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Introduction to Red Hat Linux

Red Hat Enterprise Linux (RHEL) is a leading open-source operating system developed by Red Hat, Inc. It is designed for enterprise environments, offering stability, security, and robust support for mission-critical applications. RHEL is widely used in servers, cloud environments, and enterprise IT infrastructure.

History

• 1994: Red Hat Linux was first released as a commercial Linux distribution.
• 2002: Red Hat introduced Red Hat Enterprise Linux, focusing on enterprise-grade reliability.
• 2025: RHEL 9 is the latest major release, with RHEL 10 in development, offering advanced features like enhanced security and container support.

Key Features

• Stability: RHEL prioritizes long-term support (LTS) with a 10-year lifecycle per major release.
• Security: Features like SELinux (Security-Enhanced Linux), firewalld, and regular security patches.
• Performance: Optimized for high-performance computing, virtualization, and cloud deployments.
• Subscription Model: Provides access to updates, support, and certified software through Red Hat subscriptions.
• Ecosystem: Integrates with Red Hat OpenShift, Ansible, and other tools for DevOps and automation.

Installation

System Requirements

• Minimum:
  • 1.5 GB RAM
  • 20 GB disk space
  • 1 GHz processor
• Recommended:
  • 4 GB RAM or more
  • 40 GB+ disk space
  • Multi-core processor

Installation Steps

1. Download RHEL:
   • Obtain the RHEL ISO from the Red Hat Customer Portal (requires a subscription or developer account).
   • Alternatively, use a free developer subscription for non-production use.
2. Create Bootable Media:
   • Use tools like dd or Rufus to create a bootable USB drive.
   • Example command: sudo dd if=rhel-9.3-x86_64.iso of=/dev/sdX bs=4M status=progress
3. Boot and Install:
   • Boot from the USB or DVD.
   • Follow the Anaconda installer:
     • Select language and region.
     • Configure disk partitioning (manual or automatic).
     • Set up network settings.
     • Create a root password and user accounts.
4. Register System:
   • Post-installation, register with Red Hat Subscription Manager: subscription-manager register --username <username> --password <password>.
   • Attach a subscription: subscription-manager attach --auto.

System Administration

Package Management

RHEL uses DNF (Dandified YUM) for package management.

• Install a package: sudo dnf install <package-name>
• Update system: sudo dnf update
• Search for packages: sudo dnf search <keyword>
• Enable repositories: sudo subscription-manager repos --enable <repo-id>

User Management

• Add a user: sudo useradd -m <username>
• Set password: sudo passwd <username>
• Modify user: sudo usermod -aG <group> <username>
• Delete user: sudo userdel -r <username>

File System Management

• Check disk usage: df -h
• List mounted file systems: lsblk
• Manage partitions: Use fdisk or parted for disk partitioning.
• Configure LVM (Logical Volume Manager):
  • Create physical volume: pvcreate /dev/sdX
  • Create volume group: vgcreate <vg-name> /dev/sdX
  • Create logical volume: lvcreate -L <size> -n <lv-name> <vg-name>

Networking

• Configure network with nmcli:
  • List connections: nmcli connection show
  • Add a static IP: nmcli con mod <connection-name> ipv4.addresses 192.168.1.100/24 ipv4.gateway 192.168.1.1 ipv4.method manual
  • Activate connection: nmcli con up <connection-name>
• Manage firewall with firewalld:
  • Open a port: sudo firewall-cmd --add-port=80/tcp --permanent
  • Reload firewall: sudo firewall-cmd --reload

Security

• SELinux:
  • Check status: sestatus
  • Set mode (enforcing/permissive): sudo setenforce 0 (permissive) or sudo setenforce 1 (enforcing)
  • Modify policies: Use semanage and audit2allow for custom policies.
• Updates:
  • Apply security patches: sudo dnf update --security
• SSH:
  • Secure SSH: Edit /etc/ssh/sshd_config to disable root login (PermitRootLogin no) and change default port.
  • Restart SSH: sudo systemctl restart sshd

Advanced Features

Containers and Virtualization

• Podman: RHEL’s rootless container tool.
  • Run a container: podman run -it docker.io/library/centos bash
  • Build an image: podman build -t <image-name> .
• Virtualization: Use libvirt and virt-manager for managing VMs.
  • Install: sudo dnf install libvirt virt-manager
  • Start libvirt: sudo systemctl start libvirtd

Automation with Ansible

• Install Ansible: sudo dnf install ansible
• Create a playbook: ```yaml
  • name: Install Apache hosts: all tasks:
    • name: Install httpd dnf: name: httpd state: present ```
• Run playbook: ansible-playbook playbook.yml

Cloud Integration

• RHEL integrates with AWS, Azure, and Google Cloud.
• Use Red Hat OpenShift for container orchestration.
• Deploy RHEL images in cloud environments via Red Hat Cloud Access.

Troubleshooting

• Logs: Check /var/log for system logs (e.g., /var/log/messages or /var/log/secure).
• Systemd: Manage services with systemctl:
  • Check service status: systemctl status <service>
  • Restart service: systemctl restart <service>
• Performance: Use top, htop, or vmstat to monitor system performance.
• Network Issues: Use ping, traceroute, or nslookup for diagnostics.

Best Practices

• Regularly update the system to patch vulnerabilities.
• Use strong passwords and enforce SELinux policies.
• Back up critical data with tools like rsync or Red Hat’s rear.
• Monitor system health with tools like Cockpit (sudo dnf install cockpit).

Resources

• Red Hat Customer Portal
• RHEL Documentation
• Red Hat Developer Program
• Community forums like Red Hat Discuss

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