Midori-Obsidian/Midori's Linux Dojo 🌸/Phase 1 - Walking/Exercises.md

🪴 Phase 1: Walking

Goal: Get comfortable with the Linux command line

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🎯 Exercise 1 — Your First Commands

SSH into alpine-1 (through hop):

# Who am I?
whoami                  # → root
hostname                # → localhost (or your hostname)
uname -a                # Show full system info
uptime                  # How long since boot

# Where am I?
pwd                     # Print working directory
ls -la /                # List root directory contents

# Make a file
echo "Hello from Phase 1!" > /root/hello.txt
ls -l /root/hello.txt   # Check file details
cat /root/hello.txt      # Read the file

Repeat on alpine-2 too!

✅ Verified by Midori

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🎯 Exercise 2 — Navigation & File Basics

# Explore directories
ls /
ls /etc
ls /var
ls /home

# Create a directory structure
mkdir -p /root/lab/{notes,scripts,logs}
ls -R /root/lab

# Copy and move files
cp /root/hello.txt /root/lab/notes/
mv /root/hello.txt /root/lab/backup.txt

# Read system files
cat /etc/hostname
cat /etc/os-release
cat /etc/passwd

# Answer these:
echo $SHELL             # What shell am I using?
wc -l /etc/passwd       # How many users?
uname -r                # Kernel version

📝 Questions to answer:

1. What is your shell?
2. How many users are listed in /etc/passwd?
3. What kernel version are you running?

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🎯 Exercise 3 — File Permissions

# Step 1 — Check current permissions
ls -la /root/lab/

# Step 2 — Understand the columns
# -rw-r--r--  1  root  root  20  May 21  file
# ─┬─ ─┬─ ─── permissions, owner, group, size, date, name
#  │   └── user/group/other  (r=read, w=write, x=execute)
#  └── file type (-=file, d=directory)

# Step 3 — Create a script
# ⚠️ Alpine uses ash, NOT bash! Use #!/bin/sh
mkdir -p /root/lab/scripts
echo '#!/bin/sh' > /root/lab/scripts/sayhello.sh
echo 'echo "Hello from a script!"' >> /root/lab/scripts/sayhello.sh
# 🔴 If you use #!/bin/bash it will say "not found"!

# Step 4 — Check permissions before making it executable
ls -la /root/lab/scripts/sayhello.sh
# Try to run it — should fail (no +x)
./root/lab/scripts/sayhello.sh || echo "Failed! Need +x permission"

# Step 5 — Add execute permission
chmod +x /root/lab/scripts/sayhello.sh
ls -la /root/lab/scripts/sayhello.sh
./root/lab/scripts/sayhello.sh

# Step 6 — Change permissions with numeric mode
chmod 644 /root/lab/scripts/sayhello.sh
ls -la /root/lab/scripts/sayhello.sh

# Step 7 — Remove execute permission
chmod -x /root/lab/scripts/sayhello.sh
./root/lab/scripts/sayhello.sh || echo "Permission denied!"

# Step 8 — Work with directories (need +x to enter)
mkdir -p /root/lab/secret
echo "classified" > /root/lab/secret/data.txt
chmod 700 /root/lab/secret
ls -la /root/lab/ | grep secret
ls /root/lab/secret

📝 Questions:

1. What does ls -la show? Describe each column.
2. What does +x, -x, 644, 755, 700 mean?
3. Why does a script need +x but cat file.txt doesn't?
4. Why does a directory need +x to be accessible?

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🎯 Exercise 4 — Text Editors

# Try nano (easier)
nano /root/lab/notes/my-notes.txt
# Type some text, Ctrl+O to save, Ctrl+X to exit

# Try vi (classic)
vi /root/lab/notes/vi-practice.txt
# Press 'i' to insert, type something
# Press Esc, then ':wq' to save and quit

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💡 Key Lesson: Root bypasses everything!

• root can read/write/execute ANY file regardless of permissions
• Permissions only protect against non-root users
• Always use a regular user + sudo in production!
• Directories need +x to be accessible

🔢 Permission Cheat Sheet

Mode	Octal	Meaning
rwx------	700	Only owner can do anything
rwxr-xr-x	755	Owner full, others read+execute
rw-r--r--	644	Readable by all, writable by owner
rw-------	600	Only owner can read/write
rw-rw-rw-	666	Everyone can read/write (dangerous!)

✅ Phase 1 Complete Checklist

• Exercise 1: whoami, uname -a, file creation
• Exercise 2: Directory structure, cp, mv, cat
• Exercise 3: chmod, permissions understanding
• ⏭️ Exercise 4: Skipped (already know text editors)

Next: Phase 2 - Networking 🌐