Week 1: IT System Components Operating Systems File Systems Processes and Job Control Devices and...

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Week 1: IT System Components

Operating Systems

File Systems

Processes and Job Control

Devices and Controllers

ReadingsBurgess, Chapter 2Mikalsen, Chapter 1


2

Operating Systems

• Software which shares and controls hardware resources of a computer

• Shields user from low-level details• Provides simple access to frequently needed facilities

– Technical layer (kernel & drivers)– File I/O– User Interface


4

Operating Systems

OS Users Tasks CPUsMS/PC DOS S S 1Windows 3X S NonPre-M 1

Mac System7 S NonPre-M 1Windows 9X S M- 1AmigaDOS S M- 1

MTS M M 1Unix-like M M n

VMS M M 1NT/2000/XP S/M M n

Unix-Like OS Manufacturer TypeBSD Univ.California Berkeley BSD

SunOS (Solaris 1) Sun Microsystems BSD/Sys5Solaris (2) Sun Microsystems Sys5/BSD

Ultrix DEC/Compaq BSDOSF1/Digital Unix DEC/Compaq BSD/Sys5

HPUX Hewlett-Packard Sys5AIX IBM Sys5/BSDIRIX Silicon Graphics Sys5

GNU/Linux GPL Free Software Posix (SysV/BSD)Unixware Novell Sys5


5

Operating Systems

• Multi-programming (Processes/Threads) allows logical concurrency: multi-user and EventDriven systems, which yields Client/Server architecture!

• User Interfaces– Shell, CLI, GUI

• Logfiles, Audit trails, Policies: accounting, security, reliability, performance

• Supervisor, Superuser, root user


6

Comparing UNIX & Windows

• Compare Shell Commands– See Table 2.1 in Burgess (Pg22)

• Compare Directory/File structure– See Table 2.2 in Burgess (Pg23)

• Compare Software concepts– See Table 2.3 in Burgess (Pg24)


7

UNIX-like OS

chmod

chown

chgrp

emacs

kill

ifconfig

lpq

lpr

mkfs/newfs

mount

netstat

nslookup

ps

route

setenv

su

tar

traceroute

Windows

CACLS

CACLS

No direct equivalent

Wordpad or emacs (in GNU tools)

kill (in resource kit)

ipconfig

lpq

lpr

format & label

net use

netstat

nslookup

pstat (in resource kit)

route

set

su (in resource kit)

tar (in Cygwin tools)

tracert

Table 2.1

Comparison of UNIX and Windows Shell commands

Burgess Pg 22



8

UNIX-like OS

/usr

/bin or /usr/bin

/dev

/etc

/etc/fstab

/etc/group

/etc/passwd

/etc/resolv.conf

/tmp

/var/spool

Windows

%SystemRoot% usually points to C:\WINNT

%SystemRoot%\System32

%SystemRoot%\System32\Drivers

%SystemRoot%\System32\Config

No equivalent

%SystemRoot%\System32\Config\SAM* (binary)

%SystemRoot%\%\System32\Config\SAM* (binary)

%SystemRoot%\System32\DNS\*

C:\Temp

%SystemRoot%\System32\Spool

Table 2.2: Comparison of Unix and Windows directories and files, Burgess Pg 23



9

Unix-like OS

Standard libraries

Unix libraries

Symbolic/hard Links

Processes

Threads

Long filenames

Mount disk on directory

endl is LF

UID (User ID)

groups

ACLS (non standard)

Permission bits

Shared libraries

Environment variables

Daemons/services/init

Windows

WIN32 API

Posix compatibility library

Hard links (short cuts)

Processes

Threads

Long filenames on NTFS

Mount drive A: B: etc

endl is CR LF

SID (Subject ID)

groups

ACLs

(Only in ACLs or with Cygwin)

DLL's

Environment variables

Service control manager

Table 2.3 Comparison of UNIX and Windows software Concepts (Pg 24)



10

Unix-like OS

DNS/DHCP/bootp (free)

X windows

Various window managers

System Admin GUI (non-standard)

cfengine

Any client-server model

rsh

Free Software

Perl

Scripts

Shells

Primitive security

Dot files for configuration

Pipes with comm1 I comm2 Configuration by text/ascii files

Windows

DNS/DHCP (NT server)

