Linux, an open-source operating system that powers environments ranging from servers and supercomputers to embedded systems, depends extensively on its command-line interface (CLI) for management and automation. In contrast to graphical user interfaces (GUIs), the Linux terminal provides unmatched efficiency, adaptability, and accuracy. Understanding key Linux commands is crucial for navigating the filesystem, managing processes, and troubleshooting issues.
This article explores several essential Linux commands, grouped by category, with their primary functions and practical examples. Focusing on commands that form the backbone of daily Linux operations. By the end, you'll see how to apply in a real-world case study.
Before initiating development in the Linux terminal, it is considered best practice to operate from the root directory by running this command sudo su. This provides elevated privileges required to update system packages and install dependencies essential for application execution.
sudo su
Execute the command apt-get update to synchronize the local package index with the repositories. This operation refreshes metadata for all available packages, ensuring the system references the latest versions.
apt-get update
At this stage, essential software packages and utilities such as NGINX and Vim can be installed. The command apt install nginx provisions NGINX, a high-performance web server that also functions as a reverse proxy, load balancer, and caching solution to optimize application delivery.
Similarly, apt install vim installs Vim, an advanced and extensible text editor derived from Vi, widely used for efficient code and configuration file editing in Linux environments.
apt install nginx
apt install vim
When the terminal output becomes cluttered with excessive command history, execute the clear command to reset the display buffer and present a clean workspace.
Navigation and Directory Management
These commands facilitate navigation within the Linux filesystem, enabling directory creation, traversal, and hierarchical organization.
Utilize the mkdir command to provision three new directories within the filesystem.
mkdir dir1 dir2 dir3
Execute the ls command to display the directories that were recently created within the current filesystem path.
Now you can see the 3 directories we just created dir1, dir2 and dir3.
Initially, it is necessary to navigate to the target directory using the cd command.
cd dir1
To inspect file system metadata, including both standard and hidden entries, the commands ls -l and ls -la are utilized. The ls -l command outputs detailed attributes of visible files and directories, whereas ls -la extends this listing to include hidden entries.
ls -l
ls -la
Notice the dotfiles along the directory we created with their associated metadata.
When navigating the filesystem, the cd .. command moves the user one level up to the parent directory of the current working path, whereas the cd ~ command resolves directly to the user’s home directory, independent of the current location within the filesystem.
cd ..
Notice we moved a step further to the parent directory of the current directory.
cd ~
To displays the absolute path of the current directory in which the user is working, we will use the command pwd which stands for “print working directory.”.
Files and Directory Operations
Since the newly created directories are empty, the next step is to create a file, duplicate and relocate it into one of the target directories, and then open it in a text editor for further modifications.
The touch filename command is used to create an empty file.
Notice, we have to run the ls command afterwards to list out the files and directories we created.
touch datafile.txt
To duplicate the newly created file into another directory, the cp filename.txt dir2 command is used, which preserves the original file in its current location while placing a copy in the target directory. In contrast, the mv filename.txt dir2 command relocates the file entirely into dir2, removing it from the source path. Functionally, cp behaves like a copy operation, whereas mv is analogous to a cut-and-paste.
cp datafile.txt dir2
mv datafile.txt dir2
After executing the ls command to verify the directory contents, you will observe that the file has been relocated to dir2.
On like the touch command vim filename.txt command not only creates the file (if it does not already exist) but also opens it in the Vim editor for further modifications.
vim datafile.txt
When the command is executed, it opens the file in the Vim editor. Press i to enter Insert mode and make your changes. Once editing is complete, press Esc to return to Normal mode, then type :wq and press Enter to write the changes to disk and exit the editor.
To display the contents of the recently edited file, use the cat filename command.
cat datafile.txt
If a directory is no longer required, it can be removed using the rmdir dir command. However, rmdir only deletes empty directories; to remove a directory along with its contents (files and subdirectories), the rm -r dir command must be used. In contrast, the rm filename command removes individual files.
rm datafile
To delete an individual file
rm -r dir1
To delete a directory with it's content
rmdir dir3
To delete an empty directory
Finally, grep is a robust command-line utility designed for pattern matching and text search within files or command outputs. It functions as the Linux terminal’s built-in search mechanism, enabling efficient filtering and extraction of relevant information from large datasets or command results.
Using delete as the search word.
grep delete newfile.txt
System Information and Management
Among the vast array of Linux commands, those dedicated to system information and management stand out for their ability to deliver real-time insights and control over hardware, processes, and software.
The uname -a command provides a comprehensive summary of system-level information, including kernel name, release, version, and hardware architecture details.
uname -a
To verify the storage capacity of the system, the df -h command is executed. This command reports disk space usage for all mounted filesystems, presenting the information in a human-readable format with size units.
df -h
The free -h command provides a detailed summary of the system’s memory utilization, including both RAM and swap space, in a human-readable format. It displays the total, used, free, and available memory, along with buffer/cache usage.
free -h
The top command is used to display active processes and monitor real-time system resource utilization. It provides a continuously updated, dynamic view of process activity, including CPU and memory consumption. Functionally, top serves as a terminal-based equivalent of a task manager in Linux.
top
Note: To terminate a running process in the terminal, use Ctrl+C, which sends a SIGINT (interrupt signal) to stop execution. Alternatively, Ctrl+Z suspends the process by sending a SIGTSTP signal, pausing its execution and placing it in the background.
Mastering Linux commands is not just about memorization. it’s about building intuition for how the operating system interacts with files, processes, and resources. From navigating the filesystem to monitoring system performance and controlling processes, these commands form the foundation of efficient system administration.
By consistently practicing and combining these tools, administrators and developers can transform Linux from a basic operating system into a powerful, precision-driven environment for managing modern workloads.
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