linux module 1

8/7/2019 Linux Module 1

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LinuxLinuxFundamental AdministrationFundamental Administration

in a Linux environmentin a Linux environment

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Module 1Module 1Role of a sys adminRole of a sys admin

System DocumentationSystem DocumentationHelpHelp

File system layoutFile system layout4/6/20114/6/2011


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File SystemFile System

DirectorysDirectorys Locations for files andLocations for files anddirectories.directories.

SubdirectorysSubdirectorys-- A directory that isA directory that isbelow a directory.below a directory.

DocumentsDocuments ASCII, ASCII,

ApplicationsApplications databases, worddatabases, wordprocessors, spreadsheetsprocessors, spreadsheets

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File System: UnixFile System: Unix

Unix File Str ct re

bin sbin lib

bin sbin etc

local

sr dev etc

ser ser2 ser3

home lib var boot bin

floppy cdrom

mnt sbin root proc

Root (/)

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Filesystem Hie y St ndardFilesystem Hierarchy Standard

1993 Linux community formed a1993 Linux community formed aproject too standardize theproject too standardize thefilesystem layout for all generalfilesystem layout for all general

purpose Linux distributionspurpose Linux distributions Known as the Linux FilesystemKnown as the Linux Filesystem

Standard but later renamed to theStandard but later renamed to the

Filesystem Hierarchy StandardFilesystem Hierarchy Standard FHS defines two categories of dataFHS defines two categories of data

use: Data Sharing and Datause: Data Sharing and DataModificationModification

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Data SharingData Sharing

ShareableShareable -- Can be used by multiple hostCan be used by multiple hostsystems on a network. These files containsystems on a network. These files containgeneralgeneral--purpose information such as userpurpose information such as user

datafiles, executables and commondatafiles, executables and commonconfiguration filesconfiguration files

NonNon--shareableshareable -- Data is not shareableData is not shareablewhen it is linked to a specific host. For, awhen it is linked to a specific host. For, aunique configuration file such as theunique configuration file such as thepasswd file and system logspasswd file and system logs

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DataModi icationDataModi ication

VariableVariable -- Data is considered variableData is considered variablewhen it changes by natural andwhen it changes by natural and

frequentfrequentprocesses(/var/log/messages)processes(/var/log/messages)

StaticStatic -- This data is left alone for theThis data is left alone for themost part remaining the same frommost part remaining the same from

day to day or even year to year.day to day or even year to year.

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FHS Data Ty esFHS Data Ty es

Sharable Non-SharableStatic /usr

/usr/local

/etc

/bootVariable /var/mail

/home/var/log/proc

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The root FilesystemThe root Filesystem

Must contain utilities and filesMust contain utilities and filessufficient to boot the operatingsufficient to boot the operatingsystemsystem

Should contain utilities needed byShould contain utilities needed bythe system administrator to repair orthe system administrator to repair orrestore a damaged systemrestore a damaged system

Should be relatively smallShould be relatively small Software should not create files orSoftware should not create files or

directories in the root filesystemdirectories in the root filesystem

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The usrFilesystemThe usrFilesystem

Contain system utilities andContain system utilities andprograms that do not appear in theprograms that do not appear in the

root partitionroot partition User programs will often appear inUser programs will often appear in

/usr/bin/usr/bin

Some system administrationSome system administrationprograms may appear in /usrprograms may appear in /usrfilesystem as wellfilesystem as well

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The arFilesystemThe arFilesystem

Contains data such as printer spoolsContains data such as printer spoolsand log files that vary over timeand log files that vary over time

Is always changing and growing andIs always changing and growing andoften has its own partitionoften has its own partition

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root Filesystem O erviewroot Filesystem Overview

File file system available upon booting isFile file system available upon booting isthe root filesystem (/)the root filesystem (/)

In some cases, the root filesystemIn some cases, the root filesystem

contains everything on the systemcontains everything on the system

Best practice is to define multipleBest practice is to define multiplepartitions containing one or more of thepartitions containing one or more of the

directories found below root (/)directories found below root (/) When Linux boots, the partitions are mountedWhen Linux boots, the partitions are mountedand together create a single filesystemand together create a single filesystem

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//

Top of the filesystem hierarchyTop of the filesystem hierarchy

Some directories must always be aSome directories must always be a

part of the root filesystem to allowpart of the root filesystem to allowLinux to bootLinux to boot

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/bin and/sbin/bin and/sbin

Contains required system binaryContains required system binaryprogramsprograms

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/dev/dev

Contains device filesContains device files

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/etc/etc

Contains boot configurationContains boot configurationinformationinformation

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/lib/lib

Contains program librariesContains program libraries

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/boot/boot

Holds static files used by the bootHolds static files used by the bootloaderloader

Can be placed on a separate partitionCan be placed on a separate partition For use with older versions of lilo,For use with older versions of lilo,

usually on a partition below theusually on a partition below the10241024thth cylinder of a hard drive.cylinder of a hard drive.

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/home/home

Holds user filesHolds user files

Often placed on a separate partitionOften placed on a separate partition

Normally becomes the largestNormally becomes the largestpartition on the system and can evenpartition on the system and can evenbe placed on a separate physical diskbe placed on a separate physical disk

Can be shared over the network toCan be shared over the network tocentralize users files.centralize users files.

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/tm/tm

Programs use this for temporary filesPrograms use this for temporary files

Best practice to place it on aBest practice to place it on a

separate partition to preventseparate partition to preventtemporary files from filling uptemporary files from filling upvaluable disk space on the rootvaluable disk space on the rootpartitionpartition

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/var/var

Log files are stored hereLog files are stored here

Email is stored hereEmail is stored here

Print queues are stored herePrint queues are stored here RedHat stores the Apache web docsRedHat stores the Apache web docs

herehere

NIS files stored hereNIS files stored here

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/usr/usr

Holds a hierarchy of directoriesHolds a hierarchy of directoriescontaining user commands, sourcecontaining user commands, sourcecode, and documentationcode, and documentation

Often quite large in sizeOften quite large in size

Should have its own partitionShould have its own partition

/usr/sbin holds sys admin/usr/sbin holds sys adminexecutablesexecutables

/usr/bin holds user executables/usr/bin holds user executables

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Binary File LocationsBinary File Locations

User Commands System AdministrationCommands

Vendor-supplied , essential /bin /sbinVendor-suppliednonessential

/usr/bin /usr/sbin

Locally supplied,nonessential

/usr/local/bin /usr/local/sbin

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File Location CommandsFile Location Commands

whichwhich

findfind

locatelocate updatedbupdatedb

whatiswhatis

aproposapropos

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which Overviewwhich Overview

Shows the location of a commandShows the location of a commandand displays the full pathname. Usesand displays the full pathname. Usesthe PATH variable to search for thethe PATH variable to search for thecommand.command.

