1. History
   1. aka
      1. GNU/LINUX
         1. Reason
            1. Linux
            2. is
            3. Kernel
            4. GNU-software
            5. make
            6. Linux
            7. useful
            8. exists
            9. outside
            10. the Kernel
            11. range
            12. Windowing system
            13. eg. X11
            14. Compiler
            15. Shells
            16. Dev tools
            17. Editors
            18. Utilities
            19. others!
   2. 1960
      1. MIT and other companies
         1. developed
            1. Multics (Multiplexed Information and Computing Services)
   3. 1970
      1. AT&T
         1. dropped out
         2. developed
            1. own
            2. OS (Unics)
            3. plus
            4. C-language
   4. 1990
      1. Andrew Tanenbaum
         1. created
            1. MINIX(minimal UNIX)
            2. ran on
            3. small PC
   5. Early 1990s
      1. Linus Torvalds
         1. developed
            1. Linux
   6. Linux
      1. adopted
         1. GNU GPL
            1. which allowed
            2. GCC
            3. shells
2. Kernel
   1. Components
      1. Linux Kernel Components
         1. Process Manager
            1. focused on
            2. execution of
            3. the processes
            4. provides
            5. an API
            6. through SCI
            7. to
            8. create new process
            9. through
            10. fork
            11. exec
            12. POSIX functions
            13. stop process
            14. through
            15. kill
            16. exit
            17. POSIX functions
            18. communicate & synchronise b/w processes
            19. through
            20. signal
            21. POSIX mechanisms
            22. implements
            23. a scheduling Algorithm
            24. to
            25. share CPU
            26. between
            27. active threads
         2. Virtual File System+FileSystem+Buffer Cache
            1. VFS
            2. is
            3. interface abstraction
            4. for file systems
            5. a switching layer
            6. b/w
            7. SCI
            8. and
            9. the file system supported by kernel
            10. Buffer Cache
            11. optimizes
            12. file-system
            13. access to
            14. devices
            15. is
            16. independent
            17. of any
            18. particular
            19. filesystem
            20. source
            21. ./linux/fs
         3. Memory Management
            1. source
            2. ./linux/mm
            3. manages
            4. memory
            5. in
            6. pages
            7. mostly
            8. 4KB
         4. Network Stack
            1. Socket-layer
            2. is
            3. UI
            4. to
            5. a variety of
            6. networking
            7. protocols
            8. the standard
            9. api
            10. to the
            11. networking
            12. subsystem
            13. invoked
            14. through
            15. SCI
            16. protocol-independent
            17. source
            18. ./linux/net
         5. Device Drivers
            1. constitute
            2. major
            3. part of
            4. Kernel
            5. is a
            6. sub-directory
            7. divided by
            8. various
            9. devices
            10. source
            11. ./linux/drivers
         6. Arch-dependent Code
            1. source
            2. ./linux/arch
            3. aka BSP
   2. Interesting features
      1. supports
         1. numerous
            1. Networking
            2. Protocols
            3. TCP/IP
            4. GbE
            5. SCTP(Stream Control Transmission Protocol)
      2. dynamic kernel
         1. as
            1. SW components/modules
            2. can be
            3. added/removed
            4. on the fly
      3. recently
         1. used as
            1. hypervisor
            2. ie. an OS
            3. for
            4. other OSs
         2. a modification
            1. called
            2. KVM (Kernel-based VM)
            3. allows
            4. this
3. Architecture
   1. Linux Architecture - Two levels
      1. User app
      2. glibc
         1. GNU C library
            1. is
            2. a wrapper around the system calls of the Linux kernel
            3. POSIX compliant
            4. alternatives
            5. Newlib
            6. uClibc
            7. Bionic
            8. used in adnriod
            9. based on libc from BSD
            10. Klibc
            11. and others
         2. provides
            1. system call interface (SCI)
            2. connects to Kernel
            3. provides
            4. mechanism
            5. to transition b/w user and kernel space
            6. implements
            7. basic
            8. function
            9. calls
            10. from
            11. User space
            12. Kernel space
            13. as
            14. read
            15. write
            16. open
            17. etc.
            18. can be arch dependant
      3. Kernel
         1. Two parts
            1. Architecture-independent code
            2. Architecture-dependant code
            3. aka
            4. Board Support Package
            5. Processor & Platform specific code