LPI 101 Ch07 Administration Utilities

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SAIGONLAB 83 Nguyn Th Nh, P9, Q.Tn Bnh, Tp. HCM LPI 102

Chapter7

Administration Utilities


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Objectives

Describe, use man pages and other information Demonstrate how to communicate with users

Identify system defaults

Demonstrate how to find files


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man Pages and the man Command

You can get information about most commands using man.This online help system contains the following information

about each command:

Command name

Synopsis and description

List and definition of all options

Environment and parameters

Relatedcommands are listed at the end of the man page. The

number in parentheses after a command is thesection of the

manual pages


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Table2.1 : manpagesectionsandtheirdescriptions


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man Pages and the man Command

To view a particularsection of the man pages, include thesectionnumber with the man command and the term you are

looking for:

man


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Example

$ man passwdPASSWD(1) User utilities PASSWD(1)

NAME

SYNOPSIS

DESCRIPTION

OPERANDS

EXAMPLE.SEE ALSO

finger(1), login(1), nispasswd(1), crypt(3C), passwd(4)


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Scrolling in Man Pages

Spacebar Move forward one screen

Return Move forward one line

b Move back one screen

f Move forward one screen

q Quit the man command

/string Find forward

n Find the next occurrence of string

h Help more



Searching Man Pages by Keyword

If you are not sure of the command name, use the man

command with -k option

man -kkeyword

Example :$ man -k insert

insque (3)insert/remove an item from queue

remque [insque] (3) - insert/remove an item from queue

wrjpgcom (1)insert text coments into JPG file



Which command use to remove user ?

$ man -k delete

groupdel (8) - Delete a group

rmdir (2) - delete a directory

userdel (8)Delete a user

account and related files



Which command use to modify user ?

$ man -k modify

ar (1)- creat, modify and

extract from archive

...

setpnp (8)- modify Plug and Play

BIOS device resources

usermod (8)- Modify user account

...



Which command use to create user ?

$ man -k create | grep usernewuser (8)update and create new

user in batch

smnpusm (1)creates and mantains SMNPv3 users on a

remote entityuseradd (8)Create a new user or update default new

user information



Manual Entries

Manual pages are mostly stored under /usr/man/ troff/nroffformat manual pages (compressed)

Formatted manual pages (compressed) are usually

temporarily stored under /var/catman/

man can be searched in multiple directories by setting the

MANPATH variable.

MANPATH=/usr/man:/usr/X11R6/man:/usr/share/man

If the MANPATH is not set then man will assume /usr/man



Manual Entries

Manual pages are formatted when needed, and aredisplayed using apager program:

more is generally used by default

Set the PAGER variable to override the default

less is probably now much more suitable, as you can page

backwards, search for strings and patterns, and more

$ export PAGER=less



Related Commands

On most Linux systems (that maintain the "index" or old-fashioned so-called whatis database) you can use the

command whatis to print theshort description of a

command ("synopsis"):

$ whatis man

man (1) - format and display ths on-line manual pages

man (7) - macros to format man pages



Related Commands

If you don't know the actual name of a command, you cansearch for keywords in the synopsis with the commands

man k or its alias apropos

$ apropos manuals

man (1) an interface to the on-line

reference manuals

mdoc.samples (7) tutorial sampler for writing

manuals with -mdoc

You may run makewhatis to rebuild whatis database before

using these commands



infoCommand

Not all man pages are being maintained and are therefore outof date, so info yields more current information.

Some topics treated in info are not discussed in man at all,

info also uses hypertext links, so it is a more powerful utility



Documentation in /usr/doc

Documentation that doesnt fall under man pages and infois usually put into /usr/doc or /usr/share/doc. This directory

can hold a wealth of information :HOWTOs, user guides,

FAQs, READMEs,



Online Documentation

Linux Documentation Project:

http://www.tldp.org

http://www.ibiblio.org/mdw/index.html

http://www.linux.org
http://www.tldp.org/http://www.ibiblio.org/mdw/index.htmlhttp://www.linux.org/http://www.linux.org/http://www.ibiblio.org/mdw/index.htmlhttp://www.tldp.org/



Identifyingthe System

The uname command shows system information; thecommand hostname also identifies the current host. uname

command options are below :

-a All information -v OS version number

-n System name (nodename

on network )

-m Machine hardware

-s OS name -p Processor type

-r OS release number


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System Default Files

Linux stores some command defaults in files in /etc/default directory: Filename same ascommand name

Entries in the filetake the form of environment variable definitions

Details of defaults definedin command manual page

Files are usually edited manually

Example :

# more /etc/default/useradd

GROUP=100

HOME=/home

SHELL=/bin/bash

SKEL=/etc/skel


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Identifying Active Users

History of every login is kept in /var/log/wtmp ,can be shownby the last command

The who command shows who is currently logged on to the

same system, information kept in /var/run/utmp

The whoami and id are used to identify the current user

Most Linux system have a w command, outputs more

information than who command


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Communicating with ActiveUsers

Use write to display a message on a user's terminal Users can disable messages using mesg n command

Root can always write to a user

Write all (wall) will display to all logged-in users Useful for sending out broadcasts

Used by the system shutdown mechanism

Use talk command to set up a two-way dialogue


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Login Prompts

When you log into a Linux system via the command line, youare greeted with a message. The /etc/issue file generates this

message

For users who log inremotely, the /etc/issue.net file contains a

message or system identification to be printed before the login

prompt


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The findCommand

The find command locates files using specified search criteria:find directoriessearch_criteria [action]

find command will search fromdirectories and sub-directories

recursively

find command will output all files that match with

search_criteria


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The findCommand

search_criteria

-namename Finds only flies called name (can use shell wildcards: *, ?)

