Introduction to Unix Operating System

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Agenda An Overview of the UNIX Unix Installation

Pre Install Post Install

Startup & Shutdown Shell & Unix Command File System Account Management Network File System (NFS) Install Additional Software

Package Management Install Form Source Code

Process & Job control

An Overview of the Unix OS

At first, unix was designed to let a number of programmeraccess the same time and share its resource. The importantfeatures that make unix favorite are:

Multitasking Multiuser Portability Unix Tools Unix Communication Library of application software

Application Program

Kernel

Unix Structure

Hardware

Information before install

Size of Memory and Hard Disk Bandwidth and Memory of Video Card Mouse type Host Name Network information such as IP address,

Gateway,Network Address,DNS Server Time Zone Root Password

Choose Installation Class

Core system support Contains the minimum software required to boot and run Solaris.

but not include the OpenWindows software. End-user system support Contains the core system support software plus end user software,

which include OpenWindows and the Common Desktop Environment software.

Developer system support Contains the end-user software plus libraries, include files, man

pages, and programming tools for developing software. Entire distribution. Contains the entire Solaris 8 release. Entire distribution plus OEM system support Contains the entire Solaris 8 release software plus extended hardware support.

Partition Your HDD

Easy for manage All the space on the

disk is available for anyone to use

Allow finer control over such task as a backup

If one file system corrupted the others remain intact

Allow you control amount of storage for allocate type of use

Single VS Mulitple

Partition Scheme

Root (/) swap /usr /var /home

Post Install

Setup Network Connection Install Additional Software Configure others service such as

Printer ,NFS,WWW etc

Network Configuration

Display and configure the network interface using the “ifconfig” command

Ensure that the DNS is configured in file /etc/resolv.conf

Ensure that the routing table is set by command “netstat –r”

Ensure that the gateway is set in file /etc/defaultrouter

Start up

Before the UNIX operating system can perform correctly, there are a number of steps that must be followed

The failure of any one of these can mean that the system will not start.

It is important for the Systems Administrator to be aware of what happens during system startup so that any problems that occur can be remedied.

Booting - consists of the following steps

ROM PhaseBoot Program PhaseKernel initialization Phase Init Phase

Boot ROM Phase

After turn on power to the system, the ROM will display system identification and run self-test diagnostics to verify system hardware

Then the ROM will loads primary boot program called bootstrap program that store in bootblock of a boot device

Boot Program Phase

The boot strap program find and execute the secondary boot program from the file system and load it into memory

After the secondary boot program is loaded, it will load the kernel

Kernel initialization Phase

The kernel initializes itself (Create process control and other data structures)

Load device driver modules Mounts the necessary file system Create the process 0 (swapper) Then, bring the system to “initdefault” state

specified in /etc/inittab

Swapper

The first task for the kernel is to start the swapper process.

The swapper process is the part of the kernel that schedules all other process.

The swapper has process ID of 0 It’s first job is to start up the init process

Init Phase

The kernel start /sbin/init process, which starts other process by reading the /etc/inittab file

The /sbin/init process start the run control scripts

Run Control Script

Each init state has a corresponding series of run control scripts

The init process executes the /sbin/rc<n> script which execute a series of other scripts located in /etc/rc<n>.d directory

All run control scripts are also located in the /etc/init.d directory. These file are linked to run control scripts in /etc/rc<n>.d directory

Run LevelRun level Description

0 Halt the machine

1Single user mode. All file systems mounted, only small set of kernel processes running. only root can login.

2 multi-user mode , without remote file sharing

3multi-user mode with remote file sharing, processes, and daemons

4 undefine

5 used for to start X11 on boot

6 shutdown and reboot

s or S same as single-user mode

Shutdown

A UNIX machine should (almost) never be just turned off.

It is also important for the Systems Administrator to understand what the correct mechanism is to shut a UNIX machine down

There are a number of steps to carry out to ensure that the operating system and many of its support functions remain in a consistent state.

Commands to shut down /usr/sbin/shutdown /sbin/init /usr/sbin/halt /usr/sbin/reboot

Step before shutdown List of all logged-in user by “who” command.

You might sent broadcast message to let user know the system being shutdown

Flush file system buffer to physical disk by “sync” Use Shut Down command

Unix Shell

Unix is a layered operating system. The OS not allow applications accessing the hard

ware directly.

