Leverage GIT for Network Engineer

Introduction

Git is a powerful and widely-used version control system that allows developers to track changes in their code, collaborate with others, and manage different versions of their projects. In this comprehensive guide, we will delve into the intricacies of Git, exploring its features, usage, and the steps to get started. Whether you're a beginner just starting out or a seasoned professional looking to brush up on your skills, this guide is designed to provide a clear understanding of Git.

Understanding Git

Why we need GIT? Git is a distributed version control system that allows users to track changes in files. For network engineers, these files could be network device configurations, network automation scripts, or network design documents.

By using Git, network engineers can keep track of every change made, making it easy to identify when a change was made and who made it. This is particularly useful when troubleshooting network issues or auditing changes.

Installing Git

Before you can start using Git, you need to install it on your computer. The installation process varies depending on your operating system:

- **Windows:** Download the latest Git for Windows installer and follow the prompts to install. You can download it from the official Git website.

- **Mac:** Install Git using Homebrew with the command `brew install git`. If you don't have Homebrew installed, you can install it from the Homebrew website.

- **Linux:** Use your distribution's package manager. For example, on Ubuntu or Debian, use `sudo apt-get install git`.

After installation, you can verify that Git is installed correctly by opening a terminal and typing `git --version`. This should display the installed version of Git.

Setting Up Git

Once Git is installed, you need to configure it. Start by setting your username and email, which will be used in your commits:

                              
```bash
git config --global user.name "Your Name"
git config --global user.email "youremail@example.com"
 ```
                             
These commands set the global configuration for Git, which will be used for all repositories on your machine. If you want to set the configuration for a specific repository, you can do so by running the commands without the `--global` option while in the repository's directory.

Git Basics


### Initializing a Repository To start using Git, you need to initialize a Git repository in your project's directory:

```bash
cd /path/to/your/project
git init
``` 
This creates a new Git repository in your project's directory. If you look at the directory in your file explorer, you won't see anything different. But if you show hidden files, you'll see a new `.git` directory. This is where Git stores all the information it needs to manage your repository.

Making Changes

Once your repository is set up, you can start tracking changes. Here's a basic workflow:

1. **Stage changes:** Use `git add` to stage changes for commit. You can add individual files (`git add filename`) or all changes (`git add .`).

For example, if you have a network configuration file named router-config.txt that you've made changes to, you can stage those changes with git add router-config.txt. If you've made changes to multiple files, you can stage them all with git add ..

2. **Commit changes:** Use `git commit` to save your staged changes. Always include a descriptive message (`git commit -m "Your message"`).

For example, if you've staged some changes and want to commit them, you could use git commit -m "Updated router configuration". This creates a new commit with the message "Updated router configuration".

3. **View history:** Use `git log` to view the commit history.

When you run `git log`, you'll see a list of commits in reverse chronological order. Each commit shows the author, the date, and the commit message.

Branching and Merging

Git allows you to create branches to work on different features simultaneously. Use git branch to manage branches and git checkout to switch between them. Once a feature is complete, you can merge it back into the main branch with git merge.

For example, if you're working on a new network design, you might want to create a new branch to keep your work separate. You can do this with git branch new-design. Then, to switch to your new branch, you can use git checkout new-design.

Once you've finished your design, you can merge it back into the main branch (usually called master or main). First, switch back to the main branch with git checkout master, then merge your design branch with git merge new-design.

Working with Remote Repositories

Git also allows you to work with remote repositories, which are versions of your project hosted on the internet or network. Here's how to manage them:

1. **Clone a repository:** Use `git clone` to create a local copy of a remote repository.

For example, if you want to contribute to an open-source project on GitHub, you would first clone the repository with `git clone https://github.com/user/repo.git`. This creates a new directory with the repository's contents.

2. **Pull changes:** Use `git pull` to fetch changes from the remote repository and merge them into your current branch.

If other people have made changes to the repository since you cloned it, you can get those changes with `git pull`.

3. **Push changes:** Use `git push` to send your committed changes to the remote repository.

After you've made some changes and committed them, you can share them with others by pushing them to the remote repository with `git push`.

Advanced Git Features

Git Stash

Git stash allows you to temporarily save changes that you don't want to commit immediately. You can apply the stashed changes later.

For example, if you're in the middle of working on a feature but need to switch to another branch to fix a bug, you can stash your changes with `git stash`, switch branches and fix the bug, then come back and apply your stashed changes with `git stash apply.

Git Rebase

Git rebase allows you to move or combine a sequence of commits to a new base commit. It's a way to integrate changes from one branch into another.

For example, if you have a branch `feature` that has diverged from the `main` branch, you can use `git rebase main` while on the `feature` branch to move your changes to the tip of the `main` branch. This can make the history cleaner by turning it into a linear sequence of commits.

