1. Chapter 4 Booting and Shutdown
CSNB113 SYSTEM ADMINISTRATION
College of Information Technology
Universiti Tenaga Nasional (UNITEN)
SN 2017

2. Objectives
Understand the concept of run levels and their role in startup and shutdown operations
SN 2014

3. Introduction
Startup and shutdown procedures are controlled by automated shell scripts
System administrator needs to know that exact sequence of steps the system follows during the two events – able to fix if things do go wrong
SN 2017

4. Booting Step 1 Step 2 Step 3 Step 4 PID1: Process-id 1
Machine is powered on
Step 1
System looks for all peripherals
Step 2
Follow a series of steps  lead to the loading of kernel into memory
Step 3
Kernel spawns init (PID1), followed by other processes
Step 4
PID1: Process-id 1
SN 2017

5. init init process: second process of the system
Behavioral pattern of init for three vital reasons:
Maintains the system at a specific run level (state) and decides which processes to run for each run level
Parent of all system daemons (process) that keep running all the time
Spawns a getty process at every terminal so that users can log in – parent of all shell
SN 2017

6. Run level Indicated by a single digit (0 to 6), or an s or S Run level
Description
System shutdown 1
System administration mode (local file system mounted) 2
Multiuser mode (NFS not available) 3
Full multiuser mode 5
The graphical environment mode in Linux 6
Shutdown and reboot mode
s or S
Single-user mode (file systems mounted)
SN 2017

7. init : Run level init state 1 or S init state 2, 3, or 5
Machine is powered on
init state 2, 3, or 5
Multiuser mode
init state 0 or 6
System is shutdown
System administrator has the freedom to use the init command to move the system to any run level. Example:
# init 1
SN 2017

8. Display run level who -r surizal@sn010101-scnb113 :~$ who –r
Example:
Run level 2: ___________ mode
SN 2017

9. Shutdown shutdown command: shut the machine down
Notifies users with wall about the system going down with a directive log out
Activities during shutting down (sleeping for one minute):
Sends signals to all running process – normally terminate the process
Log off and kill remaining processes
Unmounts all secondary file systems – unmount command
Write all memory-resident data to disk – sync command
Notifies users to reboot or switch off
SN 2017

10. Shutdown - Ubuntu
P option: overrides the default sleeping time of one minute
r option: shutdown and restart/reboot
# shutdown –P 2
Powers down machine after 2 minutes
# shutdown –P 0
Immediate shutdown
# shutdown –r 0
Immediate shut down and reboot
SN 2017

11. References
Das, S. (2012). Your UNIX/LINUX The Ultimate Guide: Third Edition. McGraw-Hill
Hahn, H. (2008). Harley Hahn's Guide to Unix and Linux. California: McGraw-Hill Higher Education
SN 2014