The shell acts as a command interpreter.

It takes each command and passes it to the operati

ng system kernel to be acted upon. And then displ

ays the results of this operation

Relationship for Kernel,Shell and Application

Features provided by the shell

The shell provides you with one or more of the following features.

TTypes of shellypes of shell

There are several different shells available for Unix. The most popular are described here.

• Bourne shell (sh)

• C shell (csh)

• Korn shell (ksh)

• Bourne Again Shell (bash)

Unix CommandUnix Command

A command is a program that tells the Unix system to d

o something.

Usually has the form: command [options] [arguments]

Commands are case sensitive. command and Command

are not the same.

Options and syntax for a command are listed in the ma

n page

Navigation and Directory Control Commands

Command/Syntax What it will do

ls [options] [directory or file] list directory contents or file permissions

cd [directory] change directory

mkdir [options] directory make a directory

pwd print working (current) directory

rmdir [options] directory remove a directory

File Maintenance Commands

Command/Syntax What it will do

chgrp [options] group file change the group of the file

chmod [options] file change file or directory access permissions

cp [options] file1 file2 copy file1 into file2; file2 shouldn't already exist.

This command creates or overwrites file2.

mv [options] file1 file2 move file1 into file2

rm [options] file remove (delete) a file or directory

(-r recursively deletes the directory and its contents)

Miscellaneous commands

Command/Syntax What it will do

cat [options] file concatenate (list) a file

more (or less or pg) [options] file page through a text file

tail [options] file display the last few lines (or parts) of a file

head [-number] file display the first 10 (or number of) lines of a file

which command reports the path to the command or the shell alias in use

who or w report who is logged in and what processes are running

date [options] report the current date and time

grep [options] file search specify pattern in the file

tar [options] file or directory pack and zip file

Unix file type

Regular file. A common file which contains data in text or binary.

Directory file. A file that contains name of other files and point to information on these files.

Symbolic link. A type of file that point to another file.

Unix file type

Character devices file. A type of file use for certain type of devices(read-write data in one character).

Block devices file. A type of file use for certain type of devices(read-write data in block).

FIFO. A type of file that use for interprocess communication,some time call named pipe.

Socket. A type of file that use for network communication.

Regular FileA regular file simply holds data. Perhaps the most common file type found in the Solaris Operating Environment are regular files, which allow you to store many different kinds of data. Regular files can hold ASCII text, binary data, image data, databases, application-related data, and more.

Directory fileDirectories store information that associates file names with inode numbers. Unlike regular files that can hold many different kinds of data, directories can hold only one kind.

Symbolic linkA symbolic link is a file that points to another file. Like directories,symbolic links contain only one kind of data. A symbolic link contains the pathname of the file to which it points.

File type & symbol

Type Symbol

Regular file -

Directory d

Character device c

Block device b

Unix domain socket s

Name pipes p

link file l

File Access Permission

Symbol Permission Means

r Read Can open and read content of file

w WriteCan write to file(Modify content) or delete it

x ExecuteCan execute the file(if it program or shell script)

- Denied Cannot read, write or execute file

Type

d r w x r - x r - -

Owner Group Others

- r w x - - x r - xExample 1

Example 2

22 + 21 + 20

The following example shows the use of the ls –la command to display permission file

Permission and Owner Command

chmod [–R] permission filename

Changes access permission of a file.

chown [-R] username:groupname filename

Changes the ownership of a file.

chgrp [-R] groupid filename

Changes the group ownership of a file.

Account ManagementEvery user on a UNIX machine must have an account.

Components of a user account are:

login name (also called a username). password. The numeric user identifier or UID. The numeric group identifier or GID. home directory. login shell. startup files.

Add use from GUI tools

Configuration files related to user accounts

/etc/passwd the password file, holds most of an account characteristics including username, UID, GID,GCOS information, login shell, home directory

/etc/shadow the shadow password file, a more secure mechanism for holding the password

/etc/group the group file, holds characteristics about a system's groups including group name, GID and group members

Fields in /etc/passwd file

Each line in the /etc/passwd file contains several fields, separated by a colon ( : ) , and is formatted as follows:

username:password:uid:gid:comment:home-directory:loginshell

Fields in /etc/shadow file

Each line in the /etc/shadow file contains several fields, separated by a colon ( : ) , and is formatted as follows:

username:password:lastchange:min:max:warn:inactive:expire

Startup Files Once the home directory is created the startup files can be

copied in or created. Again you should remember that this will be done as the root user and so root will own the files. You must remember to change the ownership.

