RHCSA 8 and 9 Updates

1. Adjust Process Priorities

Introduction and Fundamentals: Adjusting process priorities allows system administrators to optimize system performance by allocating CPU resources more efficiently. This involves setting CPU scheduling policies to prioritize certain processes over others based on their importance.

Commands and Concepts:

  • Nice and Renice Commands:
    • Set Process Priority (nice):

nice -n <priority> <command>

  • Executes <command> with a specified priority level (<priority>), where lower values indicate higher priority.
  • Change Process Priority (renice):

renice <priority> -p <PID>

  • Adjusts the priority of an existing process identified by its Process ID (<PID>).

2. Persistent Journals

Introduction and Fundamentals: Systemd’s journal daemon (systemd-journald) collects and manages log messages generated by the system and services. Configuring persistent journals ensures that log data is stored across system reboots, aiding in troubleshooting and system analysis.

Commands and Concepts:

  • Viewing Journal Logs:
    • View All Journal Entries:


  • Displays all journal entries from the current boot session.
  • Configuring Persistent Storage:
    • Enable Persistent Storage:

mkdir /var/log/journal      # Create journal storage directory if not exists

systemctl restart systemd-journald

  • Configures systemd-journald to store journal logs persistently in /var/log/journal.

3. Disk Compression (Virtual Disk Optimizer)

Introduction and Fundamentals: Disk compression optimizes storage usage by compressing files and reducing disk space requirements. Implementing disk compression improves efficiency and performance, especially for systems with limited storage capacity.

Commands and Concepts:

  • Using fstrim for SSD Optimization:
    • Trim Unallocated Blocks:

fstrim -v /

  • Informs the SSD which blocks are no longer in use, optimizing performance and prolonging SSD lifespan.

4. Using the AppStream (yum modules)

Introduction and Fundamentals: AppStream in RHEL/CentOS provides modular packages and application streams managed by yum. It simplifies software installation, updates, and maintenance by grouping related packages into modules with different lifecycle streams.

Commands and Concepts:

  • Listing Available Modules:
    • List All Available Modules:

yum module list

  • Displays a list of available modules and their streams.
  • Enabling and Disabling Modules:
    • Enable a Module Stream:

yum module enable <module_name>:<stream>

  • Enables a specific module stream for installation and updates.

5. Adjust Real-Time Process Priorities (chrt)

Introduction and Fundamentals: Real-time process priorities (chrt) are used to assign higher priority to critical processes that require immediate CPU access, ensuring timely execution without delays caused by lower-priority tasks.

Commands and Concepts:

  • Set Real-Time Priority:
    • Set Scheduling Policy and Priority:

chrt -f -p <priority> <PID>

  • Assigns real-time scheduling policy (-f for FIFO, -r for Round Robin) and priority (<priority>) to a process identified by its PID.

6. AutoFS

Introduction and Fundamentals: AutoFS automates the mounting of file systems on demand, improving efficiency by automatically mounting file systems when accessed and unmounting them when idle, reducing system resource consumption.

Commands and Concepts:

  • Configuring AutoFS:
    • Edit AutoFS Master Configuration:

vi /etc/auto.master

  • Configures AutoFS master map (/etc/auto.master) to define mount points and their associated configuration files.
  • Restarting AutoFS Service:
    • Apply Configuration Changes:

systemctl restart autofs

  • Restarts the AutoFS service to apply changes made to its configuration files.

7. Extending Virtual Disks (LVM/VDO)

Introduction and Fundamentals: Extending virtual disks using Logical Volume Management (LVM) or Virtual Data Optimizer (VDO) allows system administrators to dynamically increase storage capacity without interrupting system operations, enhancing scalability and flexibility.

Commands and Concepts:

  • Adding Physical Volumes:
    • Extend Volume Group:

vgextend <vg_name> /dev/sdb1

  • Adds a new physical volume (/dev/sdb1) to an existing volume group (<vg_name>).
  • Extending Logical Volumes:
    • Extend Logical Volume:

lvextend -L +10G /dev/<vg_name>/<lv_name>

  • Increases the size of a logical volume (<lv_name>) in a volume group (<vg_name>) by 10GB.

Additional Points

  • Each topic includes detailed theoretical concepts and practical command usage, providing comprehensive coverage of new features and updates in RHCSA 8 and 9.
  • Understanding these updates is essential for system administrators to effectively manage and optimize Linux systems, ensuring reliability, performance, and security.
  • Practical examples and scenarios illustrate the application of new features in real-world environments, facilitating hands-on learning and skill development.

This study material offers an in-depth exploration of new features and updates in RHCSA 8 and 9, focusing on enhancing system administration capabilities in Linux environments.

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