RedHat Trainings Day3

7/27/2019 RedHat Trainings Day3

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RH033

Red Hat Linux Essentials

Welcome!


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2

Object ives Day 2

File Editing using vi editor Advanced usage of vi editor Users and Groups Management

Understanding Permissions Linux File system Inodes Links Mounting Media Archives Compression

Using GUI shells ( GNOME & KDE)


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Using Linux File editing tool


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Advanced Uses of the editor

Position the cursor across a file or within a screen

Insert into the file the output of a linux command

Search for text and replace it

Learn advanced reading and saving commands

Configure vi and vim


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Commands

G = go to last line in file

1G = go to first line in file

H = go to first line on screen

M = go to middle line on screen

L = go to last line on screenz = make current line first line on screen

z- = make current line last line on screen

!!date = Inserts the current date and time in to file

!}sort = Sorts the data of your file

!}fmt -66 = formats the data of your file in to 66 column width

Ex mode : Search and Replace command

:%s/big/small

:%s/big/small/g


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Advanced Reading and Saving

:r newfile = writes data from other file to current file

:r !date = writes date to your file

:1,5w xnewfile = writes line 1 to 5 to new file xnewfile

:.,$w ynewfile = writes from current line to end in to new file ynewfile

:1,5w >> xfile = append xfile with line 1 to 5:n = changes to next file

:n! = abandoning changes

:n# = jump to the previous file

:set showmatch = shows the match

:set textwidth=65 = sets the text width to 65 character

:set number = sets the line numbers

( Note : You can use no with set command to unset changes you made )

Ex. :set nonumber = will remove line numbers


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Users and Groups Management


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What is User Account ?

When a computer is used by many people it is usually necessary to

differentiate between the users, for example, so that their private files

can be kept private. This is important even if the computer can only be

used by a single person at a time, as with most computers. Thus, each

user is given a unique username, and that name is used to log in.


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What is Group ?

Is a collection of users which make easy for administrators to perform

the task of administration level when they need to apply permissions

and restrictions with same level to many of the users, then such

permission and restrictions can be applied to related group.


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The root user

The root user: a special administrative account

Same like Adminis t rator we called in Win*

Sometimes called the superuser

root has complete control over the system

An unlimited capacity to damage the system!


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Creating Users

useradd options user - Creates a new user.

-c Assigns full name to user.

-d Uses to define home folders location.

-s Uses to define user's shell. (Use /sbin/nologin for users

you wish to restrict from having shell access). -g Add user to group ( Primary Group )

-G Add user to group ( Secondary Group )

usermod options user - Modifies user account

Same options as useradd.

userdel options user - Deletes user account.

-r : Remove user's home directory.

passwd user - Changes the password of the specified user.

If no user is specified, will change the password of the current user.


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Creating Groups

groupadd group - Creates a group.

groupmod options group - Modifies a group. -n : Rename group

groupdel group - Deletes the specified group.


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Configuration Files

/etc/passwd = file contains user database

/etc/shadow = file contains user password database

/etc/group = file contains group database

/etc/gshadow = file contains group password database


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User Information Commands

Find out who you are

whoami

Find out what groups you belong to

groups, id

Find out who is logged in users, who, w

Login/reboot history

last


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User and Group ID Numbers

User names map to user ID numbers

Group names map to group ID number

Data stored on the hard disk is stored numerically


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Understanding Permissions


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What is Permission ?

Specifies what rights are you granting to users to access the resources

are available in the computer, so that important resources such as files

are protected from unauthorized users.


