[Solved] Consider this command:docker run --read-only -v /data alpine sh -c "echo hello > /data/file.txt && cat /data/file.txt"What will be the output? | Docker

Docker - Security

Consider this command:
docker run --read-only -v /data alpine sh -c "echo hello > /data/file.txt && cat /data/file.txt"
What will be the output?

Ahello

BPermission denied error

CNo such file or directory error

DEmpty output

Step-by-Step Solution

Solution:

Step 1: Understand --read-only with volume mount
The container filesystem is read-only, but the /data directory is mounted as a volume, which is writable.
Step 2: Analyze the command behavior
The command writes "hello" to /data/file.txt and then reads it back. Since /data is writable, this succeeds and outputs "hello".
Final Answer:
hello -> Option A
Quick Check:
Writable volume inside read-only container = writable [OK]

Quick Trick: Writable volumes override read-only container filesystem [OK]

Common Mistakes:

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