1. Operating System Basics
What does an Operating System do?
- A way to execute programs
(user/computer interface)
- Allocates resources to programs
efficiently and fairly
- Manages resources
- memory, cpu, devices, file system
- Schedules jobs
- Provides security and protection
from others

2. Operating System Basics
Nutt: “... only the most skilled and
experienced programmers are allowed
to design and modify a computer's
operating system.”
Process – a program in execution
- has an address space
- process table, parent-child relationship
The Shell

3. Operating System Overview
Thread – a unit of work. Multithreading
allows a process to be divided into a
number of threads so multiple things
can be done concurrently.
Deadlocks -
Memory Management – memories not
big enough -> virtual memory
I/O – Programmed, Intr driven, DMA
Files, Security and more...

4. File management OS responsible for managing data on
disks (programs, and data).
Filesystems – a general way to store
files
File descriptors – a structure with info
about open files
File types – several types of files
Big advancement: ZFS

5. Unix 1970 – Bell Labs version 7 – 1978 – ancestor to most
modern UNIX systems
BSD, SYSV, Linux, (Open)Solaris
UNIX kernel – core of OS
system calls – user hooks into kernel
library calls – user land routines
- eventually end up doing system calls

6. Unix Daemons – processes running (in the
background) usually to perform some
service.
Example daemons – httpd, smtpd, sshd
cron – clock daemon (start jobs at a
time given in crontab)
File permissions
- ls, chmod
- rwx, user, group, other

7. Unix development environment
Editors – vi, emacs
make
compilers – cc, gcc
debuggers – dbx, gdb
IDE – sunstudio, eclipse
Trace system calls: truss, strace
Powerful tracing: Dtrace
Homework: run 'truss ls'

8. Booting a Unix System Boot block boot loader (grub) start kernel
start init (usually pid 1)
start start-up scripts
- flavors: BSD, SYSV, Solaris SMF
- usually start services the system
provides (many daemons)

9. Start up systems BSD rc scripts - shell scripts ran during boot
- check filesystems and mount
- start services and other things
- many things in a few scripts
SYSV init.d scripts
- Have run levels (S, 0, 1, 2, 3..)
- Scripts run when entering a run level
- Have one script for each service

10. Solaris SMF Service Management Facility Introduced in Solaris 10
A big improvement over the past
Services are defined
commands: svcs, svcadm, svccfg
Knows dependencies
has milestones
Will restart a daemon that dies
XML files and scripts