View source for DWTutorials:Linux Basics for Beginners/Answer Key

{{DISPLAYTITLE:DWTutorials Linux Basics — Instructor Answer Key}}
__NOTOC__

= Instructor Answer Key =

'''For DWShells staff and course mentors'''

This page supports the student course [[Linux Basics for Beginners]]. Protect it if you do not want learners to see suggested answers before completing their work.

'''Copyright:''' © 2026 DarkWorld Network. All rights reserved.

== Assessment model ==

{| class="wikitable"
|-
! Component
! Weight
! Evidence
|-
| Lesson review questions
| 30%
| Accurate explanations in the learner's own words
|-
| Hands-on labs
| 40%
| Correct files, command output, permissions, and safe working habits
|-
| Final project
| 30%
| Script, report, documentation, permissions, archive, and restore test
|}

Suggested pass mark: '''70%'''. Safety violations should be corrected before the learner passes, even if the numeric score is high.

Accept equivalent commands when they are safe and produce the required outcome. Do not require output to match usernames, paths, dates, process IDs, hostnames, package versions, or file sizes shown in the course.

----

= Lesson 1 answers =

# A '''terminal''' is the interface/application used to enter commands; a '''shell''' is the program that interprets those commands.
# SSH (Secure Shell).
# Linux deliberately does not echo password characters, reducing information visible to someone watching.
# <code>pwd</code>.
# Ctrl+C.

'''Lab check:''' Learner can connect, identify the current user and host, print the requested sentence, recall history with the Up arrow, log out with <code>exit</code>, and reconnect.

= Lesson 2 answers =

# <code>/</code> is the top of the filesystem; <code>/root</code> is normally the root administrator's home directory.
# The current user's home directory.
# <code>-a</code>.
# Absolute, because it begins with <code>/</code>.
# <code>.</code> is the current directory; <code>..</code> is its parent.

'''Lab check:''' Ask the learner to move to <code>/etc</code>, report <code>pwd</code>, return home, and explain why <code>cd -</code> may produce a different location than <code>cd ..</code>.

= Lesson 3 answers =

# <code>mkdir -p</code>.
# <code>cp -r SOURCE DESTINATION</code>.
# <code>mv</code>.
# It asks before removal and helps prevent an accidental deletion.
# Non-hidden names ending in <code>.txt</code> in the selected directory.

'''Expected lab structure:'''

<pre>
lesson-03/
├── activity.log
├── one.txt
└── practice/
    ├── archive/
    │   └── activity.log
    ├── one.txt
    └── two.txt
</pre>

The top-level <code>two.txt</code> should have been removed. Extra files from earlier examples are acceptable.

= Lesson 4 answers =

# <code>less</code> is better for long content because it supports paging and searching.
# <code>q</code>.
# Ctrl+O.
# <code>head</code> displays the beginning; <code>tail</code> displays the end.
# The compared files are identical.

'''Lab check:''' <code>profile.txt</code> contains the requested content. The learner can save and exit Nano, select first/last lines, count lines, and explain the <code>diff -u</code> result.

= Lesson 5 answers =

# <code>--help</code>.
# <code>man COMMAND</code>.
# <code>q</code>.
# Whether a command exists and what executable, builtin, function, or alias the shell will use.
# They may be saved in history and exposed later.

'''Lab check:''' The learner identifies <code>mkdir -p</code>, understands that <code>cd</code> is a shell builtin, and uses <code>history | tail -n 10</code> or an equivalent safe command.

= Lesson 6 answers =

# Owner, group, and others.
# 5: read (4) plus execute (1).
# It permits traversal/entry and access to known names, subject to other directory permissions.
# <code>chmod</code>.
# It grants read, write, and execute permissions to everyone, allowing unauthorized modification.

'''Expected permissions:'''

<pre>-rw------- private.txt
-rw-r----- shared.txt
drwx------ private-dir</pre>

The learner should demonstrate the difference between <code>ls -l</code> and <code>ls -ld</code> for a directory.

