1. Linux Start Sequence Summary
CS7493

2. Linux Startup
The compressed version of the kernel is loaded into memory.
Look in /boot for kernel
uname –a will show the kernel version
The kernel expands and begins to run

3. Linux Startup The initrd process is loaded and begins to run
This process acts as a memory based file system before the actual HD is mounted.
Several special processes are started
Drivers are loaded for some hardware devices including the root file system.

4. Linux Startup The process init is started, PID = 1.
init reads the inittab file: /etc/inittab
inittab defines the boot level
The rc.sysinit script is run: /etc/rc.d/rc.sysinit
The rc script is run: /etc/rc.d/rc

5. Linux Startup
The rc script starts the services for the specified runlevel: rc 5
Runlevels
0 = shutdown
1 = single user mode
2= multi user mode
3 = level 2 + networking
5 = level 3 + X windows (for the GUI)
6 = restart

6. Linux Startup The startup directories and files are found in /etc
/etc/rc.d
rcN.d where n = the runlevel
rc.sysinit rc
/etc/init.d

7. Linux Startup
There are a series of symbolic links in the /etc/rc.d/rcN.d
The links are connected to the actual services started during the startup procedure.
KxxserviceName (kill service)
SxxserviceName (start service)
Where xx is a two digit field

8. Linux Startup
The actual startup script for anavailable service is in /etc/init.d
Create a link from /etc/rc.d/rcN.d to the desired service in /etc/ini.d, to start the service during boot.
Manual start of a service:
service serviceScriptName [start|stop|restart]

9. How to manually start a service
su – root
Enter the root password
cd /etc/init.d
service ./serviceScriptName start
Example:
service ./smb start
(starts Samba)

10. Stop a service Login as root cd /etc/init.d
service ./serviceScriptName stop