommended: the DO188 course from Red Hat, which teaches containers with Podman.
- Recommended: experience in a Linux terminal session and some shell scripting.
- Recommended: RHCSA, which helps but is not required.
About the EX188 exam
EX188 proves that a Linux administrator or developer can build container images, run containers and fix them with Podman. Red Hat runs it as a practical exam: candidates complete tasks on a live Red Hat Enterprise Linux system instead of choosing answers. The tasks cover Containerfiles, image registries, single containers, multi-container applications and troubleshooting. Passing earns the Red Hat Certified Specialist in Containers certification, which stays current for three years.
The PlanetCert practice test gives the most questions to Containerfile work and to running containers locally. Its explanations show why one choice works and a close one does not. For example, EXPOSE only records a port, while -p publishes it. Study Mode suits the Manage Images domain, where registries.conf, image tags and fully qualified names are easy to mix up. Brainy AI Assistant can explain how CMD and ENTRYPOINT combine, or turn a missed question into a short task to try in a terminal.
How to earn the certification
- Earns
- Red Hat Certified Specialist in ContainersSpecialist
The certification stays current for three years.
- Before
- EX200 Red Hat Certified System Administrator (RHCSA)
Recommended but not required. RHCSA proves the Linux administration skills that container work builds on.
- EX200 Red Hat Certified System Administrator (RHCSA)
- After
- EX280 Red Hat Certified OpenShift Administrator
The administrator path: running and managing containers at scale on Red Hat OpenShift.
- EX288 Red Hat Certified OpenShift Application Developer
The developer path: building and deploying applications on Red Hat OpenShift.
- EX280 Red Hat Certified OpenShift Administrator
How to prepare for EX188
- 1
Set up a RHEL 9 lab with Podman
Install Podman on a Red Hat Enterprise Linux 9 machine or virtual machine. Work as an ordinary user, because rootless containers behave differently from rootful ones.
- 2
Rebuild images one instruction at a time
Write Containerfiles for a web server and a small application. Change one instruction at a time, such as USER, ENV or ENTRYPOINT, rebuild, and check the effect with podman inspect.
- 3
Move images between registries
Log in to a registry such as Quay.io, tag an image with its fully qualified name, push it and pull it back. Then save the image to an archive and load it on a second host.
- 4
Run and break a small stack
Run a web front end and its database as one stack, with a secret, a named volume and a dependency. Break one setting on purpose and find it again from the logs.
- 5
Time the practice, repeat the misses
Take the EX188 practice test in Timed Mode once the labs feel routine. Repeat each missed task in a terminal, because the real exam is marked on working results.
Start a timed EX188run
Red Hat's recommended course is Red Hat OpenShift Development I: Introduction to Containers with Podman (DO188).
Who EX188 is for
- Linux system administrators who package and run services in containers.
- Developers who build and ship their applications as container images.
- RHCSA holders who want a container certification before they move on to OpenShift.
Typical job titles: Linux administrator · DevOps engineer · Container platform engineer · Application developer · Site reliability engineer
EX188 glossary
18 terms from the exam objectives and the vendor's official material, each defined in a sentence.
- :Z and :z volume options
- Volume mount options that relabel host files for SELinux: lowercase z shares the label between containers, and uppercase Z makes it private to one container.
- ADD instruction
- A Containerfile instruction that copies files like COPY, but can also unpack local tar archives and fetch files from a URL.
- ARG instruction
- A Containerfile instruction that defines a variable available only while the image is being built.
- Build context
- The directory sent to the build, whose files the COPY and ADD instructions can place in the image.
- CMD instruction
- The Containerfile instruction that sets the default command or arguments, which a user can override on the podman run command line.
- Containerfile
- A text file of build instructions that Podman reads, step by step, to produce a container image.
- COPY instruction
- A Containerfile instruction that copies files from the build context into the image.
- depends_on directive
- A compose file setting that makes one service start only after the services it depends on.
- ENTRYPOINT instruction
- The Containerfile instruction that sets the program a container always runs. CMD can then supply its default arguments.
- ENV instruction
- A Containerfile instruction that sets an environment variable that stays in the image and in every container started from it.
- FROM instruction
- The first Containerfile instruction, which names the base image that the new image starts from.
- Fully qualified image names
- Image names that include the registry, the repository and the tag, so Podman pulls exactly the intended image.
- Named volumes
- Storage that Podman creates and manages by name, which keeps its data when the container that used it is removed.
- podman export
- A command that writes a container's file system to a tar archive, without the image layers or history.
- podman save
- A command that writes an image, with its layers and metadata, to an archive file that podman load can restore.
- registries.conf
- The Podman configuration file that lists which registries to search for short image names and which registries are insecure.
- Rootless containers
- Containers that an ordinary user runs without root privileges on the host, which limits the damage a compromised container can do.
- Universal Base Image (UBI)
- A Red Hat base image built from Red Hat Enterprise Linux content that can be used to build and share container images.