UNIX Startup and Shutdown CSCI N321 – System and Network Administration Copyright © 2000, 2010 by Scott Orr and the Trustees of Indiana University

Section Overview Bootstrapping Startup Scripts and Run Levels Boot Configuration and Troubleshooting System Shutdown

References CQU COIT13146 System Administration Course Textbook  Chapter 13 Chapter 13 Lectures  2002 # #12

Monolithic Kernels Hardware Device Drivers, Dispatcher, … Scheduler, Virtual Memory IPC, File System VFS Application Source: KernelMode UserMode

Microkernels Hardware Basic IPC, Virtual Memory, Scheduling ApplicationIPC Source: KernelMode UserMode UNIXServer DeviceDriversFileServer Application

Bootstrapping Starting the system Process of loading kernel into memory Boot Modes Normal Single User/Safe Mode Rescue (on CD)

RedHat Boot Process BIOS LoginShell GRUB /etc/inittab Source: LinuxKernelinit /etc/rc.d/rc.sysinit/etc/rc.d/rc RL Specific /etc/inittab/etc/rc.d/rc3.d/etc/rc.d/rc5.d

Fedora Boot Process BIOS LoginShell GRUB /etc/inittab Source: LinuxKernelinit /etc/init/*.conf RL Specific /etc/rc.d/rc3.d/etc/rc.d/rc5.d

Boot Process Power On Self Tests (POST) Run Boot Loader(s) Load & initialize kernel Detect & configure devices Fork system processes (Stop if Single User mode) Run startup scripts Start multiuser operations

Boot Loader ROM loads Master Boot program from disk Primary Bootloader – Basic I/O, Program Loading 2 nd Boot Loader finds/loads kernel Checks available memory Initializes kernel internal data structures NTLDR – Microsoft Boot Loader GRand Unified Bootloader (GRUB) Can boot multiple OS Boot options can be edited at boot

/etc/grub.conf default=1 timeout=10 splashimage=(hd0,5)/boot/grub/splash.xpm.gz password –-md5 $1$0UwMq/$PeT.7qUpTeC29jc6k3pMv/ title Fedora Core - N321 ( _FC4) root (hd0,5) kernel /boot/vmlinuz _FC4 ro root=LABEL=/1 rhgb quiet initrd /boot/initrd _FC4.img title Windows XP rootnoverify (hd0,0) chainloader +1 title Red Hat Enterprise WS ( EL) rootnoverify (hd0,4) kernel /boot/vmlinuz EL ro root=LABEL=/ rhgb quiet initrd /boot/initrd EL.img

System Processes BSD Systems swapper – PID 0 init – PID 1 pagedaemon – PID 2 AT&T SVR4 sched – PID 0 (invisible under RedHat) init – PID 1 /etc/inittab

Startup Scripts Hostname Timezone Check the hard drives Mount the hard drives Remove files from /tmp Configure network interfaces Start daemons and network services

BSD /etc/rc* Scripts /etc/rc Master script Executes supplemental scripts Example supplemental scripts (freeBSD) /etc/defaults/rc.conf /etc/rc.conf /etc/rc.conf.local

/etc/inittab Initializes system for use Format: id:rl:action:process id : uniquely identifies entry rl : Run level entry applies to action : How to execute process process : process command line Ex: Setting the default Runlevel: id:3:initdefault:

Startup Run Levels RedHatMode 1 (S)Single user 2Multiuser (no networking) 3Full Multiuser 4Unused 5X11 6Reboot 0Halt

/etc/init/*.conf directives exec script start on stop on task respawn See man 5 init for more

“Events” control-alt-delete power-status-changed startup runlevel started stopped

Virtual Consoles Started in /etc/init/start-ttys.conf tty restarts in /etc/init/tty.conf Example: /etc/init.d/tty.conf: # tty - getty # # This service maintains a getty on the sepcified device. stop on runlevel [016] respawn instance $TTY exec /sbin/mingetty $TTY

Started in /etc/event.d/rc[0-6,S] : Example (rc3): start on runlevel [ ] stop on runlevel [!$RUNLEVEL] task export RUNLEVEL console output exec /etc/rc.d/rc $RUNLEVEL Strarting/Stopping Run Levels

Run Level Scripts Actual scripts - /etc/rc.d/init.d/ /etc/rc.d/rc#.d/ Symbolic links to /etc/init.d scripts S## - Start scripts K## - Stop scripts /etc/sysconfig/ - script configuration files chkconfig on|off service start|stop|restart

Startup Messages Displayed to console RedHat – daemon [ ok ] /bin/dmesg History of boot messages Convenient to search RedHat allows for interactive setup (“i”)

System Shutdown Turn off power – BAD!!! Reboot reboot shutdown –r Halting the system halt shutdown –h Changing the Run Level telinit shutdown –i

When to Shutdown Failures Maintenance and Upgrades Regularly Scheduled Housecleaning Window for Maintenance/Upgrades User Notification /etc/motd Support web pages