DOCKR CERTIFIED ASSOSIATE COMPREHENSIVE
EXAM 2026 |||QUESTIONS AND ANSWERS WITH
RATIONALES/GRADED A+/2026 UPDATE/100%
CORRECT
Q1. Swarm Mode True/False
Question: Which of the following is NOT true regarding Docker Swarm Mode?
A. You can deploy both managers and workers using the Docker Engine
B. For each service, you can declare the number of tasks you want to run, and the
swarm manager automatically adapts
C. The swarm manager automatically assigns addresses to containers on overlay
networks
D. Docker Swarm Mode is a plugin which you can install alongside Docker
Answer: D
Rationale: Docker Swarm Mode is built into the Docker Engine (since version
1.12). It is not a separate plugin or add-on.
Q2. Swarm Quorum Calculation
Question: A Docker Swarm cluster has 5 manager nodes. How many manager
nodes can fail simultaneously while the cluster remains operational?
A. 1
B. 2
C. 3
D. 5
Answer: B
,Rationale: Swarm uses the Raft consensus algorithm requiring a majority
(quorum) of managers. With 5 managers, the quorum is 3 (majority of 5), so the
cluster tolerates 5 - 3 = 2 failures. Formula: fault tolerance = (N - 1) / 2 for N
manager nodes.
Q3. Global vs. Replicated Services
Question: You have 3 nodes. Only 2 should run a high-memory web service, but
every node must run a monitoring service. Which configuration is correct?
A. Replicated service for web, Global service for monitoring
B. Global service for web, Replicated service for monitoring
C. Replicated service for both
D. Global service for both
Answer: A
Rationale: Global services run one task on every node. Replicated services allow
you to specify the exact number of replicas and which nodes they run on (using
placement constraints).
Q4. Updating Swarm Secrets
Question: Bob wants to update the secret being used by one of his services. What
is the correct sequence?
A. Update the existing secret using docker secret update
B. Update the existing secret, restart all services using this secret
C. Create a new secret, update the service to use this new secret, delete the old
secret
D. Create a new secret, create a new service with this new secret, delete old
secret and service
Answer: C
,Rationale: Secrets in Docker Swarm are immutable for security. You cannot edit
an existing secret. The correct workflow is: create a new secret → update the
service to use it (rolling update) → remove the old secret.
Domain 2: Image Creation, Management, and Registry (20% of exam)
Master Dockerfiles, multi-stage builds, and registry operations.
Q5. Multi-stage Builds
Question: Which statement is NOT TRUE about multi-stage builds?
A. Multi-stage builds eliminate the need for separate Dockerfiles
B. Multi-stage builds help create smaller image sizes
C. You cannot select which step to start your build process once you've defined all
steps
D. With multi-stage builds, you can create images for different purposes (dev and
production)
Answer: C
Rationale: You can select a specific stage using docker build --target
<stage_name>. This allows you to stop at a particular stage for debugging or build
only the production stage.
Q6. Image Size Optimization
Question: A developer has a Dockerfile that produces a 1.2 GB image. The
application is a compiled Go binary that only needs the binary to run. How can the
image size be reduced to under 20 MB?
A. docker image prune
B. Multi-stage build using scratch
C. Compress the image with docker save
D. Use the --squash flag during build
, Answer: B
Rationale: Multi-stage builds allow compilation in a large "builder" image and
then copying only the final binary to a minimal base like scratch (empty)
or alpine (~5MB). This removes all build dependencies from the final image.
Q7. Custom Dockerfile Name
Question: You are in a directory containing a file named Dockerfile-app. You want
to build an image using this file without renaming it to Dockerfile. Which
command is correct?
A. docker build -d Dockerfile-app
B. docker build -f Dockerfile-app
C. docker build --dockerfile Dockerfile-app
D. docker build --from-file Dockerfile-app
Answer: B
Rationale: The -f (or --file) flag specifies the name of the Dockerfile to use when it
is not named Dockerfile.
Q8. Image Layers
Question: Select the two correct statements about images and containers.
