Linux Commands for DevOps

3. Why is Linux used for DevOps?

In the DevOps universe, where agility and efficiency reign supreme, there's one true rockstar that steals the show—Linux! Why? Because Linux is the ultimate performer that brings unparalleled power and flexibility to your DevOps stage.

Linux is like the backstage maestro, ensuring smooth operations and harmonious collaboration between development and operations teams. Its stability, security, and open-source nature make it the go-to choice for DevOps enthusiasts worldwide.

With Linux, you have a powerful toolkit of command-line wizardry at your fingertips. From managing packages with a flick of a command to orchestrating complex deployments like a conductor leading an orchestra, Linux commands make your life as a DevOps rockstar a breeze.

But that's not all! Linux is the ultimate team player, seamlessly integrating with a wide range of DevOps tools and technologies. Whether you're diving into containerization with Docker or automating infrastructure provisioning with Terraform, Linux is there, cheering you on and ensuring your success.

Just like a true rockstar, Linux commands know how to steal the spotlight. They allow you to automate repetitive tasks, fine-tune configurations, monitor system performance, and deploy applications with precision and finesse. You become the guitar-wielding hero, shredding through DevOps challenges with ease.

So, why is Linux the undisputed star of DevOps? It's simple—Linux sets the stage for seamless collaboration, automation, and innovation. It empowers you to deliver software faster, smoother, and with the rockstar flair that only Linux can provide.

4. What makes Linux so popular?

Linux has gained immense popularity due to several key factors:

a. Open-Source Nature: Linux is an open-source operating system, which means that its source code is freely available for anyone to view, modify, and distribute. This has resulted in a large and active community of developers who contribute to the development and improvement of Linux, creating a robust ecosystem of software, utilities, and applications. The open-source nature of Linux fosters innovation, collaboration, and community-driven development, which has led to its widespread adoption and popularity.

b. Flexibility and Customization: Linux is known for its flexibility and customization options. Users can configure Linux-based systems to suit their specific needs, from selecting different distributions (or "distros") with varying configurations and packages to customizing the kernel, software stack, and system settings. This flexibility allows users to tailor Linux to their requirements, making it a popular choice for a wide range of use cases, from embedded systems to servers and desktop computers.

c. Stability and Reliability: Linux is renowned for its stability and reliability, making it suitable for mission-critical applications and production environments. Linux-based systems are known for their uptime, performance, and scalability, making them ideal for running servers, data centers, and cloud computing platforms. Linux also has a robust update and patching system, ensuring that the OS and its components are regularly updated with security fixes and improvements.

d. Security: Linux is known for its strong focus on security. The open-source nature of Linux allows for extensive community-driven security audits, resulting in the timely identification and patching of vulnerabilities. Linux also has robust access controls, permissions management, and auditing capabilities, making it a secure choice for sensitive environments. Additionally, Linux provides features such as mandatory access controls (e.g., SELinux), which enhance the security posture of Linux-based systems.

e. Broad Hardware and Platform Support: Linux supports a wide range of hardware architectures, making it versatile and adaptable to different devices, from servers and desktop computers to embedded systems and IoT devices. Linux also has extensive support for cloud computing platforms, containerization technologies, and virtualization, making it a popular choice for modern computing environments.

f. Large and Active Community: Linux has a large and vibrant community of users, developers, and enthusiasts who contribute to its development, support, and advocacy. This community-driven approach results in continuous improvement, extensive documentation, and widespread adoption of Linux in various industries, including technology, finance, healthcare, education, and more. The active community provides support, knowledge-sharing, and collaborative development, making Linux a reliable and popular choice for many users and organizations.

To summarize, the open-source nature, flexibility, customization options, stability, security, broad hardware and platform support, and active community are some of the key factors that have contributed to the popularity of Linux as an operating system. Linux has emerged as a reliable, versatile, and widely-used choice for a wide range of applications, from servers and cloud computing to embedded systems and IoT devices.

5. Linux Commands for DevOps

As a DevOps professional, you may need to work with various Linux commands to manage servers, automate tasks, and deploy applications. Here are some common Linux commands that are commonly used in DevOps workflows:

Note: Each command is followed by an example.

