Backup automation script in Bash Scripting - Practice Problems & Coding Challenges

Challenge - 5 Problems

💻 Command Output

intermediate

What is the output of this backup script snippet?

Consider this bash script snippet that creates a backup of a directory and logs the result. What will be printed to the console when the script runs successfully?

Bash Scripting

backup_dir="/home/user/documents"
backup_dest="/home/user/backup"

mkdir -p "$backup_dest"
tar -czf "$backup_dest/documents_backup.tar.gz" "$backup_dir" && echo "Backup successful" || echo "Backup failed"

A tar: command not found

B Backup failed

C Backup successful

D Permission denied

💡 Hint

The tar command creates a compressed archive. If it succeeds, the echo after && runs.

The script creates the backup directory if it doesn't exist, then runs tar to compress the source directory. If tar succeeds, it prints 'Backup successful'.

📝 Syntax

intermediate

Identify the syntax error in this backup script

Which option shows the correct way to write this line to check if the backup directory exists and create it if not?

Bash Scripting

[ ! -d "$backup_dest" ] mkdir -p "$backup_dest"

A if [ ! -d "$backup_dest" ]; then mkdir -p "$backup_dest"; fi

B [ ! -d "$backup_dest" ] && mkdir -p "$backup_dest"

C if [ ! -d "$backup_dest" ]; then mkdir -p "$backup_dest" fi

D [ ! -d "$backup_dest" ]; mkdir -p "$backup_dest"

💡 Hint

Remember to use 'then' and end the if statement with 'fi'.

Option A correctly uses the if statement syntax with 'then' and ends with 'fi'. Option A misses 'then' and is missing a semicolon or line break. Option A misses semicolons. Option A is invalid syntax.

🔧 Debug

advanced

Why does this backup script fail to create the backup file?

This script is intended to create a compressed backup of /var/log but fails silently without creating the backup file. What is the cause?

Bash Scripting

backup_dir="/var/log"
backup_dest="/tmp/backup"

mkdir -p "$backup_dest"
tar -czf "$backup_dest/var_log_backup.tar.gz" "$backup_dir" > /dev/null 2>&1

if [ -f "$backup_dest/var_log_backup.tar.gz" ]; then echo "Backup created"; else echo "Backup missing"; fi

A The script lacks sudo privileges to read /var/log, so tar creates no archive.

B The redirection '> /dev/null 2>&1' causes the tar command to fail.

C The backup directory path is incorrect and mkdir fails.

D The if condition syntax is wrong and always prints 'Backup missing'.

💡 Hint

Check permissions for reading system log files.

The /var/log directory usually requires root permissions to read all files. Without sudo, tar cannot read some files, resulting in an empty or no archive. The script suppresses errors, so it fails silently.

🚀 Application

advanced

Which script snippet correctly deletes backups older than 7 days?

You want to automate deleting backup files older than 7 days in /home/user/backup. Which snippet will do this safely?

A find /home/user/backup -mtime +7 -delete

B find /home/user/backup -type f -name '*.tar.gz' -mtime +7 -exec rm {} \;

C rm /home/user/backup/*.tar.gz -mtime +7

D rm -rf /home/user/backup/*.tar.gz --older-than 7d

💡 Hint

Use find with -mtime and -exec to remove files older than a certain number of days.

Option B uses find to locate files with .tar.gz extension older than 7 days and deletes them safely. Option B is invalid syntax. Option B deletes all files and directories older than 7 days, which may be unsafe. Option B uses a non-existent rm option.

🧠 Conceptual

expert

What is the main benefit of using rsync over tar for backups in scripts?

When automating backups, why might you choose rsync instead of tar?

A rsync creates a single archive file like tar but faster.

B rsync compresses files better than tar, creating smaller archives.

C rsync automatically encrypts backups without extra configuration.

D rsync can efficiently copy only changed files, reducing backup time and storage.

💡 Hint

Think about incremental backups and copying only differences.

rsync copies only changed or new files, making backups faster and saving space. tar creates full archives every time. rsync does not compress or encrypt by default.