Command Format: whichCommand Format: which commandcommand

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find Overviewfind Overview

Locates files that match anLocates files that match anexpressionexpression

Works recursivelyWorks recursively

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find Syntax and O tionsfind Syntax and O tions

Syntax:Syntax:

find paths expressionfind paths expression

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locate Overviewlocate Overview

Locates files who names match oneLocates files who names match oneor more patternsor more patterns

Searches an index of files previouslySearches an index of files previouslycreatedcreated

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locate Syntax and O tionslocate Syntax and O tions

Syntax:Syntax:

locatelocate patternspatterns

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u datedb Overviewu datedb Overview

Refreshes or creates the slocateRefreshes or creates the slocatedatabase indatabase in/var/lib/slocate/slocate.db/var/lib/slocate/slocate.db

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u datedb Syntax and O tionsu datedb Syntax and O tions

Syntax:Syntax:

updatedb [options]updatedb [options]

Options:Options: --ee directoriesdirectories (exclude a comma(exclude a comma--

separated list of directories from theseparated list of directories from thedatabase)database)

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whatis Overviewwhatis Overview

Search the whatis database for exactSearch the whatis database for exactmatches to keywords and display thematches to keywords and display theresultsresults

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whatis Syntax and O tionswhatis Syntax and O tions

Syntax:Syntax:

whatiswhatis keywordskeywords

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apropos Overviewapropos Overview

Search the whatis database forSearch the whatis database forpartial word matches to keywordspartial word matches to keywordsand display the resultsand display the results

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Objective 1: Use andManageObjective 1: Use andManage

Local System DocumentationLocal System Documentation Text and PagingText and Paging

The man FacilityThe man Facility

Information in /usr/docInformation in /usr/doc Info PagesInfo Pages

OdditiesOddities

Using the locate CommandUsing the locate Command

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Documentation OverviewDocumentation Overview

System Administrators should beSystem Administrators should becomfortable with navigating throughcomfortable with navigating throughdocumentation in the event that hedocumentation in the event that heor she needs helpor she needs help

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Documentation ObjectivesDocumentation Objectives

Use and Manage Local SystemUse and Manage Local SystemDocumentationDocumentation

Find Linux Documentation on theFind Linux Documentation on theInternetInternet

Write System DocumentationWrite System Documentation

Provide User SupportProvide User Support

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Use andManage Local SystemUse andManage Local System

DocumentationDocumentation Text and PagingText and Paging


Information in /usr/docInformation in /usr/doc Info pagesInfo pages

OdditiesOddities


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Text and PagingText and Paging

Text and Paging OverviewText and Paging Overview

Paging ProgramsPaging Programs

lessless

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Text and Paging OverviewText and Paging Overview

Each Linux system is configured withEach Linux system is configured withextensive documentation from:extensive documentation from: ProgrammersProgrammers

AuthorsAuthors Other ContributorsOther Contributors

Some documentation is quite formal whileSome documentation is quite formal whileother documentation is fairly informalother documentation is fairly informal

Combined, this documentation offers aCombined, this documentation offers arobust body of information for users androbust body of information for users andsystem administratorssystem administrators

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Paging ProgramsPaging Programs

more was a popular paging program on Unixmore was a popular paging program on Unixsystemssystems

more would give users one more screen ofmore would give users one more screen ofinformationinformation

more is known to be limited in its capabilities somore is known to be limited in its capabilities sothe less command was developedthe less command was developed

less is similar to more but offers more capabilitiesless is similar to more but offers more capabilities

less does not read all of its input before starting,less does not read all of its input before starting,

which makes it faster for large inputwhich makes it faster for large input Can also use less commands to control theCan also use less commands to control the

behavior of lessbehavior of less

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less Commandsless Commands

Command DescriptionSpace Scroll forward one screenD Scroll forward one-half screen

Return Scroll forward one lineB Scroll backward one screenU Scroll backward one-half screenY Scroll backward one lineg Go tot he beginning of the text G Go to the end of the text /pattern Search forward for a pattern which can be a regular expression

?pattern Search backward for pattern which can be a regular expressionH Display a help screen:n Display next file from command line:p Display previous file from command line

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The man Facility OverviewThe man Facility Overview

man Commandman Command

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The man Facility OverviewThe man Facility Overview

The man facility was created to putThe man facility was created to putdocumentation books on the systemdocumentation books on the system

manpages are available for mostmanpages are available for mostcommands on the systemcommands on the system

manpages are also available formanpages are also available forimportant files, shells, devices andimportant files, shells, devices andother items on your Linux systemother items on your Linux system

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The man CommandThe man Command

Formats and displays man pages onFormats and displays man pages ona topic using a pagera topic using a pager

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man Syntax and Optionsman Syntax and Options

Syntax:Syntax:

man [options] [section] commandman [options] [section] command

Options:Options: --a Instructs man to display alla Instructs man to display all

manpages that match a name in amanpages that match a name in asequential fashionsequential fashion

--d Display debugging informationd Display debugging information --w Print the locations of manpagesw Print the locations of manpages

instead of displaying theminstead of displaying them

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Man SectionsMan Sections

Sect. Description

1 Executable programs or shell commands

8 System Administration commands

2 System calls

3 Library calls

4 Special files (usually found in /dev)

5 File formats and conventions

6 Games

7 Macro packages and conventions

9 Kernel routines

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Information in /usr/docInformation in /usr/doc

Some Linux users contribute theirSome Linux users contribute theirknowledge in the form of HOWTOknowledge in the form of HOWTOguides, FAQs, README files and evenguides, FAQs, README files and even

exhaustive manualsexhaustive manuals Most of this documentation ends up inMost of this documentation ends up in

/usr/doc/usr/doc

Most is ASCII and can be displayedMost is ASCII and can be displayed

using a pager programusing a pager program Contents of /usr/doc can be categorizedContents of /usr/doc can be categorized

as follows:as follows: Package RelatedPackage Related

FAQFAQ

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Package elatedPackage elated

usually useful bits of informationusually useful bits of informationincludes with the program sourceincludes with the program source

Contains documentation files that areContains documentation files that areoften specific to a version of aoften specific to a version of apackagepackage

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FAQFAQ

Contains detailed information in aContains detailed information in aQ&A formatQ&A format

Man important FAQs resides inMan important FAQs resides in

usr/doc/FAQusr/doc/FAQ FAQs are often formatted in:FAQs are often formatted in:

HTML (web browser friendly)HTML (web browser friendly)

ps (printer friendly)ps (printer friendly) txt (plain text)txt (plain text)

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HOWTO documentsHOWTO documents

Details information on how toDetails information on how toperform a certain taskperform a certain task

Often serve as reference material forOften serve as reference material fornew administratorsnew administrators

Often stored in /usr/doc/HOWTOOften stored in /usr/doc/HOWTO

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InfopagesInfopages

Are part of a system called textinfoAre part of a system called textinfowhich uses a single source file towhich uses a single source file todisplay information on screen and ondisplay information on screen and onpaperpaper

Is hypertext and creates a browserIs hypertext and creates a browserlike interface on a terminal orlike interface on a terminal or

terminal windowterminal window

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info Commandsinfo Commands

Command DescriptionTab Mov among y rt xt links

Ent r ollow y rt xt linkst rn to t topof t menu? List all info commandsP andn Move toprevious andnextpages respectivelyu Moveupone level in t eTextinfo ierarc yq Terminate t e systemh Showaprimer for first timeusers

/string Enter a string/patter Search forward for pattern,which canbea regular expression

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5555


The locate command is handy as itThe locate command is handy as itcan return all instances of thecan return all instances of thecommand or command fragment youcommand or command fragment youenterenter

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5656

Documentation on the netDocumentation on the net

The Linux Documentation ProjectThe Linux Documentation Project

Usenet NewsgroupsUsenet Newsgroups

Mailing ListsMailing Lists Vendor Web Sites and OtherVendor Web Sites and Other

ResourcesResources

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5757

The Linux DocumentationThe Linux Documentation

ProjectProject Most documentation, includingMost documentation, including

HOWTOs, is part of an organizedHOWTOs, is part of an organizedapproach to system documentationapproach to system documentation

