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

5. System Structure-2 System Calls get us to these functionalities VFS
Sockets
Process Control
VFS
Vmem
Process memory
Proc, sysfs
TCP, IP, etc
NFS
File sys’s
mmap
IPC MM
cache
Scheduler
Char dev’s
Block Devices
Device Module
Net Mgmt
Bus drivers
Net drivers
Char Drivers
Block Drivers
Memory access
Interrupts
swap
CPU circuits
Net adapter
Monitor, keybd
Disk controller
MMU, RAM
Bus controller

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

7. Directory structure

8. System directories
/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

9. Basic Transitions
# ready queues may be >1
© 2004, D. J. Foreman

10. Linux Process/Thread States
New
Ready
Running
Terminated
H/W
Any signal or event
Uninterruptible
Interruptible
waiting
Signal
Stopped*
* Requires action from another process
© 2004, D. J. Foreman

11. Windows Thread States Runnable Not runnable CPU scheduled New Ready
Running
preempted
Block requested
Block released
Waiting
Terminated
Page/stack wait
Not runnable
© 2004, D. J. Foreman