Task 4.3 — Simple Backup

Overview

A bash script that creates timestamped, compressed backups of a given directory and automatically rotates old archives to stay within a configurable limit.

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Scripts

task4_3.sh

• Accepts two arguments: an absolute path to the source directory and the maximum number of backups to retain
• Creates the backup destination /tmp/backups/ if it does not exist
• Archives and compresses the source directory with tar + gzip
• Names the archive <dir>-<timestamp>.tar.gz, where / in the path is replaced with - and the leading separator is dropped (e.g. /etc/default → etc-default-2026-05-10-120000.tar.gz)
• After creating a new backup, deletes the oldest archives for that directory so that no more than n copies remain
• Validates both arguments and prints a descriptive message to stderr with a non-zero exit code on any error

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Additional Requirements

1. Each run must either create a backup or display an error message — silent failure is not acceptable.
2. The script must validate the argument count and the existence of the source directory. On failure it must write to stderr and exit with a non-zero code.
3. Archive name template for rotation: <archived dirname with dashes>*.tar.gz
4. The script must be uploaded to a GitHub repository named task4_3.
5. The repository must contain exactly one file: task4_3.sh in the root folder.

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Environment Setup Guide

This section describes how to spin up a local Ubuntu 16.04 environment that matches the grader's setup so you can verify the solution before submission.

Option A — Docker (recommended, works on Windows / macOS / Linux)

Prerequisites: Docker Desktop installed and running.

# 1. Pull the Ubuntu 16.04 image
docker pull ubuntu:16.04

# 2. Start a container
docker run -it --name backup-test ubuntu:16.04 /bin/bash

Inside the container:

# 3. Install prerequisites
apt-get update && apt-get install -y git

# 4. Clone the repository (replace with your actual URL)
git clone https://github.com/<your-username>/task4_3 /root/task4_3
cd /root/task4_3

# 5. Create a test directory with some content
mkdir -p /tmp/testdir && echo "hello" > /tmp/testdir/file.txt

# 6. Run the backup script — creates the first archive
bash task4_3.sh /tmp/testdir 3
ls /tmp/backups/

# 7. Run twice more to accumulate 3 backups
bash task4_3.sh /tmp/testdir 3
bash task4_3.sh /tmp/testdir 3
ls /tmp/backups/   # should show exactly 3 archives

# 8. Run a fourth time — the oldest archive must be deleted
bash task4_3.sh /tmp/testdir 3
ls /tmp/backups/   # still exactly 3 archives

# 9. Test error cases
bash task4_3.sh                       # too few args  → exit 1
bash task4_3.sh /no/such/dir 3        # missing dir   → exit 2
bash task4_3.sh /tmp/testdir abc      # invalid count → exit 3
bash task4_3.sh /tmp/testdir 3 extra  # too many args → exit 1

To re-use the container later:

docker start -ai backup-test

To start fresh:

docker rm backup-test

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Option B — Vagrant (closer to bare-metal)

Prerequisites: VirtualBox and Vagrant installed.

Create a Vagrantfile in any working directory:

Vagrant.configure("2") do |config|
  config.vm.box = "ubuntu/xenial64"
  config.vm.provision "shell", inline: <<-SHELL
    apt-get update
    apt-get install -y git
  SHELL
end

# Start and SSH into the VM
vagrant up
vagrant ssh

# Then follow steps 4–9 from Option A above (inside the VM)
sudo -i
git clone https://github.com/<your-username>/task4_3 /root/task4_3
cd /root/task4_3
bash task4_3.sh /tmp/testdir 3

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Verification Checklist

Check	Command	Expected result
Backup dir created automatically	bash task4_3.sh /tmp/testdir 3 && ls /tmp/backups/	Directory exists, archive present
Archive filename format	ls /tmp/backups/	Matches tmp-testdir-<timestamp>.tar.gz
Archive is valid gzip	file /tmp/backups/tmp-testdir-*.tar.gz	gzip compressed data
Rotation keeps exactly n files	Run script 4× with limit 3, then ls /tmp/backups/ | wc -l	3
Too few arguments	bash task4_3.sh /tmp/testdir	Prints error to stderr, exits 1
Too many arguments	bash task4_3.sh /tmp/testdir 3 extra	Prints error to stderr, exits 1
Non-existent source directory	bash task4_3.sh /no/such/dir 3	Prints error to stderr, exits 2
Non-numeric backup count	bash task4_3.sh /tmp/testdir abc	Prints error to stderr, exits 3

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Verification Procedure

Environment

• OS: Ubuntu Xenial 16.04 Server
• User: root
• Network: internet access available

Execution Rules

• The repository is cloned by URL (e.g. https://github.com/user/task4_3); a different repository name results in automatic failure.
• task4_3.sh is launched automatically from the repository root; a different script name or subdirectory location results in automatic failure.
• The script is run with multiple parameter combinations covering all error and success cases listed below.

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Expected Behavior

Successful backup run

• /tmp/backups/ is created if it does not exist.
• A new archive is created at /tmp/backups/<dir>-<timestamp>.tar.gz.
• After creation, archives for the given source directory are counted; any beyond the specified limit are deleted, oldest first.
• The script exits with code 0.

Error — wrong number of arguments

• Message printed to stderr.
• Script exits with a non-zero code.
• No backup is created.

Error — source directory does not exist

• Message printed to stderr.
• Script exits with a non-zero code.
• No backup is created.

Error — backup count argument is not a valid number

• Message printed to stderr.
• Script exits with a non-zero code.
• No backup is created.

Note: All error messages must go to stderr. Output sent to stdout will not be detected by the checker and the script will be considered non-compliant.