For exampleThe following is example set of commands that will perform these tasks. mkdir home_directory cp -pr /etc/skel/.* home_directory chown -R login_name home_directory chgrp -R group_name home_directory chmod -R 700 home_directory

The NFS Distributed File SystemThe NFS environment contains the following components: NFS server – A system that contains the file resources to be shared with other

systems on the network. NFS client – A system that mounts the file resources shared over the network a

nd presents the file resources as if they were local.

Configuring the NFS File Server

To set up an NFS server, complete the following steps:

1. Edit the /etc/dfs/dfstab file and add those file resources to be automatically shared whenever the system enters run level 3.

For example: # share -F nfs /usr/share/man

2. Start the NFS server daemons by invoking the following: # /etc/init.d/nfs.server startThis shares the contents of the /etc/dfs/dfstab file.

The NFS Client Setup

1. Use the /usr/sbin/dfshares command to display a server’s available resources.

# dfshares host1

2. Use the /usr/sbin/mount command to access the remote file resource.

# mount host1:/usr/share/man /usr/share/man

3. To unmount the remote file resources from the client by using the /usr/sbin/umount command.

# umount /usr/share/man

Install Software Using Package Management

pkginfo command to display information about the software packages that have been installed

pkgadd command uncompresses and copies files from the installation media to the local system’s disk.

pkgrm command deletes all files associated with that package unless those files are also shared with other packages.

Install Software From Source Code

Tool & Utility for Compile Source codeCompiler & Library (GNUgcc & libgcc)Make (GNUmake)Autoconfigure (GNUautoconfigure)Compress/Uncompress (gzip/gunzip/tar)

Apache Web Server Install

Overview for install apache

$ ./configure --prefix=PREFIX

$ make

$ make install

NOTE: PREFIX by default use

"/usr/local/apache"

Configuration File

Finally you can customize your Apache HTTP server by editing the configuration files

$ vi PREFIX/conf/httpd.conf

$ vi PREFIX/conf/access.conf

$ vi PREFIX/conf/srm.conf

And Statrt web server by

$PREFIX/bin/apachectl start

Most Important Configure

ServerName avalon.bu.ac.th ServerAdmin root@avalon.bu.ac.th DocumentRoot "/usr/local/apache/htdocs"

*Note ServerRoot and DocumentRoot is difference meaning

A Unix process is an instance of an executing program It has a separate existence from all the other processes on the system we say that each process has its own address space

A unique number known as its process-id or pid

The pid of its parent process is the process which started it, usually a shell

Process & Job control

Process state Processes also have state

One a single-CPU machine, only one process is running

Most processes are sleeping, waiting for input or output to finish

There are a few other odd states: swapped, zombie, or stopped.

Job control The mechanism that shuffle processes from

foreground, background and stopped is known as job control

Job control requires three condition for support

A shell that support job control. The terminal driver in the kernel must support job

control Support for certain job-control signals must be

provided.

Foreground and Background Tasks

Unix allows running processes to be

disconnected from their terminals

Unix has the concept of foreground processes

which are attached to a user's terminal

background processes, which have no terminal

to read from

Job control & process management command

ps - report process status kill - terminate or signal processes

Control process execution jobs - report job status bg - bring job to background process fg - bring job to foreground process stop - stop the job

Signals

Signals are a technique used to notify a process that

some condition has occurred.

Ordinary users can only send signals to their

own processes.

The command to send signal to process is “kill”. example: $ kill -signal processid

Here are some examples:

$ sleep 100 # Wait for 100 seconds, then go back to shell ctrl-C # Kill sleep process $ sleep 100 & # Wait for 100 seconds in the background $ jobs # Show list of jobs [1] + Running sleep 100 & $ kill SIGSTOP %1 # Stop sleep process (job number 1) $ jobs [1] + Stopped (SIGSTOP) sleep 100 & $ bg %1 # Put sleep in background $ fg %1 # Bring sleep in foreground, reattached # to the terminal