For enhanced security, Linux passwords are not stored in plain text but are hashed before storing. Hashing is a one-way process that converts the password into a fixed-length string of characters. This makes it difficult for attackers to reverse the process and obtain the original password.

The correct command to monitor real-time network interface statistics in Linux is iptraf. It provides detailed information about network traffic, including traffic per interface, protocols, and ports. ifconfig and netstat are used for network configuration and monitoring, but they don't offer real-time statistics. nmap is a network scanning tool.

In package management, a "Source Package" is a collection of patches, configuration files, and scripts that adapt a software source code to a particular distribution. Source packages are used to build binary packages specific to a particular Linux distribution.

To diagnose potential issues with domain name resolution, you might use the "dig" command. "dig" (Domain Information Groper) is a powerful command-line tool for querying DNS (Domain Name System) servers and obtaining detailed information about DNS records and name resolution, making it useful for troubleshooting DNS-related problems.

In Bash, the while construct allows you to execute a specific block of code repeatedly as long as a certain condition is true. It's commonly used for creating loops in Bash scripts.

The sleep command is used in a shell script to introduce a delay. You specify the number of seconds to pause the script's execution. It's commonly used for debugging to observe intermediate results or to add pauses for various purposes.

To execute a script in Bash, you often need to make it executable by running chmod +x script_name, and then you use the ./ symbol before the script name to specify the current directory. This tells the shell to execute the script from the current directory.

The command "crontab -l" is used to view the list of scheduled tasks (cron jobs) for the system. It lists the cron entries for the currently logged-in user. Scheduled tasks are used to automate various processes at specific times or intervals in a Linux system.

To restrict users from logging in via SSH, you would modify the /etc/ssh/sshd_config file. This file contains configuration options for the SSH server, and you can specify access restrictions and settings here.

SELinux (Security-Enhanced Linux) enforces mandatory access controls at the kernel level in Linux. It provides a powerful and flexible security framework that allows administrators to define fine-grained access policies for processes, files, and resources on a system.