Linux Documentation Project (LDP) isLinux Documentation Project (LDP) isa group of writers, proofreaders anda group of writers, proofreaders andeditors to create systemeditors to create systemdocumentation for Linuxdocumentation for Linux

The url is http://www.linux.orgThe url is http://www.linux.org

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The Linux DocumentationThe Linux Documentation

ProjectProject Documentation handled by LDP includesDocumentation handled by LDP includes

online documents, manpages, HOWTOsonline documents, manpages, HOWTOsand a complete set of reference guidesand a complete set of reference guidesincluding:including: Installation and Getting Started GuideInstallation and Getting Started Guide

The Linux Users GuideThe Linux Users Guide

The Linux System Administrators GuideThe Linux System Administrators Guide

The Linux Programmers GuideThe Linux Programmers Guide

The Linux KernelThe Linux Kernel

The Linux Kernel Hackers GuideThe Linux Kernel Hackers Guide

The Linux Kernel Module Programming GuideThe Linux Kernel Module Programming Guide

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Usenet NewsgroupsUsenet Newsgroups

Worldwide bulletin board serviceWorldwide bulletin board service

Messages are posted to a users localMessages are posted to a users localnews server in a newsgroupnews server in a newsgroup

Can usually access Usenet contentCan usually access Usenet contentthrough your ISPthrough your ISP

Can read messages with a newsCan read messages with a newsreader applicationreader application

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Important Usenet NewsgroupsImportant Usenet Newsgroups

comp.os.linuxcomp.os.linux

comp.os.linux.advocacycomp.os.linux.advocacy

comp.os.linux.developmentcomp.os.linux.development

comp.os.linux.announcecomp.os.linux.announce

comp.os.linux.hardwarecomp.os.linux.hardware

comp.os.linux.answerscomp.os.linux.answers

comp.os.linux.networkingcomp.os.linux.networking comp.os.linux.xcomp.os.linux.x

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Mailing ListsMailing Lists

Mailing list is an email autoresponderMailing list is an email autoresponderwith a known list of mail recipientswith a known list of mail recipients

Inbound mail to the list server will beInbound mail to the list server will bemirrored to each of the othermirrored to each of the otherrecipients on the listrecipients on the list

Mailing list mail is more likely to beMailing list mail is more likely to be

read by subscribers than usenetread by subscribers than usenetinformationinformation

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6262

CertificationCertification

http://www.brainbench.comhttp://www.brainbench.com

http://www.linuxcertification.comhttp://www.linuxcertification.com

http://www.lpi.orghttp://www.lpi.org http://www.redhat.com/rhcehttp://www.redhat.com/rhce

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6363

CommerceCommerce

http://www.elinux.comhttp://www.elinux.com

http://www.linuxcentral.comhttp://www.linuxcentral.com

http://www.linuxmall.comhttp://www.linuxmall.com

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6464

DistributionsDistributions

http://www.calderasystems.comhttp://www.calderasystems.com

http://www.debian.orghttp://www.debian.org

http://www.linuxhttp://www.linux--mandrake.commandrake.com http://www.redhat.comhttp://www.redhat.com

http://www.slackware.comhttp://www.slackware.com

http://www.suse.comhttp://www.suse.com http://www.turbolinux.comhttp://www.turbolinux.com

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6666

GeneralGeneral

http://www.linux.comhttp://www.linux.com

http://www.linux.orghttp://www.linux.org

http://www.linuxberg.comhttp://www.linuxberg.com

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6767

GUIsGUIs

http://www.afterstep.orghttp://www.afterstep.org

http://www.eazel.comhttp://www.eazel.com

http://www.gnome.orghttp://www.gnome.org http://www.kde.orghttp://www.kde.org

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6868

NewsNews

http://slashdot.orghttp://slashdot.org

http://www.linuxplanet.comhttp://www.linuxplanet.com

http://www.lwn.comhttp://www.lwn.com http://www.linuxjournal.comhttp://www.linuxjournal.com

http://www.linuxtoday.comhttp://www.linuxtoday.com

http://www.linuxpr.comhttp://www.linuxpr.com http://www.oreillynet.comhttp://www.oreillynet.com

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6969

Open SourceOpen Source

http://www.fsf.orghttp://www.fsf.org

http://www.gnu.orghttp://www.gnu.org

http://www.kernelnotes.orghttp://www.kernelnotes.org http://freshmeat.orghttp://freshmeat.org

http://www.sourceforge.nethttp://www.sourceforge.net

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7070

ProjectsProjects

http://www.apache.orghttp://www.apache.org

http://www.squidcache.orghttp://www.squidcache.org

http://www.linuxrouter.orghttp://www.linuxrouter.org http://www.linuxppc.orghttp://www.linuxppc.org

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7171

Search EnginesSearch Engines

http://www.google.comhttp://www.google.com

http://www.altavista.comhttp://www.altavista.com

http://www.northernlight.comhttp://www.northernlight.com http://www.yahoo.comhttp://www.yahoo.com

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7272

SupportSupport

http://www.linuxcare.orghttp://www.linuxcare.org

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7474

X Window SystemX Window System

http://www.x.orghttp://www.x.org

http://www.sgree86.comhttp://www.sgree86.com

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Role ofa SystemRole ofa SystemAdministratorAdministrator

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SuperuserSuperuser

Known as the root userKnown as the root user

Has a uid of 0Has a uid of 0

Most powerful account on the systemMost powerful account on the system By default cannot remotely login asBy default cannot remotely login as

rootroot

By default cannot use root as an ftpBy default cannot use root as an ftpuseruser

Home directory of /rootHome directory of /root4/6/20114/6/2011


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SuperuserSuperuser

Should not use superuser forShould not use superuser foreveryday use because:everyday use because:

Normally do not need rootNormally do not need root--level accesslevel access

If a mistake is made when logged on asIf a mistake is made when logged on asroot, it can have systemroot, it can have system--widewideimplicationsimplications

Can read other users email and filesCan read other users email and fileswhich can cause ethical issueswhich can cause ethical issues

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Process UsersProcess Users

Restricted access to processRestricted access to process--requiredrequiredresourcesresources

Found on all UNIX and Linux systemsFound on all UNIX and Linux systems

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Unprivileged UsersUnprivileged Users

Regular users that have restricted toRegular users that have restricted toareas/activities for which they have beenareas/activities for which they have beengiven permissionsgiven permissions

Typically need only run programs andTypically need only run programs andsave documents and datasave documents and data

Created as necessary by a systemCreated as necessary by a systemadministrator using the useradd commandadministrator using the useradd command

or the LinuxConf graphical utilityor the LinuxConf graphical utility

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8080

Module : UserModule : User

ManagementManagement/etc/passwd, /etc/shadow,/etc/passwd, /etc/shadow,/etc/group, /etc/gshadow/etc/group, /etc/gshadow

Useradd, usermod, userdelUseradd, usermod, userdelGroupadd, groupmod,Groupadd, groupmod,

groupdelgroupdel

Chage, passwdChage, passwd

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8181

/etc/passwdfile/etc/passwdfile

steve:x:500:100:steve gamblin:/home/steve:/bin/bash

This is the file that contains account information ofusers in a Linux system. It can be read by everyone

who is logged into the server. Only the root account haswrite privileges.

