Linux Operating System Fundamentals and Architecture

Linux Operating System Fundamentals

1. Licensing

Linux distributions are distributed under the GNU General Public License.

2. Understanding Swap Memory

Swap (virtual memory) is used to load programs when RAM reaches its capacity, preventing system saturation.

3. Logical Volume Management (LVM)

LVM allows for the creation of logical volumes with adjustable sizes.

• Advantages: Ability to split or merge partitions dynamically.

4. Benefits of Linux

• Multitasking: Run multiple programs simultaneously.
• Multiuser: Multiple users can access the same machine at the same time.
• Memory Protection: Isolates processes so one cannot crash the entire system.

5. Default File Systems

• EXT2: Supports standard Unix file types (regular files, directories, symlinks).
• EXT3: Improves upon EXT2 by significantly reducing recovery time after a system failure.

6. RAID 0 vs. RAID 5

Each RAID level offers a specific balance of fault tolerance, performance, and cost. No level is inherently better; each is suited for specific environments.

• RAID 0: Offers the highest disk transfer speed but lacks fault tolerance.
• RAID 5: Provides a balance of speed and security through independent access with distributed parity. It is especially suited for multi-user environments.

7. GRUB Boot Manager

GRUB is a boot manager that allows users to select the OS to boot and pass arguments to the kernel.

• Recognizes several executable formats.
• Supports multiboot features by loading multiple modules.
• Includes a flexible command interface accessible from the menu.
• Automatically detects installed RAM.

8. Execution Levels (Runlevels)

There are 6 defined execution levels reserved for system management.

9. Single-User Runlevel

This level is used for system maintenance.

• Accesses the system without network services.
• The user operates with root privileges.

10. General Operating System Characteristics

• Task Administration: Single-tasking or multitasking.
• User Administration: Single-user or multiuser.
• Distributed: Designed to share resources across systems.
• Open Source: All source code is available, including the kernel.