Linux Architecture

Overview

1

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

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

System Structure-2

4

Sockets VFS Vmem ProcessControl

NFSTCP, IP, etc

Proc, sysfs

File sysmmap

MM

Process memory

IPC

System Structure

5

Kernel+

h/w related code

System Call Interface

User mode space

Device drivers

Kernel mode space

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

6

Directory structure

7

user

hom e

bin sbin lib

usr etc bin sbin

/

• /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

8