BIOS, Boot Options, USB Permissions, and Cooling

BIOS (Basic Input Output System):
- Older system, limited to 16-bit.
- Text-only interface.
- Navigated using the keyboard only.
- Could not support drives larger than 2 terabytes.
- Slower boot times.
- No mouse support.
UEFI (Unified Extensible Firmware Interface):
- 64-bit operation.
- GUI (Graphical User Interface) support.
- Supports drives over 2 terabytes.
- Full network functionality during boot.
- Supports secure boot.
Accessing BIOS/UEFI Settings:
- Restart the computer.
- Press the designated key (usually F2, but varies by motherboard).

Boot Sequence/Boot Device Priority/Boot Order:
- Determines the order in which the computer tries to load the operating system from different devices.
- Default setting: loads from the hard drive (where the operating system usually resides).
Installing Windows from USB:
- When installing a new operating system, the boot order needs to be changed to prioritize the USB drive.
- After installation, the boot order MUST be changed back to the hard drive to avoid boot errors.
Boot Device Not Found Error:
- Often indicates an incorrect boot order setting in the BIOS/UEFI.
- A common test scenario involves a newly installed hard drive and the computer failing to boot.
Getting Windows on a USB Drive:
- Download the Windows installation media onto a formatted USB drive.
- The USB drive becomes the installation or recovery media.
Common Boot Devices:
- Hard drive or solid-state drive (SSD).
- Optical drive (CDs, DVDs - older method).
- USB drive (common for installation).
- Pixie Boot (Preboot Execution Environment).

Explanation:
- Allows booting from a network.
- Used in businesses with thin clients.
Thin Clients:
- Small computers with minimal processing power and storage.
- Rely on a server for most of the processing and data storage.
- Connect to the LAN (Local Area Network).
Benefits:
- Cost-effective (cheaper computers).
- Centralized resource management.
Functionality:
- The operating system (e.g., Windows) resides on a server.
- The thin client boots from the network, accessing the OS from the server.

Control via BIOS:
- The BIOS/UEFI firmware can control USB ports.
- Unused USB ports can be disabled.
Benefits of Disabling USB Ports:
- Improved boot speed (slightly).
- Reduced power usage (slightly).
- Increased security (main reason).
Security Hardening:
- Disabling unnecessary USB ports is a security measure.
- Principle of least privilege: grant only the minimum access needed.
USB Security Risks:
- Malicious programs can be loaded via USB drives.
- Hacking devices like "rubber duckies" can be disguised as USB drives.
- Unauthorized personnel could insert infected USBs.

Importance of Cooling:
- Essential for preventing damage to computer components.
- Avoids thermal throttling (slowing down due to overheating).
- Prevents system shutdown to protect against damage.
Maintenance:
- Keep fans clean.
- Clear intake ports for proper airflow.
Temperature Monitoring:
- Maximum temperature for a computer is around $105$ degrees Celsius at which point it will shut down to prevent component damage.
- Optimal temperature for data centers is around $72$ degrees Fahrenheit.
Fan Control via BIOS:
- System settings allow for balanced, cool, or quiet modes.
- Fanless operation is possible with passive cooling systems (rare).
Temperature Monitoring Methods:
- Manual monitoring: Restart the computer and check in the BIOS.
- Third-party monitoring software: Provides real-time temperature monitoring through an app.
- Visual indicators: Some systems use lights that change color based on temperature (e.g., green = normal, yellow = warning, red = critical).