121. What is the key advantage of microkernel architecture?
- a) Higher reliability due to minimal kernel-space code
- b) Faster system calls
- c) Lower memory footprint than monolithic kernels
- d) Built-in device drivers
Answer: A - Moves most functionality (drivers, filesystems) to user-space servers (e.g., QNX, L4).
122. Which filesystem features copy-on-write (CoW) snapshots?
- a) ZFS and Btrfs
- b) ext4 and NTFS
- c) FAT32 and exFAT
- d) HFS+ and APFS
Answer: A - ZFS/Btrfs use CoW for atomic snapshots and data integrity.
123. What distinguishes an exokernel from other kernels?
- a) Provides low-level resource control to applications
- b) Includes pre-built filesystem drivers
- c) Uses monolithic design for performance
- d) Only runs interpreted languages
Answer: A - Exokernels (e.g., ExOS) expose hardware directly with library OSes.
124. Which component is NOT part of a microkernel?
- a) Device drivers
- b) Inter-process communication (IPC)
- c) Basic memory management
- d) CPU scheduling
Answer: A - Microkernels run drivers in user space for isolation.
125. What is "deduplication" in ZFS?
- a) Eliminates duplicate data blocks to save space
- b) Compresses filesystem metadata
- c) Mirrors data across disks
- d) Encrypts identical files together
Answer: A - Uses cryptographic hashes to identify redundant blocks.
126. Which OS pioneered capability-based security?
- a) KeyKOS
- b) Windows NT
- c) Linux
- d) macOS
Answer: A - KeyKOS (1980s) used tokens for object access control.
127. What is "FUSE" in Linux filesystems?
- a) Framework for user-space filesystem development
- b) Filesystem encryption tool
- c) Kernel module for FAT32
- d) Disk defragmentation utility
Answer: A - Allows non-root users to create filesystems (e.g., SSHFS).
128. Which feature is unique to Btrfs?
- a) Built-in RAID 5/6 support
- b) Journaling
- c) File permissions
- d) Symbolic links
Answer: A - Btrfs implements software RAID with parity checks.
129. What is "Unikernel" architecture?
- a) Single-address-space machine images for specific apps
- b) Microkernel with dynamic modules
- c) Monolithic kernel with GUI
- d) Cloud-only kernel
Answer: A - Compiles apps with minimal OS libs (e.g., MirageOS).
130. Which filesystem uses "write-anywhere" layout?
- a) ZFS
- b) ext4
- c) NTFS
- d) FAT32
Answer: A - ZFS writes data anywhere free space exists (no fixed locations).
131. What is "seL4" microkernel known for?
- a) Formally verified security
- b) Windows compatibility
- c) Built-in Android support
- d) GPU acceleration
Answer: A - Mathematically proven correctness (used in defense systems).
132. Which OS uses a hybrid kernel architecture?
- a) Windows NT
- b) Linux
- c) FreeBSD
- d) Minix
Answer: A - Windows combines monolithic (performance) + microkernel (HAL) traits.
133. What is "object-capability model" in OS design?
- a) Security via unforgeable access tokens
- b) OOP-based kernel programming
- c) File metadata system
- d) CPU cache management
Answer: A - Used in Genode, seL4 for least-privilege security.
134. Which ZFS feature prevents data corruption?
- a) Checksumming all data/metadata
- b) Automatic defragmentation
- c) In-memory compression
- d) File versioning
Answer: A - Detects silent data corruption via SHA-256/Edon-R.
135. What is "Library OS" paradigm?
- a) Apps bundle their own OS components as libraries
- b) Shared system-wide DLLs
- c) Kernel module repositories
- d) Package manager databases
Answer: A - Used in Unikernels/exokernels for specialization.
136. Which filesystem is case-sensitive on Windows?
- a) NTFS (when configured)
- b) FAT32
- c) exFAT
- d) ReFS
Answer: A - NTFS supports case-sensitivity via registry tweak.
137. What is "Plan 9" OS known for?
- a) Everything-is-a-file design
- b) First microkernel
- c) Cloud-native architecture
- d) Real-time capabilities
Answer: A - Extends Unix philosophy (networks, GUI as filesystems).
138. Which Btrfs feature helps recover corrupted files?
- a) Self-healing via checksums and replicas
- b) Automatic backup to cloud
- c) AI-based error correction
- d) Version control integration
Answer: A - Uses checksums + duplicate copies if RAID1 configured.
139. What is "NixOS" unique package management approach?
- a) Atomic upgrades with rollback via hashes
- b) Cloud-only packages
- c) Kernel-module autogen
- d) Blockchain verification
Answer: A - Each package version gets unique /nix/store path.
140. Which microkernel design minimizes context switches?
- a) L4's synchronous IPC
- b) Mach's message-passing
- c) QNX's priority inheritance
- d) Minix's layered servers
Answer: A - L4 maps IPC to register passing (no full context switch).