• ls: Lists files and directories in the current directory.

Output:

• cd: Changes the current directory.

Output:

• pwd: Prints the current working directory.

Output:

• mkdir: Creates a new directory.

Output:

• touch: Create a new empty file with the given name.

Output:

• rm: Removes files or directories.

Output:

Here are the different uses of the rm command:

1) Remove a File: To delete a single file, you can use the basic rm command followed by the filename. This command will permanently remove the specified file from the system.

2) Remove Multiple Files: You can delete multiple files at once by providing their filenames as arguments to the rm command. This command will remove all the specified files from the system.

3) Remove a Directory: To delete an empty directory, you can use the rm command with the -doption followed by the directory name. This command will remove the specified empty directory from the system.

4) Remove a Directory and Its Contents: To delete a directory along with all its contents (subdirectories and files), you can use the rm command with the -r option (recursive). This command will recursively remove the specified directory and all its contents from the system.

5) Prompt for Confirmation: By default, the rm command deletes files and directories without asking for confirmation. However, you can use the -i option to prompt for confirmation before deleting each file. This command will ask for confirmation before deleting the specified file.

6) Forceful Removal: In some cases, you might need to forcefully remove files or directories without being prompted for confirmation. You can use the -f option to override any warnings or prompts. This command will forcefully and recursively remove the specified directory and its contents without asking for confirmation.

Note: Exercise caution when using the rm command, especially with the -r and -f options, as it permanently deletes files and directories, making recovery difficult. Always double-check the files and directories you are deleting to avoid accidental data loss.

• cp: Copies files or directories. The first argument is the source and the second argument is the destination where you want to copy. To copy folders, you need to pass -r as flag as well.

Output:

• mv: Moves or renames files or directories. The first argument is the source and the second argument is the destination where you want to copy.

Output:

-- Differences between cp and mv commands Highlighting the differences between the cp and mv commands:

Imagine you have a collection of beautiful paintings in your house, and you want to organize them in different rooms. You have two magical tools at your disposal: the cpwand and the mv wand. Let's see how they differ in their enchanting abilities.

The Copying Spell with cp: When you use the cp command, it's like casting a duplication spell. It creates an exact copy of your painting, allowing you to have multiple versions in different locations. It's perfect when you want to preserve the original artwork while making duplicates.

Here are the key features of the cp command:

• Preservation of the Original: When you use cp, the original file or directory remains intact. A new copy is created, allowing you to have identical content in multiple locations.

• Multiple Copies: You can create multiple copies of a file or directory using cp. Each copy is an independent entity, and changes made to one copy do not affect the others.

• Destination Flexibility: With cp, you can specify a different name or location for the copied file or directory. It provides flexibility in organizing and managing your files.

The Moving Spell with mv: On the other hand, when you invoke the power of the mv command, it's like performing a teleportation spell. It magically transports your painting from one location to another, without leaving behind any duplicates. It's ideal when you want to relocate your painting to a new spot or room. Suppose you decide to move a captivating portrait from the living room to the hallway, where it can captivate passersby. The mv command gracefully lifts the painting and transports it seamlessly to its new home, ensuring that only one instance of the artwork exists, preserving its uniqueness.

Here are the key features of the mv command:

• Relocation: When you use mv, the source file or directory is moved to a new location. It is no longer present in the original location after the move operation.

• Single Instance: Unlike cp, mv does not create copies. It preserves the original file or directory and transfers it to a new location, maintaining a single instance.

• Renaming Capability: Along with relocation, mv allows you to change the name of the file or directory during the move operation. This enables you to simultaneously move and rename the item.

In essence, the key differences between cp and mv can be summarized as follows:

• cp creates duplicates of files or directories, allowing you to have multiple copies in different locations.
• mv moves files or directories, transferring them from one location to another, without leaving behind duplicates.

Both commands possess their own magical charm, but it's important to choose the right spell based on your intention. Whether you wish to duplicate and preserve the original with cp or teleport and relocate the item with mv, these commands provide you with the enchanting powers to organize your digital world effortlessly.

$ 1s -1

drwxr-xr-x. 4 root root 68 Jun 23 15:15 tuned -rw-r--r--. 1 root root 4017 Jun 23 2023 vimrc

• chmod: Changes permissions of files or directories.

