1. Linux Architecture
Overview

2. Initialization Uboot – hardware init, loads kernel
Kernel – remaining initialization, calls “init”
Init – 1st process, executes startup script
/etc/init.d/rcS
Run_flphone.sh – startup script
Nano-X – the X-Windows server
Nanowm – sets bg image

3. System Structure MicroKernel – minimal functionality
Interprocess communication (IPC)
Memory management
Autonomous processes & co-routines
VFS
Network stack
Process manager
Device drivers
Non-kernel
windowing system
compiler
shells
Editors
utilities

4. System Structure-2 VFS Vmem mmap Proc, sysfs TCP, IP, etc NFS MM IPC
Sockets
Process Control
VFS
Vmem
mmap
Proc, sysfs
TCP, IP, etc
Process memory
NFS
File sys MM
IPC

5. System Structure User mode space Kernel mode space Kernel +
System Call Interface
Device drivers
Kernel +
h/w related code

6. Structural Problems Erroneous co-routines can block system
Formal interfaces slow down system

7. Directory structure

8. /bin Essential user command binaries that need to be available also in single user mode.
/sbin Essential system binaries (e.g. init, insmod, ifup)
/lib Libraries for the binaries in /bin and /sbin
/usr/bin Non-essential user command binaries that are not needed in single user mode
/usr/sbin Non-essential system binaries (e.g. daemons for network-services)
/usr/lib Libraries for the binaries in /usr/bin and /usr/sbin
/etc Host-specific system-wide configuration files
/dev Device files
/home User home directories (optional)
/proc Virtual file system documenting kernel and process status as text files