Wednesday, August 23, 2023

Devops topics to be covered

  1. Linux Booting Process: The Linux booting process involves several stages: BIOS/UEFI initializes hardware, boot loader (GRUB) loads the kernel, kernel initializes hardware and mounts the root filesystem, and init/systemd starts essential processes.

  2. Systemd: Systemd is an initialization system and service manager in Linux. It's responsible for starting and managing system services, handling daemons, and managing system resources.

  3. Web Servers (Apache, Nginx, Tomcat): Web servers handle incoming requests and serve web content. Apache, Nginx, and Tomcat are popular choices. They listen on specific ports, process requests, and serve web pages, applications, or servlets.

  4. Linux Processes: Linux processes are running instances of programs. Each has a unique process ID (PID) and resources. They can communicate, spawn child processes, and be managed by signals.

  5. HTTP Proxies: HTTP proxies act as intermediaries between clients and servers, forwarding requests and responses. They can be used for caching, load balancing, security, and content filtering.

  6. SSH (Secure Shell): SSH is a secure protocol for remote access and secure communication. It uses encryption to ensure confidentiality and integrity of data transmitted over the network.

  7. File Systems: File systems manage how data is stored and organized on storage devices. Examples include ext4, XFS, and Btrfs, each with different features and optimizations.

  8. Volumes in Linux: Volumes are a way to manage and organize storage. In Linux, LVM (Logical Volume Management) provides flexibility in managing disks and volumes.

  9. System Logging, Monitoring, Troubleshooting: System logs store information about system events. Monitoring tools like Prometheus, Grafana help track system performance. Troubleshooting involves identifying and fixing issues by analyzing logs and metrics.

  10. Important Protocols (SSL, TLS, TCP, UDP, FTP, SFTP, SCP, SSH): SSL/TLS provide secure communication. TCP ensures reliable data transfer, while UDP is faster but less reliable. FTP, SFTP, SCP are used for file transfer. SSH provides secure remote access.

  11. Managing Services and Creating Your Own: Services are background processes. Systemd manages services. You can create your own services by writing unit files with configuration and execution instructions.

  12. Load Balancer vs. Reverse Proxy: A load balancer distributes traffic across multiple servers. A reverse proxy handles requests on behalf of servers and can provide features like SSL termination and caching.

  13. Optimizing Linux Performance: Optimize by tuning kernel parameters, managing resources efficiently, using caching mechanisms, and monitoring performance metrics.

  14. Database Setup and Management (PostgreSQL): Setting up a database involves installing, configuring, and managing a database server. PostgreSQL is a popular open-source relational database.

  15. Troubleshooting by Breaking Things: Experimenting with controlled failures helps you understand how systems behave under stress. Learn to diagnose and fix issues systematically.

Here are some example commands and code snippets related to the topics you mentioned:

  1. Linux Booting Process:

    • dmesg command to view kernel messages.
    • systemctl commands to manage services.
  2. Systemd:

    • systemctl start serviceName to start a service.
    • systemctl enable serviceName to enable a service on boot.
  3. Web Servers (Nginx):

    • Install Nginx: sudo apt-get install nginx.
    • Start Nginx: sudo systemctl start nginx.
    • Configuration file: /etc/nginx/nginx.conf.
  4. Linux Processes:

    • ps aux to list all running processes.
    • kill PID to terminate a process by its PID.
  5. HTTP Proxies:

    • Configure Nginx as a reverse proxy: Example nginx.conf:
      arduino
      server { location / { proxy_pass http://backend_server; } }
  6. SSH:

    • Connect to a remote server: ssh username@hostname.
  7. File Systems:

    • Create an ext4 filesystem: sudo mkfs.ext4 /dev/sdX.
  8. Volumes in Linux (LVM):

    • Create a physical volume: sudo pvcreate /dev/sdX.
    • Create a volume group: sudo vgcreate vg_name /dev/sdX.
    • Create a logical volume: sudo lvcreate -L size -n lv_name vg_name.
  9. System Logging, Monitoring, Troubleshooting:

    • View system logs: cat /var/log/syslog.
    • Monitor CPU usage: top or htop.
    • Troubleshoot network issues: ping, traceroute.
  10. Important Protocols (SSH):

    • Generate SSH key pair: ssh-keygen.
    • Copy SSH public key to remote server: ssh-copy-id username@hostname.
  11. Managing Services and Creating Your Own (Systemd):

    • Create a systemd service unit file: /etc/systemd/system/serviceName.service.
    • Example service unit file:
      scss
      [Unit] Description=My Custom Service [Service] ExecStart=/path/to/your/command Restart=always [Install] WantedBy=default.target
  12. Load Balancer (Nginx):

    • Example Nginx configuration for load balancing:
      arduino
      upstream backend { server backend1; server backend2; } server { location / { proxy_pass http://backend; } }
  13. Optimizing Linux Performance:

    • Tune TCP settings: sysctl commands.
    • Monitor disk I/O: iostat -x.
  14. Database Management (PostgreSQL):

    • Install PostgreSQL: sudo apt-get install postgresql.
    • Access PostgreSQL prompt: sudo -u postgres psql.
    • Create a database: CREATE DATABASE dbname;.
  15. Troubleshooting by Breaking Things:

    • Simulate network issues: tc command for traffic control.
    • Cause high CPU load: stress command.

Remember to replace placeholders like serviceName, backend_server, username, hostname, etc., with your actual values. These examples should help you get started with practical implementations in your learning journey.