= Lesson 7 answers =

# <code>></code> replaces/truncates; <code>>></code> appends.
# 2.
# It connects one command's standard output to the next command's standard input.
# <code>uniq</code> normally recognizes only adjacent duplicates, so sorting brings equal lines together.
# Success.

'''Lab check:''' The learner can use <code>grep -i</code>, <code>wc -l</code>, <code>sort</code>, <code>>></code>, <code>2></code>, and <code>tee</code>, and can explain where normal and error output went.

= Lesson 8 answers =

# To avoid slow, resource-intensive traversal and irrelevant permission errors.
# <code>-i</code> ignores case; <code>-v</code> inverts the match.
# No.
# To preserve the entire value as one argument and prevent wildcard expansion or word splitting.
# It runs <code>date +%F</code> and substitutes its YYYY-MM-DD output.

'''Lab check:''' The learner creates and accesses a filename containing a space without accidental splitting, and uses a quoted variable correctly.

= Lesson 9 answers =

# Process ID.
# <code>jobs</code> shows jobs associated with the current shell; <code>ps</code> queries system processes according to its options.
# SIGTERM.
# It prevents the process from cleaning up files, locks, and state.
# The server is shared, resource limits protect everyone, and technical availability is not authorization.

'''Lab check:''' No practice <code>sleep</code> process should remain. The learner must verify ownership and PID before sending a signal.

= Lesson 10 answers =

# <code>/etc/os-release</code>.
# <code>df</code> reports filesystem capacity; <code>du</code> estimates space used by files/directories.
# ICMP may be filtered even while the destination and other services are available.
# <code>-t</code>.
# Uppercase <code>-P</code>.

'''Lab check:''' The archive lists and extracts successfully into a separate directory. The original data remains unchanged. If SCP cannot be tested, the learner should still explain local and remote sides correctly.

= Lesson 11 answers =

# The first line that selects the script interpreter, such as <code>#!/bin/bash</code>.
# The current directory is not normally searched through <code>PATH</code>; <code>./</code> names the path explicitly.
# <code>$0</code> is the script name and <code>$1</code> is the first argument.
# 0.
# To preserve spaces and prevent unintended splitting or wildcard expansion.

'''Lab check:''' <code>course-summary.sh</code> passes <code>bash -n</code>, rejects a missing name with a non-zero exit status, writes the required fields, and sets the output to <code>600</code>.

= Lesson 12 answers =

# The private key stays on the learner's local device and is never shared. Only the public key is installed on the server or sent to authorized staff.
# <code>700</code> for <code>~/.ssh</code> and <code>600</code> for <code>authorized_keys</code>.
# The downloaded content runs before the learner has inspected or verified it.
# No. Technical access is not authorization.
# Stop and ask DWShells staff before proceeding.

'''Lab check:''' The learner can explain host-key checking, password/key privacy, safe permissions, shared-resource responsibility, and why policy applies even to technically possible actions.

----

= Final project reference implementation =

This is one valid implementation of <code>bin/learner-report.sh</code>. Learners may organize their code differently.

<syntaxhighlight lang="bash">
#!/bin/bash

set -u
umask 077

if [ "$#" -ne 1 ]; then
    echo "Usage: $0 DISPLAY_NAME" >&2
    exit 1
fi

display_name="$1"
script_dir="$(cd -- "$(dirname -- "$0")" && pwd)"
project_dir="$(dirname -- "$script_dir")"
output_dir="$project_dir/output"
output="$output_dir/learner-report.txt"

mkdir -p "$output_dir"

if [ -r /etc/os-release ]; then
    debian_version="$(. /etc/os-release; printf '%s' "$PRETTY_NAME")"
else
    debian_version="Unknown"
fi