Username:password:uid:gid:comment:home:shell

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/etc/passwd: username/etc/passwd: username

Most unixes up to 8 charactersMost unixes up to 8 characters

Has to start with a letterHas to start with a letter

May have numbersMay have numbers Should be lowercaseShould be lowercase

Must be uniqueMust be unique

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8383

/etc/passwd: password/etc/passwd: password

If it contains an "x" then theIf it contains an "x" then thepassword is in a special file calledpassword is in a special file called/etc/shadow/etc/shadow

Most unixes min 6 charactersMost unixes min 6 characters

Most unixes up to 8 charactersMost unixes up to 8 characters

May contain spacesMay contain spaces

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8484

/etc/passwd: uid/etc/passwd: uid

Uid is the unique numerical id number forUid is the unique numerical id number forthe user.the user.

Technically should be unique, but accountsTechnically should be unique, but accounts

can be setup to have the same uidcan be setup to have the same uid Odd things can happen with same uidsOdd things can happen with same uids

Generally uid from 0 to 99 reserved forGenerally uid from 0 to 99 reserved forsystem accountssystem accounts

100 to 60000 for normal users100 to 60000 for normal users

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/etc/passwd: gid/etc/passwd: gid

Number of the primary group thatNumber of the primary group thatthe user belongs to.the user belongs to.

The users secondary groupThe users secondary group

memberships defined in thememberships defined in the/etc/group file/etc/group file

Gids from 0 to 99 reserved forGids from 0 to 99 reserved forsystem groups.system groups.

100 to 60000 for general use.100 to 60000 for general use.

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/etc/passwd: Comment/etc/passwd: Comment

This may or may not containThis may or may not containinformation.information.

Should be kept to a minimumShould be kept to a minimum

Usually contains users real nameUsually contains users real name

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/etc/passwd: home/etc/passwd: home

Contains the location of the homeContains the location of the homedirectorydirectory

Most system accounts do not have aMost system accounts do not have ahome directoryhome directory

The root accounts home directory isThe root accounts home directory isusually /rootusually /root

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/etc/passwd: Default Shell/etc/passwd: Default Shell

This contains the default shell thatThis contains the default shell thatthe Sys Admin has assigned to thethe Sys Admin has assigned to theuser.user.

In Linux most common shell is bashIn Linux most common shell is bash

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/etc/shadow/etc/shadow

steve:$1$wW4mgdYE$yQ2eQrU:11768:0:99999:7:::

This file contains the password for the user. It is onlyreadable by the root user.

Username:password:Days since Jan 11970 that password has been changed:Days before password can be changed:

Days after which password must be changed:Days before password is to expire that user is warned:Days after password expires that account is disabled:Days since Jan 1,1970 that account is disabled:A reserved field:4/6/20114/6/2011


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UserManagement: useraddUserManagement: useradd

To add user accounts by commandline you use theuseradd command.Command Format: useradd [options] username

Options-c "comment" Comment field-d /home/user home directory-u uid specify uid-g group specify primary gid-G group1, secondary groups-m create home directory-s /bin/shell specify default shell-k /etc/skel specify default profiles-n turns off group same as user creation

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Useradd ExampleUseradd Example

Example:To create a user called bob.

useradd bob

To create a user called billy, but you want to turn offthe group creation and to have billy assigned to theusers group. and you want to add in Billy's name in the

comment field

useradd n c "Billy Smith" billy

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UseradddefaultsUseradddefaults

You can define preset options, so that you don't have tospecify them when you use the useradd command.

useradd D will list all of the defaults defined.

Command Format: useradd D [options]

Options-b home dir sets default home directory-e default expiry date sets default expiry date-g group sets default group *-s shell sets default shell4/6/20114/6/2011


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UseraddUseradd D ExampleD Example

Example:To set the default shell to the tcsh shell.

useradd D s /bin/tcsh

The file that contains the useradd default values is/etc/default/useradd

Remember that you need to use the n option to havethe default group option to work in Redhat.

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UserManagement: usermodUserManagement: usermod

The usermod command allows you to modify a usersaccount.

Command Format: usermod [options] usernameOptions-c "comment" Comment field-d /home/user change home directory-m create home directory-u uid specify new uid-g group chnage primary gid-l username change username-G group1, secondary groups-s /bin/shell specify new default shell4/6/20114/6/2011


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UserManagement: usermodUserManagement: usermod

The usermod also allows you to lock and unlockaccounts.

Command Format: usermod [options] username

Options-L Lock the account

-U Unlock the account

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Usermod ExampleUsermod Example

Example:To change the uid of the user bob

usermod u 550 bob

This will also change all of the uids of the files of theuser bob, to the new ones, if they are in the home

directory. To change any that are out side thehomedirectory, you would use the find command (with theexec option).

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UserManagement: userdelUserManagement: userdel

Userdel will delete a user from the /etc/passwd file andthe /etc/shadow file.

Command Format: userdel [option] usernameOption-r Delete home directory.

Example:You want to delete the user named bobuserdel r bob

This will delete his home directory as well.4/6/20114/6/2011

B i UNIX C dB i UNIX C d


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Basic UNIX CommandsBasic UNIX Commands

unameuname Displays the name of the current operatingDisplays the name of the current operatingsystemsystem

date Displays the date and time

cal Displays a calendar for the current month and year.

ls Displays the directory listing

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Command Line SyntaxCommand Line Syntax

command option(s) argument(s)command option(s) argument(s)

CommandCommand Executable commandExecutable command

OptionOption How the command will be ranHow the command will be ran

ArgumentArgument The file, directory or text youThe file, directory or text you

are utilizing for the commandare utilizing for the command

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Control CharactersControl Characters

Control Characters perform specific tasksControl Characters perform specific tasksat the command lineat the command line

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Viewing Online DocumentationViewing Online Documentation

The online UNIX reference manuals provide aThe online UNIX reference manuals provide adetailed description of command and examples ofdetailed description of command and examples ofhow they are usedhow they are usedCommand:

Result:

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S lli h M PS lli h M P


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Scrolling the Man PagesScrolling the Man Pages

Keys used to control the scrolling capabilities in theKeys used to control the scrolling capabilities in the

manualmanual..

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S hi fS hi f


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Searching forman pagesSearching forman pages

To list the online manuals that are availableTo list the online manuals that are availableyou can use theyou can use the kk option. This will allow youoption. This will allow youlist all of the manuals in reference to thelist all of the manuals in reference to theparameter of your command.parameter of your command.

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D t i i C t UD t i i C t U


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Determining Current UsersDetermining Current Users

TheThe whowhologged in users and whatlogged in users and whatsessions they are currently utilizing onsessions they are currently utilizing onthe server.the server.

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Id tif i UId tif i U


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Identifying a UserIdentifying a User

TheThe who am iwho am i command allows you to identifycommand allows you to identifywho you are logged in as.who you are logged in as.

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Id tif i U G D t ilId tif i U G D t il


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Identifying UserGroupDetailsIdentifying UserGroupDetails

Use theUse the idid command to identify the usercommand to identify the userID and group IDID and group ID

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P d C dP d C d


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Passwd CommandPasswd Command

The password command will assign a password to anaccount.

Command Format: passwd [option] username

Option-l Lock the account-u Unlock the account

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P d E lP d E l


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Passwd ExamplesPasswd Examples

You want to lock the bob account.passwd l bob

You want to change or set bob's passwordasswd bob

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/ t // t /


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/etc/group/etc/group

This is the file that contains the names of the groups,the gid associated with the group, and the groupsmembers.

bin:x:1:root,bin,daemon

Group:password:group members

/etc/gshadow holds passwords for the /etc/group file.This is not a popular function. But can be set with thegpasswd command.

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GroupManagement: groupmodGroupManagement: groupmod

You can modify an existing group with the groupmodcommand.

