CentOS 7 Release Date & Key Features

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CentOS 7: A Deep Dive into Release and Key Features

CentOS 7, a highly anticipated release of the popular enterprise-grade Linux distribution, officially hit the shelves on July 7, 2014. This release marked a significant shift for CentOS, bringing substantial changes and improvements that solidified its position as a robust and reliable operating system for servers, workstations, and more. It was derived from the source code of Red Hat Enterprise Linux (RHEL) 7, inheriting its stability and long-term support. Let’s delve into the key features that defined this impactful release.

Release Date: July 7, 2014

The release followed a period of community testing and refinement, ensuring a stable and functional distribution upon its official launch. This date marked the beginning of a long support lifecycle, with mainstream support lasting until June 30, 2024, demonstrating the commitment to long-term stability that CentOS is known for.

Key Features:

CentOS 7 introduced a host of new features and updates, drastically changing the system compared to its predecessor, CentOS 6. Here are the most prominent ones:

  1. Systemd Initialization System: This was arguably the most significant change. CentOS 7 adopted systemd as its default init system, replacing the traditional SysVinit. systemd offers several advantages:

    • Parallelization of Startup Processes: systemd can start services concurrently, significantly reducing boot times compared to the sequential startup of SysVinit.
    • Improved Service Management: systemctl provides a unified command-line interface for managing services, offering more control and information compared to the older service and chkconfig commands. It offers features like starting, stopping, restarting, enabling, disabling, and querying the status of services.
    • Dependency Management: systemd explicitly defines dependencies between services, ensuring they start in the correct order and handle failures more gracefully.
    • cgroups Integration: systemd leverages Linux Control Groups (cgroups) to manage resource allocation (CPU, memory, I/O) for services, improving system stability and preventing runaway processes from consuming excessive resources.
    • Journald Logging: systemd includes journald, a binary logging system that provides more efficient and structured logging compared to traditional syslog. It allows for better filtering, searching, and analysis of system logs.

  2. Kernel 3.10: CentOS 7 shipped with the Linux kernel version 3.10. This kernel brought numerous improvements, including:

    • Enhanced Performance: Optimizations in the kernel led to better overall system performance, especially in areas like networking and storage.
    • Improved Hardware Support: The 3.10 kernel included support for newer hardware, expanding the range of devices compatible with CentOS 7.
    • Btrfs Enhancements: While not the default filesystem, Btrfs received significant improvements in stability and features in this kernel release.
    • Security Enhancements: The kernel incorporated various security updates and hardening measures.

  3. XFS as the Default Filesystem: CentOS 7 switched to XFS as the default filesystem, replacing ext4. XFS is a high-performance journaling filesystem designed for large filesystems and high throughput. Key advantages of XFS include:

    • Scalability: XFS is designed to handle extremely large filesystems (up to 8 exabytes on 64-bit systems).
    • Performance: XFS provides excellent performance, particularly for large files and high I/O workloads.
    • Online Defragmentation: XFS supports online defragmentation, allowing you to optimize the filesystem without taking it offline.
    • Metadata Checksumming: XFS incorporates metadata checksumming to enhance data integrity and detect corruption.

  4. Docker Integration: CentOS 7 included built-in support for Docker, a containerization technology. This allowed users to easily deploy and manage applications in isolated containers, improving portability and resource utilization. Docker support was a significant step towards embracing modern application deployment methodologies.

  5. GRUB2 Bootloader: CentOS 7 replaced the legacy GRUB bootloader with GRUB2. GRUB2 offers several improvements:

    • Improved Scripting: GRUB2 uses a more powerful and flexible scripting language for its configuration.
    • Support for More Filesystems: GRUB2 can boot from a wider range of filesystems, including Btrfs and LVM.
    • Graphical Boot Menu: GRUB2 supports graphical boot menus, providing a more user-friendly boot experience.
    • UEFI Support: GRUB2 improved on support for UEFI (Unified Extensible Firmware Interface), becoming crucial for newer hardware.

  6. Firewalld: firewalld replaced iptables as the default firewall management tool. firewalld offers a more dynamic and user-friendly approach to firewall configuration:

    • Dynamic Firewall Rules: firewalld allows you to change firewall rules without restarting the firewall service, making it more responsive to changing network conditions.
    • Zones: firewalld uses zones to define different security levels for different network interfaces or connections.
    • Services: firewalld allows you to manage firewall rules based on predefined services, simplifying configuration.
    • Rich Language: firewalld provides a rich language for defining complex firewall rules.

  7. Default MariaDB instead of MySQL: CentOS 7 switched to MariaDB as the default database server, replacing MySQL. MariaDB is a community-developed fork of MySQL, offering compatibility and improved performance in many cases.

  8. Updated Software Packages: CentOS 7 included updated versions of many core software packages, such as:

    • GCC 4.8.5: The GNU Compiler Collection was updated, providing support for newer C/C++ standards and optimizations.
    • Glibc 2.17: The GNU C Library was updated, providing essential system functions and APIs.
    • OpenSSL 1.0.1e: The OpenSSL library, crucial for secure communication, was updated. (Note: This version later had security vulnerabilities, highlighting the importance of regular system updates).
    • Python 2.7.5: Python 2.7.5 was the default python version.

  9. chrony for time synchronization: CentOS 7 uses chrony by default instead of ntpd for time synchronization. chrony generally provides more accurate and faster time synchronization, particularly on systems with intermittent network connectivity.

  10. LVM Thin Provisioning: CentOS 7 offers the option for thin provisioning with Logical Volume Manager. This enables storage volumes that appear larger than the physical storage they occupy which provides a cost-effective storage solution.

Conclusion:

CentOS 7 was a landmark release that brought significant modernization to the CentOS platform. The adoption of systemd, XFS, and Docker, along with the updated kernel and core packages, transformed CentOS into a more powerful, efficient, and modern operating system. Its long-term support and stability made it a popular choice for enterprise deployments, and its legacy continues to influence subsequent CentOS and RHEL releases. While its end-of-life is approaching, understanding the key features of CentOS 7 is crucial for anyone working with Linux systems, especially those migrating to newer distributions.

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