Output:

-- Working of chmod 700 bin/

Imagine you have a special secret room in your house called "bin," where you keep all your valuable treasures. Now, you don't want just anyone to be able to access this room, so you need to set some rules. That's where the chmod 700 bin/ command comes into play.

The chmod command stands for "change mode," and it allows you to change the permissions of a file or directory. In this case, you're applying it to the "bin" directory.

The number "700" is like a magical combination lock for your secret room. It's made up of three digits that each represent a different group of people: the owner, the group, and everyone else.

Let's break it down:

The first digit,7, refers to the owner of the "bin" directory. It's the highest permission level possible, and it means that the owner has complete control. They can do anything they want in that room—open, modify, delete, or add treasures.

The second digit, 0, represents the group. In this case, you're giving the group absolutely no permissions. They can't even peek inside the room. It's like they don't have a key at all.

The third and final digit, 0, stands for everyone else who is not the owner or in the group. It means they also have no permissions. They can't even approach the room, let alone enter or see what's inside.

So, in simple terms, when you run chmod 700 bin/, you're essentially saying, "Hey, magical combination lock, I want to make sure that only I, the owner, have full access to my secret room. The group and everyone else can't touch it."

By using this command, you're carefully defining who can interact with the "bin" directory and what actions they can perform. It helps in maintaining security and controlling access to sensitive files and directories on your computer system.

-- Problem and solution regarding chmod 700 bin/

Let's consider a specific problem scenario and its solution related to the chmod 700 bin/ command:

Problem: You execute the chmod 700 bin/ command but encounter a "Permission Denied" error.

Solution: The "Permission Denied" error typically occurs when you don't have the necessary privileges to modify the permissions of the "bin" directory. To resolve this issue, you can try the following steps:

1) Verify Ownership: Check the ownership of the "bin" directory using the ls -l command. Make sure you are the owner of the directory or have sufficient permissions as a superuser (e.g., root) to modify its permissions. If you're not the owner, you can use the chown command to change the ownership or consult the owner/administrator for assistance.

2) Use Superuser Privileges: If you're not the owner of the "bin" directory or don't have sufficient permissions, you can try executing the chmod command with superuser privileges. Prepend the command with sudo, which allows you to run commands with administrative privileges. For example: sudo chmod 700 bin/.

3) Confirm Filesystem Type: In some cases, the filesystem on which the "bin" directory resides might be mounted with certain restrictions or specific permissions. Ensure that the filesystem supports the modification of permissions and is not mounted in read-only mode. You can check the mount options using the mount command.

4) Contact System Administrator: If you are unable to modify the permissions even with superuser privileges or encounter any other issues, it's recommended to contact the system administrator or the person responsible for managing the system. They can help troubleshoot the problem, identify any specific restrictions or configurations, and provide the necessary permissions or guidance to modify the permissions effectively.

• sudo: Provides administration permissions. May need to enter password.

Output:

• grep: Searches for patterns in files. Suppose we have a file "example.txt" with the following text in it.

To search for a pattern "example" in this file, we run the following command:

Output:

• tar: Creates or extracts tar archives.

For this you need to have some .tgz file. We can then use the above command to extract the contents of it.

• wget: Downloads files from the internet.

Output:

• curl: Transfers data to or from a server.

The output has been truncated here.

Output:

• ssh: Connects to remote servers using Secure Shell protocol.

• scp: Copies files securely between local and remote systems.

• top: Displays real-time information about system processes.

Output:

• ps: Lists currently running processes.

Output:

• kill: Sends signals to terminate processes. We pass process_id as an argument.

• systemctl: Manages system services and daemons.

• journalctl: Views system logs.

• ifconfig: Configures network interfaces.

The output has been truncated here.

Output:

• iptables: Configures firewall rules.

Output:

• sed: Edits files using regular expressions.

• awk: Processes text files and performs pattern-based operations.

These are just some of the many Linux commands used in DevOps workflows. Depending on your specific requirements and the tools used, you may need to use additional commands or tools for your tasks. It's always a good practice to consult official documentation and resources for detailed information about specific commands and their usage.