Command Format: groupmod [option] group

Option-g gid change the gid-n name change the group name to name

ExampleTo change the group name from web to accountgroupmod n account web4/6/20114/6/2011

G M n gement g delG M n gement g del


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GroupManagement: groupdelGroupManagement: groupdel

To delete a group from the /etc/group file and fromthe system, use the groupdel command.

Command Format: groupdel group

ExampleTo delete the account group.groupdel account

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Password Aging:Password Aging: chagechage


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PasswordAging:PasswordAging: chagechage

The chage command will set password aging parameters

Command Format: chage [options] user-l displays current settings.-m # minimum days between password changes-E Set expiry date mm/dd/yyyy-M # max days a password is valid

-W # number of days for warning of password change

ExampleTo set the expiry date of the user bobchage E 05/10/2002 bob4/6/20114/6/2011

Initialization FilesInitialization Files


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Two sets of initialization files:Global Set for all usersLocal Allows for the user to customize their

environment.

Global Local/etc/profile ~/.bash_profile

/etc/bashrc ~/.bashrc

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Processing order

/etc/profile

~/.bash_profile

~/.bashrc/etc/bashrc

This is fuzzy, as~.bashrc calls/etc/bashrc

If you start a sub shell~/.bashrc/etc/bashrc

Processed only once, per login

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/etc/skel/etc/skel

If you want to modify the initial .bash_profile and.bashrc files that will be copied into the users

directory, they are located in the /etc/skel directory.

You can create multiple skel directories, if you findthat you find that users need customized initializationfiles, based on group needs with the k option in the

useradd command.

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Module : SystemModule : System

SecuritySecurityReview ofPermissionsReview ofPermissions

S and t bitsS and t bits

Review of Chown, chmod,Review of Chown, chmod,umaskumask

The syslog daemonThe syslog daemon4/6/20114/6/2011

Users and GroupsUsers and Groups


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Users andGroupsUsers andGroups

Talk about users and groups

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Command: lsCommand: ls ll


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Command: lsCommand: ls--ll

total 6drwxr-xr-x 3 steve staff ch1

drwxr-xr-x 3 steve staff ch2


-rw-r--r-- 1 steve staff fullnotes

-rw-r--r-- 1 steve staff outline

d rwx r-x r-xFile TypeD Directory- Regular File

UsersPermissions

GroupPermissions

OthersPermissions

User (owner) Group File/dir name

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File Security: PermissionsFile Security: Permissions


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File permissions determine how users can use files andtraverse directories on the server.

Three sets of permissions:User- Owner of the file/ directoryGroup- A grouping of usersOther- (Public) Anyone expect for the owner andmembers of the group the file/dir belongs to

Three types of permissions:r- Read

w- Write

x- Execute

- Norights

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File Rights:rFile can be read or copied

w File can be modifiedx File can be executed (run), binary or shell scripts- No rights to file

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File PermissionsFile Permissions


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File PermissionsFile Permissions

File Permissions:--x You can execute only *-w- You can modify only *

r-- You can read only-wx You can modify and execute *r-x You can read and executerw- You can read and modifyrwx You can read,modify and execute

If you do not have read rights to a file you cannot copy it,But you can move it!

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Directory Rights:rDirectory contents can be listed with lsw Files can be add or deletedx Access to directory is granted- No rights to directory

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Directory PermissionsDirectory Permissions


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Directory PermissionsDirectory Permissions

Directory Permissions:--x You have access but can't list, delete or create *-w- Cannot do anythingr-- You can list the directory contents only *r-x You can list and travel through the directoryrw- You can list the directory contents only *-wx You can add or delete files, but can't list them,

you can travel through the directoryrwx You can list, add, delete and travel through thedirectory

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PermissionsPermissions


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PermissionsPermissions

Permissions are processed in the following way:

Every user has a uid numberEvery group has a gid numberTo find out your uid/gid useThe id command.

$ iduid=1001(steve) gid=10(staff)

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total 6drwxr-xr-x 3 steve staff ch1



-rw-r--r-- 1 steve staff fullnotes

-rw-r--r-- 1 steve staff outline

d rwx r-x r-xFile TypeD Directory- Regular File

UsersPermissions

GroupPermissions

OthersPermissions

User (owner) Group File/dir name

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Changing Permissions: chmodChanging Permissions: chmod


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Changing file and directory permissions is done throughchmod. You have to own the file or directory in order to beable to change its permissions.

Two ways to use chmod: symbolic modeCommand Format:

chmod [option] [who][op-code][permission] fileOptions-R Recursively make changes

who op-code permissionu user = set rreadggroup + add w writeo other - remove x executea

all

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Chmod: Symbolic ModeChmod: Symbolic Mode


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Chmod: SymbolicModeChmod: SymbolicMode

Examples:

$ cd;touch changeme

To add execute permissions to the file use the command:$ chmod u+x changeme

You can also combine options in the command$ chmod u-x,o-r changeme

In symbolic mode you can specify what permissions youwant to have changed without knowing what permissionsare already set.

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Octal Mode:Command Format: chmod [option] [octal numbers] file

Option-R Recursively make changesOctal numbers:

User Group Otherr=4 r=4 r=4

w=2 w=2 w=2x=1 x=1 x=1

(User total x 100)+(Group total x10) +(Other total)= Octal4/6/20114/6/2011

Chmod ExamplesChmod Examples


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Chmod ExamplesChmod Examples

Examples:

$ cd;touch changeme

$ chmod 744 changeme

$ chmod 640 changeme

When you change permissions in octal mode, you mustspecify all of the permissions.

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New Permissions Files: s bitNew Permissions Files: s bit


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New Permissions Files: s bitNew Permissions Files: s bit

The s bit can be applied to the user and the groupportions. The s bit is used when the file is executed.

When the s bit is applied to the user part of thepermissions, it means "run this program as if youare the user"Look at /usr/bin/passwd

When the s bit is applied to the group part of thepermissions, it means "run this program as if youare a member of the group"Look at /usr/bin/wall4/6/20114/6/2011

New Permissions Dir: s bitNew Permissions Dir: s bit


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New Permissions Dir: s bitNew Permissions Dir: s bit

The s bit can be applied to the group portion of adirectories permissions. It has now effect if it isSet on the user or other portions.

When a file is saved in a directory with the s bit seton the group,its group ownership will be set to thedirectories group owner.

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Setting the s bitSetting the s bit


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To set the s bit for the user, you can use either thesymbolic method or the octal method.

Symbolic method:

Setting it for the userchmod u+s runme.sh

Setting it for the groupchmod s+g runme.sh

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To set the s bit in the octal mode, we add a new set:Special User Group Other

Special:4 = user s bit in binary: 1002 = group s bit in binary: 010

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Setting the s bit: OctalSetting the s bit: Octal


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Setting the s bit: OctalSetting the s bit: Octal

Octal setting user s bit on a filechmod 4755 runme.sh

Octal setting the group s bit on a filechmod 2755 runme.sh

Setting both user and group s bits on a file

chmod 6755 runme.sh

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The "sticky" bitThe "sticky" bit


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The sticky bitThe sticky bit

The sticky bit is applied only to a directory and hasthe effect of only allowing the owner, directory owner

or root the ability to delete or remove files in thatdirectory.Look at /tmp

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Setting the t bitSetting the t bit


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To set the t bit for the user, you can use either thesymbolic method or the octal method.

