Unix System Administration Booting and Shutting Down Chapter

Unix System Administration Booting and Shutting Down Chapter 2

Six Steps to Better Footwear • Sock Shoe, Sock Shoe or Sock, Shoe? • • • Load and init the kernel Detect and config devices Create spontaneous processes Operator intervention System startup scripts Multi-user operation

Sock Shoe, Sock Shoe vs. Sock, Shoe • In case of fire. . . • Sock sock, shoe – Both feet will be kept warm • Sock Shoe, Sock Shoe – If raining, sock will get wet and cold – Sock shoe can hop around on one foot to stay dry

Colonel Kernel Here! Let’s Go. . . • Kernel is a program • Path is vendor dependent – Solaris - /kernel/genunix – Linux - depends, sometimes /vmlinuz, see /etc/lilo. conf • Two stage process – Boot loader read from disk or tape (vendor dependent) – Kernel loaded into memory

Let’s Probe Uranus Instead! • Kernel’s first chore • Detects and initializes devices built into kernel • Probes for additional device info and other devices • In Solaris, devices must be on and the system booted with boot -r to detect new devices

Processes That Start with a “(cheesy) Poof” • BSD Spontaneous Processes – swapper - process 0 – init - process 1 – pagedaemon - process 2 • ATT Spontaneous Processes – sched - process 0 – init - process 1 – various memory handlers (except on Solaris)

Hey, I Need a Little Help Here! • Single-user mode • Most modern version of Unix stop and ask for the “root” password before creating a Bourne shell with root privileges • Minimal services running and partitions mounted • Operator can run fsck, backups, etc. • CTRL-D to proceed to multi-user startup

Just follow the Script Please • Location, content and organization of the startup scripts varies by system • Two “standard” startup script methods exist. • BSD - /etc/rc, /etc/rc. boot, /etc/rc. single, /etc/rc. local • ATT - /etc/inittab, /etc/rc*. d/, /etc/init. d

I’ll Go This Way, You Go the BSD Way

Calling All Operators, How Does ATT Startup? • Run + /etc/inittab determines scripts to run • /etc/rc* scripts run programs that start with “S” in the /etc/rc*. d directories – foreach f in rc 2. d • run $f • /etc/rc*. d startup scripts are usually linked to a scripts in a common /etc/init. d directory

It’s More Fun in Multi-User Mode • Multi-user mode is reached after all the startup scripts run • The system is ready for more than one user to login at a time • Services (e. g. web, nfs daemon, telnet daemon, ftp daemon) are up and waiting to service requests

Jeopardy Time • Answer: The system won’t start. • Answer: The startup script method Linux uses. • Answer: It is the command used to properly shutdown the system.