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Methods of Implementing Permissions

Symbolic Method

Numeric Method


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Permissions- Symbolic Method

Four symbols are used when displaying and applying permissions

r Permission to read a file or list a directorys contents

w Permission to write to a file or create and remove files from adirectory

x Permission to execute a program or change into a directoryand do a long listing of the directory

- no permission ( in place of the r, w, orx )


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Applying Permission with Symbolic Method

chmod command is used to change access modes

Symbolic Method

chmod u+w,go-w somefile file name

( Grants write access to owner but denies it to group and other. )

chmod u=rw somefile file name

( Sets read and write permission to owner, with execute turned off,regardless of the current permission )

chmod +r somefile file name

( Make the file world-readable )

[ Note : +, - and = are operators to add, remove or overwrite thepermission ]


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Four numbers are used when displaying or applying permissions

4 Permission to read a file or list a directorys contents

2 Permission to write to a file or create and remove files from adirectory

1 Permission to execute a program or change into a directoryand do a long listing of the directory

0 no permission ( in place of the 4, 2, or1 )

Permissions- Numeric Method


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Applying Permission with Numeric Method

chmod command is used to change access modes

Numeric Method

chmod 664 somefile file name

( Grants Read and Write access to owner and group but read onlyit to and other. )


( Sets read and write permission to owner, with execute turned off,

with others and group have no permissions )


( Make the file world-readable )


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Others do not have write-

Others have readr

Group has executex

Group does not have write-

Group has readr

Owner has executex

Owner has writew

Others have execute

Owner has readr

x

Permissions


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Understanding File System


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Partition and File System

Disk drives are divided into partitions

Partition are formatted with file system, allows users to store data

Default file system: ext3, the Third Extended Linux File System

Other common file systems:

ext2 and vfat iso9660 ( typically used for CDs)


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Inodes

An inode table contains a list of all files in an ext2 or ext3file system

Directories have inode numbers associated with files.

inodes contain information about the file or directory,including:

Owner, group, permissions, size, location on disk, file type (file ordirectory)

One inode is associated with each file.

The system uses inodes as the definition of a file.

The ls -il command displays the inode number:

80977 drwxr-x--- 1 user user 4096 Mar 19 11:23


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Links

A link is a file that points to another file.

ln creates a link from the original file to a new file in your directory.

Most programs will access the link as if it was the file.

This is similar to a shortcut in Windows.

This allows for aliasing (when two or more names can exist for thesame object)

Easy way to point to a really long absolute pathname or filename


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Using Links

Two types of links can be created

Symbolic ( Soft )

Hard

ln -s main soft( This will create an soft link of file main )

ln main hard

( This will create an hard link of file main )


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Mounting the media

Mounting means making a partition to access from an access pointtypically a folder to store and access data from it.

Commands to mount media

mount /media/floppy = Mounts floppy drive to your computer

mount /media/cdrom = Mounts cdrom drive to your computer

mount /media/Device ID = Mounts usb disk to your computer

Commands to unmount media

umount /media/floppy = Unmounts floppy drive to your computer

umount /media/cdrom = Unmounts cdrom drive to your computer

umount /media/Device ID = Unmounts usb disk to your computer


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Archive Files

Archiving places many files into one target file

Easier to back up, store, and transfer

tar Standard Linux archiving command


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Using Archive files tar command

tar cvf archive_name files..

( To create archive file )

tar tvf archive_name files..

( To display files under archive file )

tar xvf archive_name files..( To extract files from archive file )

tar rvf archive_name files..

( To append archive file )


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File Compression

Results in smaller file size

Text files can be compressed over 75%

tar archives are often compressed


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Compression Utilities

gzip, gunzip

Standard Linux compression utility

Up to 75% compression for text files

bzip2, bunzip2

Newer Linux compression utility

Generally achieves better compression than gzip


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Using Compression

gzip somefile

( To create compressed file )

gunzip somefile

( To uncompress a compressed file )

bzip2 somefile( To create compressed file )

bunzip2 somefile

( To uncompress a compressed file )

Note: - We can use z for gzip andj for bzip2 type of compression with tar


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Using GUI shells ( GNOME & KDE)


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38Simple view of GNOME Desktop


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39Simple view of KDE Desktop


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Questions


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What have we learnt ?

File Editing using vi editorAdvanced usage of vi editor

Users and Groups ManagementUnderstanding PermissionsLinux File system

Inodes

Links

Mounting MediaArchives

CompressionUsing GUI shells ( GNOME & KDE)


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Questions

Day 2 Complete !!!


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Thank You !!!

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