Rebasing is a powerful feature, but it can be dangerous if not used properly. When you rebase, you're rewriting commit history. This is fine for changes that only exist on your local machine, but can cause problems if you're collaborating with others. If you've pushed your changes to a remote repository, and then rebase those commits, the history on your local machine will be out of sync with the history on the remote repository. This can lead to confusion and conflicts.

Git Tag

Git tag is used to capture a point in history that is used for a marked version release (i.e., v1.0.0).

For example, if you've reached a point where you want to release version 1.0.0 of your project, you can create a tag for that commit with `git tag v1.0.0`. You can then push this tag to the remote repository with `git push origin v1.0.0`.

Tags are a way of marking specific points in your history as being important. Typically, people use this functionality to mark release points (v1.0, v2.0 and so on).

Git Diff

The git diff command can show you what changes you've made compared with the repository's history. By default, it shows you any changes that you've made but haven't yet staged with git add.

For example, if you've modified a network configuration file called router-config.txt, but haven't staged it yet, you can see what you've changed with git diff router-config.txt

Git Fetch

The `git fetch` command allows you to pull down data from your remote repositories. It's similar to `git pull`, but instead of automatically merging the changes into your current branch, it simply retrieves the data, allowing you to review the changes before integrating them.

For example, if you want to see what changes have been made in the remote repository without merging them into your current branch, you can use `git fetch origin`.

Use Case: Network Configuration Management with GitLab and Python

In the world of network engineering, managing network configurations can be a daunting task, especially in large-scale environments. This is where GitLab, a web-based DevOps lifecycle tool that provides a Git-repository manager, comes into play. Coupled with Python, a powerful scripting language, network engineers can automate network configuration tasks and keep track of changes using GitLab. Let's delve into a practical use case.

Scenario

Let's consider a scenario where a network engineer is responsible for managing the configurations of hundreds of routers in a network. The configurations need to be updated regularly and any changes should be tracked for auditing purposes. To automate this task, the engineer decides to write a Python script that can apply configurations to the routers. The script and the configurations are stored in a GitLab repository.

Step 1: Creating the Python Script The network engineer writes a Python script using a library like Netmiko, which simplifies the process of connecting to network devices over SSH. The script reads a configuration file and applies the configuration to a list of routers.

Here's a simplified example of what the script might look like:

```python
from netmiko import ConnectHandler

def apply_config(device, config):
    connection = ConnectHandler(**device)
    output = connection.send_config_from_file(config)
    print(output)
    connection.disconnect()

device = {
    'device_type': 'cisco_ios',
    'ip':   '10.0.0.1',
    'username': 'admin',
    'password': 'password',
}

config = 'path/to/config.txt'

apply_config(device, config)
```
This script connects to a router and applies the configuration from a file.

Step 2: Storing the Script and Configurations in GitLab

The network engineer creates a new GitLab repository and pushes the Python script and the configuration files to the repository. This allows the engineer to keep track of any changes made to the script or the configurations.

Here are the Git commands to add the files to the repository and push them to GitLab:

```bash
git add apply_config.py config.txt
git commit -m "Initial commit of script and configuration"
git push origin master
```
Step 3: Running the Script Step 3: Running the Script

Whenever the network engineer needs to apply the configurations, they can pull the latest version of the script and the configurations from GitLab and run the script:

```bash
git pull origin master
python apply_config.py
```    
Step 4: Tracking Changes

Any changes made to the script or the configurations are committed and pushed to GitLab. This provides a historical record of all changes, which can be useful for auditing purposes or if a previous configuration needs to be restored.

For example, if the configuration file is updated, the changes can be committed and pushed to GitLab:

```bash
git add config.txt
git commit -m "Updated router configuration"
git push origin master
```    
By using GitLab and Python, the network engineer has automated the task of managing network configurations and has a robust system for tracking changes. This not only saves time but also reduces the risk of errors that could occur when managing configurations manually.

GIT Useful commands

Conclusion:

Git is an indispensable tool in the modern network engineer's toolkit. It provides a robust and reliable way to manage and track changes in network configurations, scripts, and documentation. By leveraging Git, network engineers can enhance collaboration, maintain historical records, and improve overall productivity.

In this blog, we've explored the basics of Git, delved into some advanced features, and even walked through a practical use case of managing network configurations with GitLab and Python. We hope this guide has provided you with a clear understanding of how to use Git effectively in your network engineering tasks.

As we continue to explore the world of network engineering, we'll delve deeper into automation and how it can revolutionize the way we manage and operate networks. So, stay tuned for our upcoming blogs where we'll continue to unravel the power of automation in network engineering.

Remember, the key to mastering Git, like any tool, is consistent practice and usage. Don't be afraid to experiment and make mistakes - that's part of the learning process. And remember, Git is a tool designed to help you, not to make your life harder. If you're ever struggling with a complex rebase or merge conflict, remember that there's likely a simpler solution, and don't hesitate to ask for help.

Thank you for reading, and happy coding!