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Linux is a powerful, reliable, and highly customizable open-source operating system. It’s widely used in servers, mainframes, and supercomputers worldwide, as well as in embedded systems like routers, automation controls, televisions, digital video recorders, and more. Knowing how to work with the Linux command line is a vital skill, especially for those contemplating a career in cybersecurityCybersecurity refers to the practice of protecting computers, servers, mobile devices, electronic systems, networks, and data from digital attacks, damage, or unauthorized access. It encompasses techniques to prevent cyber threats....
This tutorial will guide you through the top 10 most commonly used Linux commands, explaining what they do and how to use them.
ls (List)
ls is a basic command that lists all files and directories in the current directory.
Example:
ls- For advanced usage, you can use options like -l to get detailed information, -a to show hidden files, and -h to view file sizes in a ‘human-readable’ format.
Example:
ls -lahcd (Change Directory)
cd allows you to navigate between directories.
Example:
cd /home/user/Documents- For advanced usage, cd without any arguments will take you back to your home directory, and cd – will take you to the previous directory.
Example:
cd
cd -
pwd (Print Working Directory)
pwd displays the full pathname of the current directory.
Example:
pwd- It doesn’t have many advanced options, but it’s useful when you’re navigating through complex directory structures.
cat (Concatenate)
cat displays the content of files.
Example:
cat file.txt- For advanced usage, you can use cat to concatenate multiple files into one. You can also use it with ‘>’ to create new files.
Example:
cat file1.txt file2.txt > newfile.txt5. cp (Copy)
cp copies files and directories.
Example:
cp source.txt destination.txtmv (Move)
mv moves or renames files and directories.
Example:
mv oldname.txt newname.txt- For advanced usage, you can use -i to prompt before overwriting, similar to cp.
Example:
mv -i source.txt destination.txtrm (Remove)
rm removes files and directories.
Example:
rm file.txt- For advanced usage, use -r to remove directories and their contents recursively, -f to force removal without confirmation, and -i for interactive mode, where you’re asked for confirmation before each removal.
Example:
rm -rfi directory_to_removetouch (Change File Timestamps)
touch is used to create new empty files and to change the timestamps of existing files.
Example:
touch newfile.txt- If you specify a file that already exists, touch will update its access and modification times.
grep (Global Regular Expression Print)
grep searches for a pattern in files or input, using regex if necessary.
Example:
grep 'pattern' file.txt- For advanced usage, use -i for case-insensitive search, -r or -R for recursive search, and -l to just print filenames with matching lines.
Example:
grep -irl 'pattern' /home/user/- For advanced usage, use -i for case-insensitive search, -r or -R for recursive search, and -l to just print filenames with matching lines.
sudo (SuperUser DO)
sudo allows a permitted user to execute a command as the superuser or another user, as specified in the sudoers file.
Example:
sudo apt-get update- For advanced usage, sudo -s gives a root shell (if allowed in the sudoers file), and sudo -u [user] [command] allows running commands as another user.
Example:
sudo -s
sudo -u user commandWhy is a Good Working Knowledge of Linux Essential for Cybersecurity?
Understanding the Linux environment is fundamental to a career in cybersecurity for several reasons:
- Popularity in Server Environments: Linux powers a significant percentage of web servers worldwide. Understanding how to navigate and secure these systems is critical.
- The versatility of Tools: Many cybersecurity tools (like Nmap, Wireshark, and Metasploit) are designed with Linux in mind, or even exclusively for Linux.
- Open-Source Nature: Linux is open-source, which means its code can be inspected for vulnerabilities. This transparency is a valuable trait for security.
- Permissions and Access Controls: Linux’s robust user permission and access control model allows for fine-grained control over who can access what, a critical feature in managing security.
- Scripting and Automation: Proficiency in shell scripting allows cybersecurity professionals to automate many tasks, and many Linux distributions come with powerful scripting languages pre-installed.
The more comfortable you are with Linux, the better you’ll be at understanding and securing systems in a professional cybersecurity setting.
