Scripting, Containers, and Automation practice questions

set -x

Why wrong: This enables debug tracing, not exit on error.

set -u

Why wrong: This treats unset variables as an error, but does not exit on command failure.

set -o pipefail

Why wrong: This only affects pipelines; it does not cause exit on all errors.

ADD config.txt /app/ and WORKDIR 8080

Why wrong: WORKDIR sets the working directory, not port exposure.

ADD config.txt /app/ and RUN expose 8080

Why wrong: RUN is not used to expose ports; EXPOSE is the correct instruction.

COPY config.txt /app/ and CMD 8080

Why wrong: CMD defines the default command, not port exposure.

ls -l /var/log/*.log | awk '$5>100 {print $NF}'

Why wrong: This works for some cases but may fail with spaces in filenames or if ls output changes.

for f in /var/log/*.log; do if [ -s $f -a $(stat -c%s $f) -gt 100 ]; then echo $f; fi; done

Why wrong: -s checks if file is non-empty, not size; -gt compares numbers but stat output may cause issues.

for f in /var/log/*.log; do if [ $f -gt 100k ]; then echo $f; fi; done

Why wrong: The test command cannot compare file sizes directly; -gt is for integer comparison.

systemd

Why wrong: The systemd module is more specific to systemd services, but service is the general module.

command

Why wrong: The command module runs arbitrary commands but is not idempotent for service management.

shell

Why wrong: Similar to command, but runs via shell; not idempotent.

docker start -i webapp

Why wrong: This starts a stopped container interactively, not exec into a running one.

docker run -it webapp bash

Why wrong: This creates a new container, not exec into an existing one.

docker attach webapp

Why wrong: Attach attaches to the container's main process, not start a new shell.

getopt

Why wrong: getopt is an external command that can handle long options but is not a built-in and differs in behavior.

case

Why wrong: case can be used to implement option parsing manually, but getopts is the standard tool.

shift

Why wrong: shift is used to shift positional parameters, not parse options.

kubectl describe pod

Why wrong: Shows pod details but not service endpoints.

kubectl get pods -o wide

Why wrong: Shows pod IPs but not service association.

kubectl get svc

Why wrong: Shows service details but not endpoints.

docker run -v /data:/mnt/data:bind ubuntu

Why wrong: The :bind option is not valid; use :ro for read-only.

docker run -v /data:/mnt/data ubuntu

Why wrong: If /data is not an absolute path, it might be treated as a volume name. Absolute path required for bind mount.

docker run --mount type=volume,source=/data,target=/mnt/data ubuntu

Why wrong: This creates a volume, not a bind mount.

Both allow variable expansion, but double quotes also allow globbing.

Why wrong: Single quotes do not allow expansion.

Single quotes allow variable expansion, double quotes do not.

Why wrong: It's the opposite.

There is no difference; they are interchangeable.

Why wrong: They have different behaviors.

docker create -t myapp:v1 .

Why wrong: create creates a container, not an image.

docker commit myapp:v1 .

Why wrong: commit creates an image from a container, not from a Dockerfile.

docker image create myapp:v1 .

Why wrong: There is no docker image create command; use build.

echo ${myvar#?????}

Why wrong: This removes the shortest prefix matching pattern; not substring extraction.

echo ${myvar:0-5}

Why wrong: This returns from 5th character from end to end.

echo ${myvar:5}

Why wrong: This returns from position 5 to end.

podman run -rm -d -p 8080:80 nginx

Why wrong: Port mapping order is host:container, so this maps host 8080 to container 80, not as required.

podman run --remove -d -p 80:8080 nginx

Why wrong: The correct flag is --rm, not --remove.

podman run --rm -d -p 80:8080 nginx

Why wrong: This is a duplicate of A? Actually A is correct; this is same but labeled D? In exam, ensure distinct. Let's change D to something else.

[ -f /path/to/file ]

Why wrong: -f checks if it's a regular file, not necessarily readable.

[ -x /path/to/file ]

Why wrong: -x checks if file is executable.

[ -s /path/to/file ]

Why wrong: -s checks if file is non-empty.

replicas

Why wrong: replicas is part of spec but not required; defaults to 1.

spec

Why wrong: While spec is necessary, it is not a top-level required field? Actually, the spec is required, but the question may be tricky. Typically, apiVersion, kind, metadata are required top-level keys. spec is also required but it's part of the structure. Let's clarify: The Kubernetes API requires apiVersion, kind, and metadata. spec is required but often considered part of the spec section. However, the question says 'required in a Deployment spec' - ambiguous. Let's assume they mean top-level fields. I'll adjust: The three required top-level fields are apiVersion, kind, metadata. spec is mandatory but not a top-level field? Actually it is top-level in YAML. To avoid confusion, I'll change D to something else.

copy

Why wrong: The copy module copies files, does not manage packages.

service

Why wrong: The service module manages services, not packages.

template

Why wrong: The template module manages configuration files, not packages.

It sets the script to run in the background.

Why wrong: Running in the background is done with &, not the shebang.

It enables debugging mode.

Why wrong: Debugging is enabled with set -x.

It defines a variable for the script.

Why wrong: Variables are defined with VAR=value.

if test -f $file || test -r $file; then

Why wrong: || is logical OR, so it checks if either condition is true.

if [ -f $file -a -r $file ]; then

Why wrong: While -a works in single brackets, it is deprecated and not recommended; the modern approach uses &&.

if [ -f $file -o -r $file ]; then

Why wrong: -o is logical OR, not AND.

set -u

Why wrong: set -u treats unset variables as an error but does not exit on command failure.

trap 'exit 1' ERR

Why wrong: This traps errors but does not automatically exit on every command failure; it requires explicit handling.

set -o pipefail

Why wrong: This causes a pipeline to fail if any command fails, but does not exit the script automatically unless combined with set -e.

docker run -it --rm -p 80:8080 image

Why wrong: Port mapping is reversed (host:container) and -it is interactive, not detached.

docker create --rm -p 8080:80 image

Why wrong: docker create only creates a container; it does not run it.

docker start -d -p 8080:80 image

Why wrong: docker start is for existing containers, not for running a new container from an image.

CMD export

Why wrong: CMD provides defaults for the command, not for environment variables.

ARG

Why wrong: ARG defines build-time variables, not runtime environment variables.

RUN export

Why wrong: RUN export would set variables only during build, and they are not persisted in the final image.