The Linux system initializes with Uboot loading the kernel, which then initializes and calls init. Init runs startup scripts like run_flphone.sh, which launches the X Windows server and window manager. The system structure has a microkernel that manages interprocess communication and memory, along with autonomous processes for filesystems, networking, device drivers, and more. Above the kernel runs the windowing system, compilers, shells, and utilities. Key system directories include /bin, /sbin, and /lib for essential binaries and libraries, /usr/bin and /usr/sbin for non-essential binaries, /etc for configuration files, and /home for user directories. Processes transition between new, ready,

1. Linux Architecture
Overview
1

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
2

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
3

4. System Structure
4
Kernel
+
h/w related code
System Call Interface
User mode space
Device
drivers
Kernel mode space

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

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

7. Directory structure
7
user
home
bin sbin lib
usr etc bin sbin
/

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
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9. © 2004, D. J. Foreman 9
Basic Transitions
New
Ready
Running
Waiting
Blocking I/O
or Wait
requested
Dispatched
by system
Terminated
Exit request
Interrupt/Signal
# ready queues
may be >1

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

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