-username Finds only files owned by user name

-type letter Finds files of specified type: f(plain files), d (dirs), etc.

-mtimen Finds files modifiedn days ago, less than (-n), greaterthan (+n)

-sizen [cK] Finds files of sizen, larger than (+n), smaller than (-n),

c=chars,K=kilobytes (when omitted, 512 block size is

implied)-permmode Find files that matchs the prmission setting ofmode


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The findCommand

action:-print Print filename found, its default

-exec cmd {} \; Executes given command ( filename will

be given in place of {} )

-ok cmd {} \; Executes command but prompts for

confirmation


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Example 1

Search for openwin starting at the /usr directory$ find /usr -name openwin

/usr/openwin

/usr/openwin/bin/openwin

( longlist: $ find /usr -name openwinls )

Search for files ending in tifstarting at the /usr

$ find /usr -name *tif

/usr/openwin/demo/kcms/images/tiff/ireland.tif


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Example 2

Search for core files starting at the users home directory anddelete them :

$ find ~ -name core -exec rm {} \;

Find files larger than 400 blocks (512-byte blocks ) starting at/etc

$ find /etc -size +400


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Example 3

Find files, starting at /etc, which share the same inode number:

$ find /etctype fname *.conf

Find files with open permissions starting at the users homedirectory

$ find ~ -perm 777


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locate Command

On most Linux systems, a database is maintained of all filesin the directory tree. The command locate followed by a

string, will return all files (with their full directory path)

that contain that string. The slocate command, a security

enhanced version of the locate command, is quickly

replacing locate

Create database for locate and slocate

$locate or slocate with optionsu/var/lib/slocate/slocate.db


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Locating Commands

The which command will search from PATH environmentvariable to determine the path of a executed command.

Syntax:

which

Similarly, whereis command will list program source files and

man pages beside the actual executed command. Syntax :

whereis


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Interpreting Files

The file command identifies the contents of any file (filetype) on the Linux system

# file *

feed.dat:ASCII text

myprog: iAPX 386 executable not stripped

myprog.c: C source code

runsys: commands text

Text file can be examined using standard utilities such as

less, more, or vi

Non-ASCII text files can be examined using the od or

strings command


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TEXT PROCESSING

Search text in files with grep family commands: grep,egrep, fgrep

Modify text file with sed (Stream Editor)


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grep Command

Use the grep command to search a file for a specified textstring

If found, grep prints all lines that contain that pattern to

the screen. The grep command can be used as a filter withother commands.

The grep command is case sensitive unless you use withi

option


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grep Command

Command Format :grep [option]stringfilename

Options :

-i Ignore case of string when searching

-v Search for all lines that do not match string


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Example ofgrep

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

$ ls -la | grep -i jun 11

drwxr-xr-x 3 user1 staff 512 Jun 11 13:13 dir4


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Regular Expression Metacharacters


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egrep Command

The egrep command searches the contents of one or morefiles for a pattern using extendedregularexpression

metacharacters.

The egrep command uses all the same options as grep.

Command format:egrep [-options] pattern filename(s)


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fgrep Command

The fgrep command searches a file for a pattern

expressed as afixedstring.

It differs from grep and egrep because it regards all

characters literally, and it does NOT interpret regular

expression metacharacters specified on the command line.

Use fgrep to search for a specific pattern in a file that includes

metacharacter symbols.

Command format:

fgrep option(s) pattern filename(s)


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Using grep

List all directories :# lsl | grep ^d

List al users using bash shell when log in :

# grep bash$ /etc/passwd

List files and directories starting by . :

# lsl | grep \.[^.]


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Filters

Linux traditionally has many utilities that read a stream ofcharacters from stdin, process it in some way.and output their

result to stdout. These utilities are called filters

cat concatenate files and print on the standard output

cut remove sections from each line of files

sort sort lines of text files

head output the first part of files

tail output the last part of files

wc print the number of bytes, words, and lines in files

nl number lines of files


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sed (Stream Editor)

Use the sed program to edit data in files without openingthem in an interactive editor, such as vi.

It allows you to specify edits, or modifications, to a file

from the command line and send the output to the

screen by default.

It is best used to make the same changes across

multiple files quickly. It is also used to read scripts that

administrators need.

Command format:sed [options] [address] command file...[>newfile]



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Used bysed


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sed (Stream Editor)

Delete lines with the d command:

sede /pattern/d filename

sede 4d filename

sede 2,5d filename

sede 5,$d filenamesede $d filename

Search and replace :

sede s/string1/string2/g filename

Multiple edits: usee option

sede/linux/des/abc/ABC/g filename


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Summary

Describe, use man pages and other information

Demonstrate how to communicate with users

Identify system defaults

Demonstrate how to find files

Documents

LPI 101 Ch07 Administration Utilities