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DevOps Day 10
Automating Backups with a Bash Script


Today I was tasked with creating a bash script to automate website backup, a task that required preparing the server environment for seamless automation. Successful automation involves setting prerequisites and writing the script, which is crucial for a successful automation. Today I learned that a strong foundation is essential for successful automation.

Table of Contents



The Task

I needed to create a bash script called news_backup.sh on App Server 2 to handle a multi-step backup. Requirements:

  1. Script location → /scripts directory.
  2. Backup website files → /var/www/html/news into a .zip archive.
  3. Archive name → xfusioncorp_news.zip, saved locally in /backup.
  4. Copy archive → Transfer it to the Nautilus Backup Server into /backup.
  5. Password-less execution → My user (steve) must run it without prompts.
  6. Prerequisite → zip utility must be installed manually before running the script.
  7. Restriction → No sudo allowed inside the script.



My Step-by-Step Solution

- I broke my approach into two distinct phases: preparing the environment and then writing the script.

Part 1: The Critical Prerequisite Setup

- I performed these one-time setup steps on App Server 2 as the steve user.

  1. Install zip: The task required the zip utility for archiving. 

    sudo yum install -y zip

  2. Create and Own Directories: The script needed a home (/scripts) and a place to store backups (/backup). I created them with sudo and then immediately changed their ownership to my user, steve. This was a key step to ensure my script could write to these locations without needing sudo. 

    sudo mkdir -p /scripts /backup
sudo chown steve:steve /scripts /backup

  3. Establish Password-less SSH: This was the most important prerequisite. To allow my script to copy a file to the backup server automatically, I set up SSH key-based authentication.

    • First, I generated a key pair for my user on App Server 2: 
      ssh-keygen -t rsa
# I pressed Enter for all prompts to accept defaults and set no passphrase.
    • Next, I used the ssh-copy-id utility to send my public key to the Nautilus Backup Server. I had to enter the backup server user's (clint) password one last time to authorize this. 
      ssh-copy-id clint@stbkp01
    • Finally, I tested the connection to make sure it was truly password-less. 
      ssh clint@stbkp01
# It logged me in instantly. Success! I typed 'exit' to return.

Part 2: Writing the Backup Script

- With the environment fully prepared, I was ready to write the script.

  1. Create and Edit the Script: I created an empty, executable file in the correct location. 

    touch /scripts/news_backup.sh
chmod +x /scripts/news_backup.sh
vi /scripts/news_backup.sh

  2. The Script Content: I added the following code into the file. I made sure to add comments to explain what each part of the script does. 

    #!/bin/bash

# This script creates a zip archive of the website directory,
# saves it to a local backup folder, and then securely copies
# it to a remote backup server.

# Step 1: Create a recursive zip archive of the website files.
# The archive is saved to the /backup directory.
zip -r /backup/xfusioncorp_news.zip /var/www/html/news

# Step 2: Copy the created archive to the backup server.
# This scp command works without a password because of the
# prerequisite SSH key setup.
scp /backup/xfusioncorp_news.zip clint@stbkp01:/backup/

  3. Execution and Verification: After saving the script, I ran it and verified its success at each stage. 

    # Execute the script
/scripts/news_backup.sh

# Verify the local backup was created
ls -l /backup/xfusioncorp_news.zip

# Verify the remote backup was copied successfully
ssh clint@stbkp01 "ls -l /backup/xfusioncorp_news.zip"
    Both verification commands showed the xfusioncorp_news.zip file, confirming my script had worked perfectly.



Why Did I Do This? (The "What & Why")

- Bash Scripting: This is the universal language for automation on Linux. By writing a script, I created a repeatable, reliable process that eliminates the chance of human error that comes with typing commands manually. - zip Command: Compresses files into a single archive. Using -r ensures all contents of /var/www/html/news are included, making storage and transfer easier. - scp (Secure Copy): Copies files between servers securely over SSH. It’s the standard tool for simple, safe file transfers.



Deep Dive: Why Password-less SSH is Non-Negotiable for Automation

Automation must run without human intervention — a script that stops for a password is broken.

  • Public Key Authentication → The industry-standard solution.
  • The Trust Relationship → Using ssh-copy-id, I placed a “public lock” from App Server 2 onto the Backup Server.
  • The Secure Handshake → When scp runs, App Server 2 proves its identity using its private key.
  • Seamless Execution → The Backup Server verifies it and allows the file transfer instantly, no password needed.

This is how tools like Ansible, Jenkins, and scripts can manage servers automatically.



Common Pitfalls

- Forgetting to Install zip: The script would fail immediately at the zip command. - Incorrect Permissions: Without chown on /scripts and /backup, steve couldn’t create the script or archive, causing “Permission denied” errors. - Skipping the SSH Key Setup: Without keys, scp would stop and ask for a password, breaking automation. - Using sudo in the Script: Proper ownership and permissions are safer and cleaner than embedding sudo.



Exploring the Commands Used

- sudo yum install -y zip: Installs the zip utility. - sudo mkdir -p /path: Creates a directory and any parent directories that don't exist. - sudo chown user:group /path: Changes the owner and group of a file or directory. - ssh-keygen -t rsa: Generates a new SSH key pair. - ssh-copy-id user@host: Copies the public key to a remote host to enable password-less login. - chmod +x /path/to/script.sh: Makes a script executable. - zip -r [archive.zip] [directory_to_zip]: Recursively creates a zip archive. - scp [source_file] [user@host:destination_path]: Securely copies a file to a remote host.