Backup and recovery strategies in Raspberry Pi - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the output of this Raspberry Pi backup script snippet?

Consider this Python script running on a Raspberry Pi to create a backup of a directory. What will be printed after execution?

Raspberry Pi

import os
backup_dir = '/home/pi/backup'
source_dir = '/home/pi/data'
os.system(f'mkdir -p {backup_dir}')
os.system(f'cp -r {source_dir}/* {backup_dir}/')
print('Backup completed')

A SyntaxError

B Backup completed

C FileNotFoundError

D Permission denied

💡 Hint

The script creates the backup directory if it doesn't exist and copies files.

The script uses os.system to create the backup directory and copy files. If the directories exist and permissions are correct, it prints 'Backup completed'.

❓ Predict Output

intermediate

What error does this recovery script raise?

This Python snippet attempts to restore files from a backup folder on a Raspberry Pi. What error will it raise if the backup folder does not exist?

Raspberry Pi

import shutil
backup_dir = '/home/pi/backup'
restore_dir = '/home/pi/data'
shutil.copytree(backup_dir, restore_dir)

A FileNotFoundError

B PermissionError

C KeyError

D SyntaxError

💡 Hint

copytree requires the source directory to exist.

If the source directory does not exist, shutil.copytree raises FileNotFoundError.

🧠 Conceptual

advanced

Which backup strategy minimizes data loss on a Raspberry Pi?

You want to back up your Raspberry Pi data regularly. Which strategy best minimizes data loss if the Pi crashes unexpectedly?

A Full backup once a month

B Differential backup once a week

C Incremental backup every hour

D No backup, just copy files manually

💡 Hint

Think about how often data changes and how quickly you want to recover.

Incremental backups every hour save only changes since the last backup, minimizing data loss and storage use.

❓ Predict Output

advanced

What is the output of this Raspberry Pi backup verification script?

This Python script checks if the backup directory contains the expected number of files. What will it print if the backup has exactly 5 files?

Raspberry Pi

import os
backup_dir = '/home/pi/backup'
files = os.listdir(backup_dir)
if len(files) == 5:
    print('Backup verified')
else:
    print('Backup incomplete')

A PermissionError

B Backup incomplete

C FileNotFoundError

D Backup verified

💡 Hint

The script counts files and compares to 5.

If the backup directory has exactly 5 files, the script prints 'Backup verified'.

❓ Predict Output

expert

What is the value of variable 'status' after running this Raspberry Pi backup script?

This Python script attempts to back up a directory and sets 'status' based on success. What is the value of 'status' after running?

Raspberry Pi

import subprocess
backup_dir = '/home/pi/backup'
source_dir = '/home/pi/data'
try:
    subprocess.run(['cp', '-r', source_dir + '/*', backup_dir], check=True)
    status = 'Success'
except subprocess.CalledProcessError:
    status = 'Failed'

A Failed

B Success

C SyntaxError

D FileNotFoundError

💡 Hint

Check how subprocess.run handles shell wildcards without shell=True.

The wildcard '*' is not expanded without shell=True, so the command fails and status is set to 'Failed'.

Practice

1. What is the main purpose of creating backups on a Raspberry Pi?

easy

A. To install new software automatically

B. To speed up the Raspberry Pi's processing power

C. To save copies of important files in case of data loss

D. To increase the screen resolution

Solution

1. Step 1: Understand the concept of backup

   Backups are copies of important data saved separately to prevent loss.

2. Step 2: Identify the main purpose on Raspberry Pi

   On Raspberry Pi, backups protect files from accidental deletion or corruption.

3. Final Answer:

   To save copies of important files in case of data loss -> Option C

4. Quick Check:

   Backup = Save copies [OK]

Hint: Backups protect data by saving copies elsewhere [OK]

Common Mistakes:

• Confusing backup with speeding up the device
• Thinking backup installs software
• Assuming backup changes display settings

2. Which command is commonly used on Raspberry Pi to create a full image backup of the SD card?

easy

A. rsync

B. dd

C. cp

D. mv

Solution

1. Step 1: Identify commands for backup

   rsync copies files, dd creates exact disk images, cp copies files, mv moves files.

2. Step 2: Choose command for full SD card image

   dd is used to create a full image backup of the SD card on Raspberry Pi.

3. Final Answer:

   dd -> Option B

4. Quick Check:

   Full image backup = dd [OK]

Hint: Use dd for full SD card image backups [OK]

Common Mistakes:

• Using rsync for full disk image instead of file sync
• Confusing cp or mv with disk imaging
• Not knowing dd creates exact disk copies

3. What will be the output of this command on Raspberry Pi?

rsync -av --delete /home/pi/data/ /backup/data/

medium

A. Copies files from /home/pi/data/ to /backup/data/ and deletes files not in source

B. Copies files from /backup/data/ to /home/pi/data/ without deleting

C. Deletes all files in /home/pi/data/ without copying

D. Moves files from /home/pi/data/ to /backup/data/ without copying

Solution

1. Step 1: Understand rsync options

   -a means archive (copy recursively with attributes), -v means verbose, --delete removes files in destination not in source.

2. Step 2: Analyze source and destination paths

   Files are copied from /home/pi/data/ to /backup/data/ with deletion of extra files in destination.

3. Final Answer:

   Copies files from /home/pi/data/ to /backup/data/ and deletes files not in source -> Option A

4. Quick Check:

   rsync -av --delete = sync with deletion [OK]

Hint: rsync --delete syncs source to destination exactly [OK]

Common Mistakes:

• Confusing source and destination order
• Thinking rsync moves files instead of copying
• Ignoring --delete option effect

4. You run dd if=/dev/mmcblk0 of=backup.img but get a 'Permission denied' error. What is the likely fix?

medium

A. Run the command with sudo to get admin rights

B. Change the output file name to backup.txt

C. Use rsync instead of dd

D. Restart the Raspberry Pi and try again

Solution

1. Step 1: Understand permission error cause

   Accessing /dev/mmcblk0 requires admin rights, normal user lacks permission.

2. Step 2: Fix by running with elevated rights

   Using sudo runs the command as admin, allowing access to device files.

3. Final Answer:

   Run the command with sudo to get admin rights -> Option A

4. Quick Check:

   Permission denied = need sudo [OK]

Hint: Use sudo for commands accessing system devices [OK]

Common Mistakes:

• Changing file extension does not fix permission
• Switching to rsync won't fix device access
• Restarting doesn't change permissions

5. You want to automate daily backups of your Raspberry Pi's important files to an external USB drive. Which approach is best?

hard

A. Manually copy files every day using file manager

B. Install a game that backs up files automatically

C. Use dd to create a full SD card image every hour

D. Write a script using rsync and schedule it with cron

Solution

1. Step 1: Identify automation tools on Raspberry Pi

   rsync efficiently copies files; cron schedules tasks automatically.

2. Step 2: Choose best method for daily automated backup

   Writing a script with rsync and scheduling with cron automates daily backups reliably.

3. Final Answer:

   Write a script using rsync and schedule it with cron -> Option D

4. Quick Check:

   Automate backups = rsync + cron [OK]

Hint: Use cron with rsync for automated backups [OK]

Common Mistakes:

• Relying on manual copying is not automated
• Using dd hourly wastes space and time
• Installing unrelated software won't backup files