Symbolic method:

chmod o+t /data

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To set the t bit in the octal mode, we use it on the newset:Special User Group Other

Special:1 = t bit Binary 001

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Setting the t bit: OctalSetting the t bit: Octal


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Setting the t bit: OctalSetting the t bit: Octal

Octal setting user t bit on a directory

mkdir /public

chmod 1777 /public

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The special setThe special set


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The special setThe special set

You can combine the special bits, if you need to.

For Example:You want every file created in the /public to belong tothe group html and to have the sticky bit, so that onlythe owner, directory owner or root can delete files in

that directory.

chown steve:html /publicchmod 3777 /public

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Permissions: DefaultsPermissions: Defaults


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Permissions: DefaultsPermissions: Defaults

When you create a file or directory it is given defaultpermissions.Defaults:

Files rw- rw- rw- (666)Dir. rwx rwx rwx (777)

These defaults can be changed with the umask command.Command Format: umask [octal number]

User Group Otherr=4 r=4 r=4

w=2 w=2 w=2

x=1 x=1 x=1

(User total x 100)+(Group total x10) +(Other total)= Octal4/6/20114/6/2011

Permissions: umaskPermissions: umask


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To view your current umask filter:$ umask022 The OS creates this for you

$ touch changeme

Default permissions: rw- rw- rw- (666)Umask filter: --- -w- -w- (022)

Result rw- r- r- (644)

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Umask only takes away rights, does not add them. Youcan set your own umask to suit your security needs.

Example:$ umask 027 Files: Allows all default rights to the

owner/creator, gives group usersread only rights, and no rights toeveryone else to newly created files.

Dir: Allows all rights to users, givesread and execute permissions togroup users and no permissions toeveryone else to newly createddirectories.

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Chown: Changing OwnershipChown: Changing Ownership


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C o C a g g O e s pC o C a g g O e s p

chown changes the ownership of a file or directory.

Command Format: chown [-options] file-R recursively change files

Example:$ touch changeme$ chown root changeme

$ ls l changeme-rw-r--r-- 1 root staff 0 Jan 6 15:19 changeme

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Chown AgainChown Again


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gg

To change a files ownership and group assignment at thesame time use the chown command.

Command Format: chown user:group [option] file

Or chown user.group [option] fileOr chown .group [option] file

-R Recursively change assignments

Example:$ touch allchange$ chown root:web allchange$ ls l allchange-rw-r--r-- 1 root web 0 Jan 6 15:51 allchange4/6/20114/6/2011

chgrpchgrp


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g pg p

To change the group assignment of a file or directory,use the chgrp command.

Command Format: chgrp [options] file-R recursively change files

Example:$ touch mygroupfile

$ chgrp web mygroupfile$ ls l mygroupfile-rw-r--r-- 1 steve web 0 Jan 6 15:46 mygroupfile

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Module 4: CommandModule 4: Command

ReviewReview

Cp, mv, touch,Cp, mv, touch,*,?,[],{},>,,


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yy

Lists the files and directories in theLists the files and directories in thedirectory specifieddirectory specified

Command Format: ls [Command Format: ls [--options] [pathname]options] [pathname]

Options:Options:

--aa Display hidden filesDisplay hidden files

--FF Display with file types * / @Display with file types * / @

--ll Display long formDisplay long form

--RR List files in subdirectoriesList files in subdirectories

--bb List hidden charactersList hidden characters

--dd List directory names but not the contentsList directory names but not the contents4/6/20114/6/2011

Commands: cat ConcatenateCommands: cat Concatenate


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Cat will display text files on the screen.

Command Format: cat filename

Example:

$ cat /etc/passwd

$ cat /etc/passwd /etc/groups > sysfiles.txt

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Commands: touchCommands: touch


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Touch allows you to create an empty file. If the filealready exists, then touch will update the last accesstime stamp.

Command Format: touch filename

Examples:$ cd$ touch test$ touch test1 test2 test3

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Commands: cpCommands: cp


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pp

Copy files and or directories from one location to another

Command Format: cp [option] source destination

-i Confirm overwrite-r Recursive copy used in directory coping-p Preserve all information (root)Source Can be files or directoriesDestination Can be filenames or directories

Example:# cp /home/steve/readme.txt /root/# cp p /home/steve/readme.txt /root/readme2.txt

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Commands: mvCommands: mv


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Move or rename files or directories.

Command Format: mv [option] source destination

-i Confirm overwrite-f Force MoveSource Can be a file or directoryDestination Can be file or directory

Examples:$ cd;touch waffle;mkdir breakfast$ mv waffle eggs$ mv eggs breakfast

$ mv breakfast lunch

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Commands: rmCommands: rm


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Delete files (and directories) with rm.

Command Format: rm [option] filename

-i Confirm deletion-r Remove Directory and its contents-f Force removal of files with no write permission

Examples:

$ cd;touch babar;mkdir house;touch house/chair$ rm i babar$ rm r house4/6/20114/6/2011

Commands: mkdirCommands: mkdir


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Mkdir creates an empty directory.

Command Format: mkdir [option] directory_name

-p Create directories within directories-m set access permissions

Examples:$ cd

$ mkdir m 777 coffee$ mkdir beans$ ls -l

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Commands: rmdirCommands: rmdir


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The rmdir command only deletes empty directories.

Command Format: rmdir directory_name

Example:

$ cd;mkdir tempdir

$ rm tempdirIf the directory contained files and you still wanted todelete it, remember to use the rm rf command

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MetacharactersMetacharacters


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* Asterisk? Question Mark

[] Brackets; Semi-colon

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Metacharacters: AsteriskMetacharacters: Asterisk


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*Wildcard Character. Match zero or more characters.

Slang: Splat,Star

Example:$ cd /usr/bin$ ls b* List all the files that start with b

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Metacharacters: Question MarkMetacharacters: Question Mark


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?Match a single character.Slang: Query

Example

$ cd /usr/bin

$ lsp?? List all the files that start with pbut contain three characters

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Metacharacters: BracketsMetacharacters: Brackets


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[]Square BracketsMatch a single character with either a range [a-c] or

set [abc] ([bca] is the equivalent of [abc]) [A-z] for upperand lower case matching

Example:$ cd /usr/bin

$ ls[ab]* List all the files that start withletters a or b

$ ls[!ab]* Using the ! Says, don't match thesecharacters4/6/20114/6/2011


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Metacharacters: Semi ColonMetacharacters: Semi Colon


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Allows for multiple commands on one line

Command Format:Command;Command;Command

Example:$ date;pwdSun Oct14 19:43:47 ADT 2001/usr/bin

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Redirection: > < >Redirection: > < >


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Input to a command can come from the keyboard or byusing a can put put into a file or with a >> can beAppended to the end of a file.

Error messages are usually displayed on the screen, butBy using a 2> can be redirected to a file.

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Redirection:


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Take the contents of a file and uses it as if it were inputfrom the keyboard.

Command Format: command < file

Examples:

$ ls > lists

$ sort r < lists

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Redirection: >Redirection: >


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Direct any error messages into a file.

Command Format: command 2> file

Example:$ cd$ find /home name ls 2> err.log$ cat err.log

If err.log doesnt exist, it will be created and the outputwill be put into the file.

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Redirection: >>Redirection: >>


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Append any error messages into a file.

Command Format: command 2>> file

Example:

$ cd$ ls /usr/rack 2> err.log$ ls /bix 2>> err.log$ cat err.log

/usr/rack: No such file or directory/bix: No such file or directory

If err.log doesnt exist, it will be created and the outputwill be put into the file. The second error will be

appended to the err.log file

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Multiple RedirectionMultiple Redirection


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You can use all redirectors if you want to.