X windows

Windows GUI

System Adrnin GUI (Standard)

cfengine as of 1.5.0

Central server model

limited implementation in server

Some free software

Perl + WIN32 module

Scripts

DOS Command window

Primitive security

System registry

Combinations comm1 l comm2

Config by binary database

Table 2.3 Comparison of UNIX and Windows software Concepts (Pg 24)



11

File Systems

Most OS’s now have hierarchical file systems (Directories and Links)

• Unix File Hierarchy• File Names• File structure related to function• Link files• File Access Control

– Owner, Group, Other method (permission list)– ACL method – user1 rwx, user2 rwx,…


12

File Permission Checking

• User OPEN(“filename”,mode) system callmode = Create, Read, Write, Append, etc..

• System searches directory: locates “filename”

• Compares users name (UID) of program with Owner of file. If not same, repeat for Group (GID). Else use Other.

• Compares “mode” with files permBits: Error if “mode” exceeds files allowed permissions.eg. When mode=Read and permBits=rwx,-,- (700) and UID not = Owner


13

Access Control List checking

• Instead of permBits, directory entries for files have ACLs• ACLs are of the form:

User1:permBits,User2:permBits,… (with wildcards!)

• ACLs may be inherited from parent directory• Checking involves a search of the file’s ACL to match the

name of the user/group running the program, with the user/group in the ACL

• If matched, the permission settings from the list are applied


14

Network File Systems

For sharing file systems between hosts. Methods include:

• Drive redirection– NET USE in DOS/Windows– MAP in Novell

• Directory redirection– mount in UNIX

• Share & Subscribe, Export & Mount

• Configured mount or automount• Distributed Directory systems


15

Network File Systems

• Windows– LAN Manager, Workgroups (SMB)

• Unix NFS (originally by SUN)• DFS (part of OSI DCE)• Common Internet File System (CIFS) “samba”

• Andrew File System• Netware NDS by Novell• Windows Advanced File System


Multiprogramming…


17

Processes

• Each process is a collection of resources:Instance of a running program in RAM, current directory, open files

with current position, user and group ID, space and time limits, etc…

• Processes are “time-sliced” by OS scheduler– Various policies and queues of waiting processes

• A process may also contain concurrent paths of execution called Threads

• To see process hierarchyUnix: ps – ef or topsWindows: taskmanager


18

Processes

• Unix Process Hierarchy– New processes are replicas of existing ones

– Parent process may wait for child processes to exit before proceeding (Synchronous model)

– When “parent” does not wait, “child” is said to be “running in the background”

– Processes may send termination status message to parent process


19

Processes

Windows/NT Process model– Very similar to the Novell NLM model

– Background processes are detached from foreground session

– Background jobs continue after logout

– Any console user may shutdown

– Shutdown terminates all processes

– Easier to manage concurrent functions as threads within an existing program (not different objects)


20

Process Environment

• Chains of processes share environment• Environment may be implied or explicit• Environment Variables are text strings• Variables usually set by user or script• Environment is inherited by new processes.

This is how command parameters are passed from parent to child. But changes made in local environment are not returned back to parent process environment.


21

Things of Special interest to SysAdmins

• Logs and Audit Trails– A detailed list of actions recorded by OS

– File system Logs used to reinstate data

– Usage Logs used for billing

– Auditing used for security> Trace source of activity> Provide non-repudiation


22


• Privileged Accounts– A user with power to configure/maintain

> root, Administrator, SysOp, etc..– Can access or do anything !!– Is actually very dangerous– Should not be used as everyday login. . . .

use only when required– Trusted host concept in TCP/IP can now be easily circumvented

because everyone has superuser access on their own PC !!


23


• Knowing how to care for your hardware– Read the instructions!– Understand interfaces & connectors– Know capabilities and limitations of devices

> Speeds> Capacities> Compatibilities

– Know how to handle components> Avoid damage due to Static Discharge> Packaging and transport> Assembly


24


• Types of disk drives– ATA - IDE

– SCSI

– Serial ATA

• Types of Memory devices– Fast Page, EDO, SDRAM, ECC, etc…

• BIOS and NVRAM settings


25


• Easy Systems Integration– System built from identical parts

– Applies to hardware and software


IT System Components

(end)

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Week 1: IT System Components Operating Systems File Systems Processes and Job Control Devices and...

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