A server, in computing, is a dedicated computer program or device providing services to other programs (clients) and users. This can include fulfilling requests and hosting applications.
In the client/server model, servers await and fulfill requests from clients, either on the same machine or across different computers.
- Physical Server: A computer solely designated for running server software.
- Virtual Server: A virtualized representation with its own OS, separated from other virtual servers on the same machine.
- Virtual machines are created using a hypervisor on a physical server.
- The hypervisor manages resources and allocates them to multiple virtual machines.
- Requires at least two components: an operating system and an application.
- Enables communication between clients and the server application.
Examples include web servers, application servers, proxy servers, mail servers, virtual servers, blade servers, file servers, policy servers, database servers, and print servers.
- Components: Rack-mount chassis, power supply, system board, CPUs, memory, storage, and network interface.
- Out-of-band management for remote monitoring and management.
- Server OS, such as Windows Server or Linux, acts as the platform for applications.
A virtual machine (VM) is a simulated representation of a physical computer. It runs its own OS and applications, allowing multiple VMs on a single physical device.
A hypervisor, or Virtual Machine Monitor (VMM), abstracts and virtualizes hardware, enabling multiple operating systems to run on the same physical machine.
- Type 1 Hypervisor (Bare Metal): Directly on hardware, e.g., VMware ESXi.
- Type 2 Hypervisor (Hosted): Runs on top of a host OS, e.g., VMware Workstation.
Involves creating and managing virtualized instances within a host machine.
- Cost efficiency
- Efficient provisioning
- Enhanced productivity
- Streamlined DevOps
- Enhanced security through isolation
- Portability for legacy applications
Debian is a stable, reliable, free, and open-source operating system with a commitment to free software principles. It uses APT for efficient package management.
Rocky Linux is a community-driven, enterprise-grade Linux distribution, designed as a downstream, binary-compatible alternative to Red Hat Enterprise Linux (RHEL).
Considerations between Debian and Rocky Linux:
- Stability and LTS
- Community and Development Model
- Package Management
- Enterprise Support and Ecosystem
- Development Model
- Release Cycle and Stability
- Package Management
- Community and Ecosystem
- Goals and Focus
APT (Advanced Package Tool) is a powerful package management system in Debian-based distributions, automating software installation, updating, upgrading, and removal.
Aptitude is a user-friendly, text-based interface for APT, offering interactive package management with features for search, filter, and dependency resolution.
- User Interface
- Usage and Commands
- Dependency Handling
- User Recommendations
- apt: A command-line tool with a simplified interface for ease of use.
- aptitude: A command-line tool with a more interactive and text-based interface.
- apt: Uses simple commands like
apt install,apt remove,apt update, andapt upgrade. - aptitude: Offers an extended set of commands and an interactive interface for more complex package management.
- apt: Utilizes the APT library for automatic dependency resolution during installations or removals.
- aptitude: Known for sophisticated dependency resolution, especially for complex issues.
- apt: Recommended for common tasks due to simplicity.
- aptitude: Considered more advanced, suitable for users preferring an interactive interface or requiring advanced features.
SSH, which stands for Secure Shell, is a cryptographic network protocol used to securely access and manage network devices, servers, and computers over a potentially unsecured network. SSH provides a secure channel over an insecure network by encrypting the communication between the client and the server.
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Encryption: SSH encrypts the data during transmission, preventing unauthorized access to sensitive information.
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Authentication: It uses cryptographic keys (public and private key pairs) for user authentication, providing a more secure method than traditional password-based logins.
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Secure File Transfer: SSH includes secure file transfer capabilities, commonly used through tools like SCP (Secure Copy Protocol) or SFTP (Secure File Transfer Protocol).
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Remote Command Execution: SSH allows users to execute commands on a remote machine securely, providing a secure and encrypted alternative to less secure remote access methods.
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Connection Establishment: The client initiates a connection to the server, and a secure connection is established using cryptographic algorithms.
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User Authentication: SSH supports various methods of user authentication, including password-based authentication and public key authentication. Public key authentication is often preferred for enhanced security.
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Secure Data Exchange: Once authenticated, the client and server exchange data over the encrypted channel, securing the communication.
To connect to a remote server using SSH, you typically use the following command in the terminal:
AppArmor, short for Application Armor, is a Linux kernel security module that restricts the capabilities of individual programs, isolating them from the rest of the system. It is a mandatory access control (MAC) system that confines programs to a limited set of resources and capabilities, reducing the potential impact of security vulnerabilities.
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Profile-Based Security: AppArmor uses profiles to define the resources and capabilities available to a specific program. Each program can have its own profile, specifying what it is allowed to do.
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Path-Based Control: AppArmor controls access based on file paths, making it effective in protecting against unauthorized access to critical system files.
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Run-Time Configuration: Profiles can be loaded and unloaded at run time without requiring a system restart. This flexibility allows administrators to adjust security policies as needed.
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Easy Adoption: AppArmor is designed to be user-friendly and easy to adopt. It provides tools for creating, modifying, and managing profiles, simplifying the process of securing applications.
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Profile Creation: Administrators define profiles for individual programs, specifying the resources and capabilities the programs need.
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Profile Enforcement: When a program is executed, AppArmor enforces the restrictions defined in its profile. If the program attempts to access resources or perform actions outside its profile, AppArmor prevents those actions.
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Logging and Auditing: AppArmor logs enforcement actions, providing administrators with information about potential security threats or misconfigurations.
To enable AppArmor and create profiles for specific applications, you can use the apparmor command-line tools. Profiles are typically stored in the /etc/apparmor.d/ directory.
sudo systemctl enable apparmor
sudo systemctl start apparmor- Enables and starts the AppArmor service on the system.
sudo apparmor_status- Displays the current status and information about enforced profiles.
Enjoy!