TODO

• https://bottomupcs.com/ch01s03.html
• https://homepages.uc.edu/~thomam/Intro_Unix_Text/TOC.html
• https://dsf.berkeley.edu/cs262/FFS.pdf
• https://ops.tips/blog/what-is-slash-proc/ and Proc FS
• https://www.cs.fsu.edu/~baker/opsys/notes/unixfiles.html
• Looks good https://www.cs.fsu.edu/~baker/opsys/notes/
• https://users.cs.jmu.edu/bernstdh/web/common/lectures/summary_unix_file-descriptors.php

Components

File system

Proc

Julia Evans

fid

Commands

Boot Process

• Step 1 - When we turn on the power, BIOS (Basic Input/Output System) or UEFI (Unified Extensible Firmware Interface) firmware is loaded from non-volatile memory, and executes POST (Power On Self Test).

• Step 2 - BIOS/UEFI detects the devices connected to the system, including CPU, RAM, and storage.

• Step 3 - Choose a booting device to boot the OS from. This can be the hard drive, the network server, or CD ROM.

• Step 4 - BIOS/UEFI runs the boot loader (GRUB - Grand Unified Bootloader), which provides a menu to choose the OS or the kernel functions.

• Step 5 - After the kernel is ready, we now switch to the user space. The kernel starts up systemd as the first user-space process, which manages the processes and services, probes all remaining hardware, mounts filesystems, and runs a desktop environment.

• Step 6 - systemd activates the default. target unit by default when the system boots. Other analysis units are executed as well.

• Step 7 - The system runs a set of startup scripts and configure the environment.

• Step 8 - The users are presented with a login window. The system is now ready.

Network

Performance Observability Tools

Ref: https://www.brendangregg.com/linuxperf.html