Skip to content
nexarq Docs

Operating Systems & Linux Fundamentals

Linux in the Cloud Context

Section titled “Linux in the Cloud Context”

Linux is the de facto operating system for cloud infrastructure, edge computing, and containerization. Understanding its core mechanisms is essential for troubleshooting and performance tuning.

Kernel Space vs. User Space

Section titled “Kernel Space vs. User Space”
  • Kernel Space: Privileged mode where the kernel executes. Manages hardware resources (CPU, memory, I/O) and provides system calls. The Linux Kernel Documentation.
  • User Space: Restricted mode where applications (Nginx, Node.js) run. They must use System Calls (e.g., read(), write(), fork()) to request kernel services.
  • Context Switching: The CPU switching between user and kernel mode. High context switching rates can indicate performance bottlenecks.

Process Management

Section titled “Process Management”
  • PID (Process ID): Unique identifier for every running process. Process Management in Linux (Red Hat).
  • Signals: Inter-process communication.
    • SIGTERM (15): Graceful termination request.
    • SIGKILL (9): Immediate forced termination (cannot be caught).
    • SIGHUP (1): Reload configuration (common in daemons like Nginx).
  • Load Average: The average number of processes waiting for CPU time over 1, 5, and 15 minutes. A load > number of cores implies saturation.

File Descriptors & Permissions

Section titled “File Descriptors & Permissions”
  • Everything is a File: In Linux, sockets, pipes, and devices are treated as files.
  • File Descriptors (FD): Integers representing open files/sockets. High-concurrency servers (like Nginx) require high ulimit -n values to handle thousands of connections. What are File Descriptors? (DigitalOcean).
  • Permissions (Octal/Symbolic):
    • chmod 755 (rwxr-xr-x): Owner has full access; Group/Others can read/execute.
    • chmod 600 (rw-------): Only owner can read/write (standard for private keys).
    • chown user:group: Change ownership.

Why Linux for Edge?

Section titled “Why Linux for Edge?”
  • Performance: Lightweight kernel, efficient TCP/IP stack implementation.
  • eBPF (Extended Berkeley Packet Filter): Allows running sandboxed programs in the kernel without changing source code. Used extensively by Cloudflare for high-performance packet filtering and observability.