Day 5 Task: Advanced Linux Shell Scripting for DevOps Engineers with User Management

Create Directories Using Shell Script:

• Example : When executed as ./createDirectories.sh day 1 90, it creates 90 directories as day1 day2 day3 ... day90.

•   #!/bin/bash
  
    for ((i=1; i<=90; i++ ));
    do
            dirname="day$i"
            mkdir "$dirname"
            echo "created directory : $dirname"
    done
  

  Create a Script to Backup All Your Work:

  • Backups are an important part of a DevOps Engineer's day-to-day activities. The video in the references will help you understand how a DevOps Engineer takes backups

  •   #!/bin/bash
    
      backup_dir="/path/to/backup"
      source_dir="/path/to/source"
    
      # Create a compressed backup file with timestamp
      tar -czf "$backup_dir/backup_$(date +%Y%m%d_%H%M%S).tar.gz" "$source_dir"
    
      echo "The backup is completed successfully"
    

    • #!/bin/bash: Shebang line that specifies the script should be interpreted by Bash.

    • backup_dir="/path/to/backup": Variable that holds the path to the backup directory.

    • source_dir="/path/to/source": Variable that holds the path to the source directory to be backed up.

    • tar -czf "$backup_dir/backup_$(date +%Y%m%d_%H%M%S).tar.gz" "$source_dir": Creates a compressed archive (tar.gz) named with a timestamp ($(date +%Y%m%d_%H%M%S)) inside the specified backup directory ($backup_dir), containing the contents of the source directory ($source_dir).

    • echo "The backup is completed successfully": Prints a message indicating the backup process is complete.

3. Cron and Crontab to Automate the Backup Script:

A crontab (Cron table) in shell scripting is a configuration file used to schedule and automate tasks (Cron jobs) to run at specified times or intervals.

        * * * * * command_to_execute
        - - - - -
        | | | | |
        | | | | +----- day of week (0 - 7) (Sunday=0 or 7)
        | | | +------- month (1 - 12)
        | | +--------- day of month (1 - 31)
        | +----------- hour (0 - 23)
        +------------- minute (0 - 59)

        crontab -e
        0 5  * /path/to/backup.sh

Above code is defined in way that it will run 5 AM every day every month and every week.

        0: At minute 0
        5: At hour 5 AM
        *: Every day of the month
        *: Every month
        *: Every day of the week

4. User Management:

In Linux, users are accounts used for tasks, each identified by a unique User ID (UID). System users have IDs from 0 to 999, while regular users start from 1000. Users are created with useradd, and their details, including usernames, can be checked in cat /etc/passwd or using the id command.

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