Mounting read-only volumes in Docker - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does mounting a volume as read-only mean in Docker?

It means the container can read files from the volume but cannot change or write new files to it.

beginner

How do you specify a read-only volume mount in a Docker run command?

Add :ro at the end of the volume mount path, for example: docker run -v /host/path:/container/path:ro.

beginner

Why would you want to mount a volume as read-only?

To protect the data from accidental changes or deletion by the container, ensuring data safety.

beginner

Can a container write to a read-only mounted volume?

No, the container cannot write or modify files in a volume mounted as read-only.

intermediate

What happens if a container tries to write to a read-only volume?

The write operation will fail, usually with a permission denied error.

How do you mount a volume as read-only in Docker?

A Add ':ro' at the end of the volume path

B Add ':rw' at the end of the volume path

C Use '--read-only' flag in docker run

D Mount the volume without any suffix

To mount a volume as read-only, you add ':ro' after the volume path in the docker run command.

What is the effect of mounting a volume as read-only?

A Container can only write files

B Container can only read files, not write

C Container cannot access the volume

D Container can read and write files

Read-only means the container can read files but cannot write or modify them.

Which of these commands mounts a volume as read-only?

A docker run -v /data:/app/data myimage

B docker run -v /data:/app/data:rw myimage

C docker run -v /data:/app/data:ro myimage

D docker run --read-only -v /data:/app/data myimage

The ':ro' suffix makes the volume read-only.

What error might you see if a container tries to write to a read-only volume?

A Permission denied

B File not found

C Disk full

D Network timeout

Writing to a read-only volume results in a permission denied error.

Why is mounting volumes as read-only useful?

A To increase container memory

B To speed up container startup

C To allow container to write logs

D To prevent accidental data changes

Read-only mounts protect data by preventing changes from inside the container.

Explain how to mount a volume as read-only in Docker and why you might want to do this.

Think about how to stop a container from changing files on your host.

Describe what happens if a container tries to write to a volume mounted as read-only.

Consider file system permissions inside the container.