{
    echo "DWShells Linux learner report"
    echo "Learner: $display_name"
    echo "Username: $USER"
    echo "Hostname: $(hostname)"
    echo "Generated: $(date --iso-8601=seconds)"
    echo "Debian: $debian_version"
    echo "Kernel: $(uname -r)"
    echo "Architecture: $(uname -m)"
    echo "Home: $HOME"
    echo
    echo "Linux course usage:"
    du -sh "$HOME/linux-course"
    echo
    echo "Home filesystem:"
    df -h "$HOME"
} > "$output"

chmod 600 "$output"
echo "Report written to $output"
exit 0
</syntaxhighlight>

Suggested checks:

<syntaxhighlight lang="bash">
cd "$HOME/linux-course/linux-final"
bash -n bin/learner-report.sh
bin/learner-report.sh
echo "$?"
bin/learner-report.sh "Test Learner"
echo "$?"
stat -c '%a %n' bin/learner-report.sh output/learner-report.txt
cat output/learner-report.txt
</syntaxhighlight>

Expected permissions are <code>700</code> for the script and <code>600</code> for the report. A missing name should produce a non-zero status; a successful run should produce status zero.

== Final project rubric ==

{| class="wikitable" style="width:100%;"
|-
! Area
! Points
! Full-credit standard
|-
| Required directory structure
| 3
| All required directories and files exist in the correct locations.
|-
| README
| 3
| Clearly explains purpose, requirements, command syntax, and output.
|-
| Command notes
| 3
| Ten correct commands with clear one-line explanations.
|-
| Argument validation
| 3
| Missing display name produces usage on stderr and exits non-zero.
|-
| Report content
| 6
| All nine required fields are present and accurate.
|-
| Quoting and safe paths
| 3
| Variables are quoted; script works regardless of the caller's current directory.
|-
| Permissions
| 2
| Script is 700 and report is 600.
|-
| Syntax and repeatability
| 2
| Passes <code>bash -n</code> and runs twice without unsafe side effects.
|-
| Archive and restore
| 3
| Archive lists correctly and restores all files into a separate test location.
|-
| Security and policy
| 2
| No secrets, privilege escalation, broad searches, destructive operations, or prohibited activity.
|-
! Total
! 30
! Suggested pass for this component: 21/30
|}

== Common deductions and coaching ==

{| class="wikitable"
|-
! Issue
! Coaching response
|-
| Learner typed the example <code>$</code> prompt.
| Re-explain prompt versus command; have them retry.
|-
| Paths or variables are unquoted.
| Test with a display name or path containing a space and explain word splitting.
|-
| Learner used <code>chmod 777</code>.
| Ask which identities need each permission, then choose the minimum required mode.
|-
| Learner used SIGKILL first.
| Practise SIGTERM, wait, recheck, and reserve SIGKILL for a verified last resort.
|-
| Learner searched from <code>/</code>.
| Stop the command and narrow the starting path to <code>$HOME</code> or the project.
|-
| Learner copied a command without understanding it.
| Ask them to explain every program, option, argument, redirection, and expansion before rerunning.
|-
| Report exposes secrets.
| Remove the data, rotate any exposed credential, correct the script, and explain secure secret handling.
|}

== Pre-publication staff checklist ==

Before each course intake:

# Confirm the current SSH hostname and port.
# Publish or provide the current SSH host-key fingerprint through a trusted channel.
# Confirm which account home layouts are active, such as <code>/home/free/USER</code> and <code>/home/support/USER</code>.
# Test command availability: <code>bash</code>, <code>nano</code>, <code>man</code>, <code>less</code>, <code>find</code>, <code>grep</code>, <code>tar</code>, <code>getent</code>, <code>curl</code>, <code>ping</code>, <code>quota</code>, and <code>stat</code>.
# Mark unavailable optional commands in the student page.
# Link the current DWShells Acceptable Use Policy and support channel.
# Verify storage, process, CPU, memory, and network limits.
# Test every lab using an ordinary free account and an ordinary support account—not root.
# Confirm that home-directory permissions prevent cross-user data exposure.
# Confirm that the answer-key page is protected as intended.

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''DWTutorials Linux Basics Instructor Answer Key — © 2026 DarkWorld Network. All rights reserved.''

[[Category:DWShells]]
[[Category:Linux course administration]]