Command Format: command > file1 2> file2

Example:$ cd$ find / -name "*sh" > list.txt 2> err.log

If the command has some output, then it will be placedin the list.txt file, but if the command has an error, thenit will be placed in the err.log file.The append notation could be used as well (>>)4/6/20114/6/2011

Redirecting: MiscRedirecting: Misc


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When you run a command, three files are opened and areassociated with that command.

They Are: Standard Input (STDIN)=0Standard Output (STDOUT)=1Standard Error (STDERR)=2

So when you redirect input or output, you are manipulatingthese files. When you want to redirect output you use the

form: command n> file.To redirect output coming from both STDOUT and STDERRinto the same file you would use the form:

command > file 2>&1 or

command >> file 2>&1

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Redirecting: Discarding outputRedirecting: Discarding output


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Sometimes you may not want output from a command tobe displayed on the screen and we may not want itsaved to a file. You can send output to a special file

called /dev/null which discards any output it receives.It takes the form of:command > /dev/null orcommand > /dev/null 2>&1 orcommand 2> /dev/null

Example:$ $ find / -name "*sh" > list.txt 2> /dev/null

This completes the command but all output is sent to the

bit bucket

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Piping: |Piping: |


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Piping takes the output of one command and uses it asinput for another command.

Command Format: command | command

Example:

$ ls /usr/bin | more

$ ls /usr/bin | sort r | more

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Splitting Direction with :teeSplitting Direction with :tee


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Send the output of a command to the screen and to a file.Commonly used with the pipe command

Command Format: tee [option] filename-a Append to a file

Examples:

$ ls /sbin | tee sbin.list$ date | tee a sbin.list$ date | tee date.txt

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BashAliasesBashAliases


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bash: Aliasesbash: Aliases


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Aliases allow for:Creation of CommandsCreation of alternate forms of a command

Multiple commands rolled into oneCan be added to the .bashrc, so they can be availiable atlogin. They dont transfer to sub shells.

Command Format: alias command=new_command

Examples:$ alias ls='ls F'$ alias c=clear$ alias copy='cp i'$ alias home='cd;ls'

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bash: Aliasesbash: Aliases


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To view the current aliases in use the alias command.

Command Format: alias

To delete an alias use the unalias command.Command Format: unalias alias

Example:$ unalias ls

To temporarily bypass an alias use the back slash \

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Bash Command SubstitutionBash Command Substitution


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Bash offers two types of command substitution

Using the back quotes ``

Using the brackets ()

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BackQuotesBackQuotes


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There are some special characters to help puttinginformation into variables.Single back quotes ` ` When a command is put

between back quotes, its output is used as thevariables informationExample:$ DT=`date`$ echo $DT

Tue Oct 23 19:38:38 ADT 2001

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BracketsBrackets


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There are some special characters to help puttinginformation into variables.Single back quotes ` ` When a command is put

between back quotes, its output is used as thevariables informationExample:$ DT2=$(date)$ echo $DT2

Tue Oct 23 19:38:38 ADT 2001

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Single QuotesSingle Quotes


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Single quotes ' ' dont allow for any command or variablesubstitution.

$WO='uname n'$ echo $WO

$ WO=`uname n`$ echo ' this computer is named $WO and thetime is `date` 'this computer is named $WO and the time is Tue Oct 2319:48:51 ADT 2001

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Double QuotesDouble Quotes


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Double quotes allow for commands and variables to beused within the text

$ echo " this computer is named $WO and the

time is `date` "

this computer is named bob and the time is Tue Oct 2319:48:51 ADT 2001

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Module 5Module 5

Grep, cut, expand, fmt, join,Grep, cut, expand, fmt, join,nl, od,paste, pr, split, tac, tr,nl, od,paste, pr, split, tac, tr,

xargs, sedxargs, sed

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grepgrep


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Searching in files: GrepSearching in files: Grep


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Grep allows you to search files for text. Grep can alsoworks with other commands as a filter.

Command Format: grep [options] pattern filename

-i ignore case-v Search for all patterns that do not match-w Use pattern as a word-n print line number

Examples:$ grep root /etc/passwdroot:x:0:1:Super-User:/:/sbin/sh

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Grep WildcardsGrep Wildcards


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Wildcards^pattern Match only if pattern is at the start of a linePattern$ Match only if pattern is at the end of a line

. Match exactly one character[list] match exactly one character in list[^list] Don't match any character in list.* Match 1 or more characters* Repeat previous character

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Grep ExamplesGrep Examples


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cat test.txtabcabbc

acabghgtcbilabagkcxbcdvbc

$ grep ab*c test.txt

$ grep ab.*c test.txt

$ grep .*g test.txt

$ grep ^c test.txt

$ grep k$ test.txt

$ grep [^ad] test.txt4/6/20114/6/2011

cutcut


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The cut command allows you to print a selected columnof a text file.

Command Format: cut [option] fileOption-c print the character in column #-d set field delimiter (default-f# print field number

Example:To list the second field in the /etc/passwd filecut d : -f 5 /etc/passwd4/6/20114/6/2011

expandexpand


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Expand replaces tabs with spaces. The default is8 spaces to a tab. This does not affect the originalfile.

Command Format: expand [options] file-t # replace the tab with # of spaces.

Example:

expand t 2 list.txt

Expand t 2 list.txt > newlist.txt4/6/20114/6/2011

fmtfmt


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The fmt command formats paragraphs to a uniformlength. By default, fmt will reformat each line of aparagraph to a length of 75 lines

Command Format: fmt [option] fileOption-u Set one space between words, two spaces

between sentences.-w set line length default is 75 characters.Example

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tactac


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Tac is the cat command in reverse.

Command Format: tac file

Example: tac grinch.txt

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joinjoin


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The join command allows you to two files that share acommon field.

Command Format: join [option] file1 file2Option-j1 field Use field #(column) in file one-j2 field Use field #(column) in file two-j field Use this field for both files

Example:join j11 j2 2 joiner1.txt joiner2.txt

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nlnl


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The nl command counts the number of lines in afile, but will adhere to certain formatting rules.The \:\:\: characters signify that the next text willbe a header.The \:\: characters signify the the following will bethe body.The \: characters signify that the next set will the

footer.

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nlnl


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Command Format: nl [option] fileOption-b type Body numbering options

-h type Header number options-f type Footer numbering optionsType:a Number all linesn Do not number linest Number only non empty linespPATTERN Number only lines that contain PATTERN

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nl examplenl example


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This counts only the lines in the body section that containthe pattern line2

nl b pline2 nltest.txt

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odod


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The od command allows you to view files in variousformats. This is useful for viewing binary files.

Command Format: od [option] fileOption-t type Type of output to be displayed

Type: a Named Characterc backslashx Hexidecimalo Octal

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odod


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Examples:

od t c od.txt

0000000 a h \n b l a h \n \n0000011

od t x od.txt0000000 620a6861 0a68616c 0000000a0000011

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pastepaste


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The paste command connects two or more files vertically.

Command Format: paste [option] file1 file2

-d'char' Separate columns by 'char'-s Merge, moving all of the lines of the file into

one line, and in the next file move all of the

lines into one line and place it below thefirst line.

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prpr


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Print a file with headers and page fills. The headerconsists of the date, time, filename and page number.

