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

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

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

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

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

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

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

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

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

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

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