mediumMultiple Select
XK0-006 Practice Question: Which TWO options are valid ways to pass…
Which TWO options are valid ways to pass environment variables to a Docker container?
⚠ Common exam trap
Many candidates confuse the `-v` flag (used for volumes) with environment variable flags, or assume `--var` or `--variable` are valid Docker options when they are not.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
--env-file file
The `--env-file` flag allows you to pass a file containing environment variables to a Docker container, where each line in the file is in `KEY=value` format. Option C is correct because the `-e` (or `--env`) flag directly sets an environment variable inside the container, e.g., `-e VAR=value`. Both are standard Docker CLI methods for injecting environment variables at container runtime.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
--var VAR=value
Why it's wrong here
Docker defines no --var flag; the documented options are -e, --env and --env-file. The abbreviation looks like a natural shorthand for variable, which explains its appeal, yet the CLI parses only the exact registered flag names and would error on --var.
- ✓
--env-file file
Why this is correct
The --env-file flag reads a file containing VAR=value lines and injects each as an environment variable in the container. It satisfies the stem's requirement for a valid way to pass environment variables, allowing bulk configuration without repeating -e flags.
- ✓
-e VAR=value
Why this is correct
The -e flag sets a single environment variable directly in the container at runtime, for example -e VAR=value. It satisfies the stem's requirement for a valid way to pass environment variables, injecting the value into the container's environment without a file.
- ✗
--variable VAR=value
Why it's wrong here
Docker has no --variable flag; environment variables are supplied with -e or --env, or via --env-file. The name resembles the real --env option, which is what makes it plausible, but Docker's CLI rejects --variable outright rather than mapping it to environment injection.
- ✗
-v VAR=value
Why it's wrong here
The -v flag mounts a host path or named volume into the container filesystem; it has no environment-variable syntax, so VAR=value is parsed as a volume specification. It is tempting because -v is a genuine, frequently used docker run flag, but for environment variables the correct flags are -e or --env.
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Related to this question
Learn chapter
Managing Storage and File Systems
Key term
Value
Value is the perceived worth, benefit, or usefulness that a service, product, or activity delivers to stakeholders, especially customers and the business.
Key term
CLI
A CLI (command-line interface) is a text-based way to interact with a computer's operating system by typing commands instead of clicking icons.
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