Command Format: pr [option] file

Option-d Double space-h 'header' Use 'header' instead of the filename in the

header section

-l # Set the number of lines per page-o # Set the left margin

Example:pr grinch.txt

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splitsplit


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Chunk up a file into separate files. The extensions of the newfiles will be in the form of aa, ab, ac

Command Format: split [option] file splitfilename-n # Split the file into # lines per segment-b # Size in bytes,

if you use #k it will be in kilobytesif you use #m it will be in megabytes

Example: split n 50 grinch.txt grinsplit_

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trtr


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Translate (or replace) characters from one string to thesecond string specified.

Command format: tr [option] string1 string2Option-d Delete characters from string1 from the output-s Delet repeated characters from string1

Example:tr Gg VQ < grinch.txt

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xargsxargs


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Xargs takes the ouput from a command and treats it as alist for another command to process.

Command Format: xargs [option] commandOption-p Prompt before executing the command

Example:

find . type f | xargs grep Grinch

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sedsed


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Sed is a non interactive text editor. You can edit filesthrough a sed command or through a sed script.

Command Format: sed [option] 'command' file

Option-f file Take commands from file-e cmd Next argument is a command (for

multiple commands in one sedcommand)

-g All substitutions are global-n Print only what the print cmd tells you to4/6/20114/6/2011

sedsed


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Editing Commands:

'Address'd Delete a line or lines

'Address'p print a line or lines'/string/r file' Read a files/string1/string2/ Substitute one string for another

Where 'Address' can be a line number or a range of linesto be edited.

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Sed: Examples: PrintingSed: Examples: Printing


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To print a range of text.

sed n '5,15p' grinch.txt

Print the lines that contain the pattern Christmas

sed n '/Christmas/p' grinch.txt

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Sed: Examples: SubstitutingSed: Examples: Substituting


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To substitute a pattern, use the 's/string1/string2/' cmd

sed 's/Grinch/Jimmy/' grinch.txt

To add the new string to the old string

sed 's/Grinch/Jimmy&/' grinch.txt

To make changes globally. If there are paragraphs

sed 's/Grinch/Jimmy/s' grinch.txt4/6/20114/6/2011

Sed: Examples: DeletingSed: Examples: Deleting


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To delete a range of text.

sed '5,15d' grinch.txt

Delete the lines that contain the pattern Christmas

sed '/Christmas/d' grinch.txt

Don't delete lines 10,20

sed '10,20!d' grinch.txt4/6/20114/6/2011

Sed: Examples: Insert FileSed: Examples: Insert File


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To insert file aftermatch is found.

sed '/Grinch/r insert.txt' grinch.txt

Print the lines that contain the pattern Christmas

sed n '/Christmas/p' grinch.txt

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Module 6Module 6

Linux File SystemLinux File System

fdisk, mkfs, mkswap, df, du,fdisk, mkfs, mkswap, df, du,

fsck, mount, umount, fuser,fsck, mount, umount, fuser,fstab, mtabfstab, mtab

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Module 7Module 7

Disk QuotasDisk Quotas

Quota, quotaon, quotaoff,Quota, quotaon, quotaoff,

quotacheck, edquota,quotacheck, edquota,repquotarepquota

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Module 8Module 8

Process ControlProcess Control

Ps, top, pstree, kill, &, fg, bg,Ps, top, pstree, kill, &, fg, bg,

jobs, nice, renicejobs, nice, renice

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ProcessesProcesses


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Every programme/ action/ task creates a process.Each process gets a unique number called a PID.Five types of processes:

Daemon: Started by the kernel and wait for actionParent: First process to be run, if it spawns any

processes then they are its children. I.e. Terminal sessionChild: A process run from another processOrphan: A process that doesnt end before its

parent. Sent to the init process to be shutdownZombie: A lost process. Loses its parent and canonly be removed by a reboot.

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pstreepstree


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Pstree allows you to see how processes are related ordependent on each other. It is presented in a humanreadable form.

Command Format: pstree [option] [pid|user]Optionsa Show cmd line args used to execute the processG View the tree using vt100 charactersn Sort by pid number instead of alphap Include PIDs in output

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Processes: pstreeProcesses: pstree


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The ps command allows you to view the current processesrunning on the system.

Command Format: ps [options]

-a View all processes-u User format , and start time of process-f Display full listing-x Include processes without controlling

terminals-U user Display users processes-G group Display groups processes

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PSPS


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Since ps screens can be long its useful to combine it withsome other commands, like more and grep.

Example:

$ ps aux | moreUSER PID %CPU %MEM VSZ RSS TTY STAT START TIME COMMAND

root 1 0.0 0.2 1412 520 ? S Mar28 0:04 init [5]

root 2 0.0 0.0 0 0 ? SW Mar28 0:00 [keventd]

root 3 0.0 0.0 0 0 ? SW Mar28 0:00 [kapm-idled]

Or if you want to search for a certain process$ ps aux | grep initroot 1 0.0 0.2 1412 520 ? S Mar28 0:04 init [5]

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toptop


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Top is like ps, but it will refesh its listing to keep thedisplay current. Top laso displays, memory and swapusage. Uptime, load and cpu status are also displayed.

Command Format: top [option]Optionsb Run in batch mode. Creates a snap shot.d Set the refresh rate in seconds.

n # refresh # of times then exitq Run with no delay, should not run as roots Disable interactive commands

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Top: Interactive commandsTop: Interactive commands


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When top is running, you can use it to modify processes.

Commands:

h or ? Display the help screenk Kill a processn Change the number of processes to showr Renice a process (change it's priority)u Show a specific userSpace Update Displayq quit top

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pgreppgrep


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Pgrep combines ps and grep into one command. This isnew to Solaris 7 & 8.

Command Format: pgrep [options] string-l Long listing-U Users process-G Groups process

Example:$ pgrep l init1 init

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Job ControlJob Control


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Unix allows you to be able to run multiple programsat the same time on the same terminal. This isespecially useful if you are working from a command

line interface. If you are using a window manager likeKDE/CDE or Gnome then jobs can only be controllingfrom the terminal window that they were startedfrom.

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Commands:jobs Displays what jobs are running and itsID

bg %n Puts a job into the background (n= jobid)fg %n Brings a job back to the foregroundkill %n Ends the jobControl C Aborts the foreground job

Control Z Suspends the foreground job& Used at the end of a command to put it

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Examples:$ find / -name core > /tmp/clist 2> /tmp/c.err &Look for all files named core, put the result in the file/tmp/clist, if there are any errors list them in /tmp/c.errand with the & run it in the background.[1] 2372$ jobs[1] + Running find / -name core > /tmp/clist

Job ID Status Command

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$ ls R / > /dev/null 2> /dev/null &[2] 2385$ jobs[2] + Running ls -R / > /dev/null 2> /dev/null &

[1] - Running find / -name core > /tmp/clist 2>

$ fg %1Brings the find job to the foreground$ ^Z(Control Z) suspends the job

$ bg %1Puts the job back to the background$ kill %2Terminates the first job

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Terminating ProcessesTerminating Processes


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When a process stops responding or is out of control, ithas to be terminated.Sending an interupt ( control c) will sometimes terminate

a process.The kill command is another way to end a process,epically if your terminal is locked up and you have to useanother terminal window.

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PkillPkill


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Pkill combines ps and grep with kill to make search forthe process id easier.

Command Format: pkill string

Example:$ pkill find

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nicenice


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The nice command will let you run a command witha lower priority. A processes' priority can range from20 to +19. By default it runs at 0.

The higher the number,the lower the priority.Normal users can adjust a program from 1 to 19

Root can adjust a program from 20 to 19Default adjustment is 10

Command Format: nice [option] commandOptionn -# Adjust the priority to #--4/6/20114/6/2011

nicenice


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The nice co