A. An image is a collection of immutable layers; a container is a running instance
of an image
B. A container can exist without an image, but an image cannot exist without a
container
C. Only one container can be spawned from a given image at a time
D. If multiple containers are spawned from the same image, they all use the same
copy of the image in memory
Answer: A and D
EXAM 2026 |||QUESTIONS AND ANSWERS WITH
RATIONALES/GRADED A+/2026 UPDATE/100%
CORRECT
Q1. Swarm Mode True/False
Question: Which of the following is NOT true regarding Docker Swarm Mode?
A. You can deploy both managers and workers using the Docker Engine
B. For each service, you can declare the number of tasks you want to run, and the
swarm manager automatically adapts
C. The swarm manager automatically assigns addresses to containers on overlay
networks
D. Docker Swarm Mode is a plugin which you can install alongside Docker
Answer: D
Rationale: Docker Swarm Mode is built into the Docker Engine (since version
1.12). It is not a separate plugin or add-on.
Q2. Swarm Quorum Calculation
Question: A Docker Swarm cluster has 5 manager nodes. How many manager
nodes can fail simultaneously while the cluster remains operational?
A. 1
B. 2
C. 3
D. 5
Answer: B
,Rationale: Swarm uses the Raft consensus algorithm requiring a majority
(quorum) of managers. With 5 managers, the quorum is 3 (majority of 5), so the
cluster tolerates 5 - 3 = 2 failures. Formula: fault tolerance = (N - 1) / 2 for N
manager nodes.
Q3. Global vs. Replicated Services
Question: You have 3 nodes. Only 2 should run a high-memory web service, but
every node must run a monitoring service. Which configuration is correct?
A. Replicated service for web, Global service for monitoring
B. Global service for web, Replicated service for monitoring
C. Replicated service for both
D. Global service for both
Answer: A
Rationale: Global services run one task on every node. Replicated services allow
you to specify the exact number of replicas and which nodes they run on (using
placement constraints).
Q4. Updating Swarm Secrets
Question: Bob wants to update the secret being used by one of his services. What
is the correct sequence?
A. Update the existing secret using docker secret update
B. Update the existing secret, restart all services using this secret
C. Create a new secret, update the service to use this new secret, delete the old
secret
D. Create a new secret, create a new service with this new secret, delete old
secret and service
Answer: C
,Rationale: Secrets in Docker Swarm are immutable for security. You cannot edit
an existing secret. The correct workflow is: create a new secret → update the
service to use it (rolling update) → remove the old secret.
Domain 2: Image Creation, Management, and Registry (20% of exam)
Master Dockerfiles, multi-stage builds, and registry operations.
Q5. Multi-stage Builds
Question: Which statement is NOT TRUE about multi-stage builds?
A. Multi-stage builds eliminate the need for separate Dockerfiles
B. Multi-stage builds help create smaller image sizes
C. You cannot select which step to start your build process once you've defined all
steps
D. With multi-stage builds, you can create images for different purposes (dev and
production)
Answer: C
Rationale: You can select a specific stage using docker build --target
<stage_name>. This allows you to stop at a particular stage for debugging or build
only the production stage.
Q6. Image Size Optimization
Question: A developer has a Dockerfile that produces a 1.2 GB image. The
application is a compiled Go binary that only needs the binary to run. How can the
image size be reduced to under 20 MB?
A. docker image prune
B. Multi-stage build using scratch
C. Compress the image with docker save
D. Use the --squash flag during build
, Answer: B
Rationale: Multi-stage builds allow compilation in a large "builder" image and
then copying only the final binary to a minimal base like scratch (empty)
or alpine (~5MB). This removes all build dependencies from the final image.
Q7. Custom Dockerfile Name
Question: You are in a directory containing a file named Dockerfile-app. You want
to build an image using this file without renaming it to Dockerfile. Which
command is correct?
A. docker build -d Dockerfile-app
B. docker build -f Dockerfile-app
C. docker build --dockerfile Dockerfile-app
D. docker build --from-file Dockerfile-app
Answer: B
Rationale: The -f (or --file) flag specifies the name of the Dockerfile to use when it
is not named Dockerfile.
Q8. Image Layers
Question: Select the two correct statements about images and containers.
A. An image is a collection of immutable layers; a container is a running instance
of an image
B. A container can exist without an image, but an image cannot exist without a
container
C. Only one container can be spawned from a given image at a time
D. If multiple containers are spawned from the same image, they all use the same
copy of the image in memory
Answer: A and D
