linux notes

Linux Administration (Elective)

UNIT-I System Administration

Managing User Accounts:-

All users must have accounts on the system. Fedora uses the /etc/passwd file to hold

information on user accounts. Each user, regardless of type, has a one-line entry of

account information stored in the /etc/passwd text file.

 

Each account entry contains a username and password field containing an x.

Adding New Users

The command-line approach to adding any user is actually quite simple and can be

accomplished on a single line. In the example shown here, the sysadmin uses the useradd

command to add the new user “king”. The command adduser is a symbolic link to useradd,

so both commands work the same.

#adduser king or

# useradd –c “bcs3 students” -d/home/bcs3 king

The –c option is the full name of the person, -d option is the home directory that we would

want to create for new user.

 

The sysadmin can also use the graphical interface that Fedora provides, as shown in Figure.

 

These are the steps we used to add the same account as shown in the preceding

command, but using the graphical User Manager graphical interface:

1. Launch the Fedora User Manager graphical interface by clicking on the Users and Groups

menu item found in the System, Administration.

2. Click the Add User button to bring up the Add User dialog window.

3. Fill in the form with the appropriate information, as described in the first paragraph in this

section.

4. Click the drop-down Login Shell menu to select the bash shell.

5. Check the Specify User ID box to permit access to the UID dialog.

6. Using the arrows found in the UID dialog, increment the UID to 5413.

7. Click OK to save the settings

           

Note that the user is being manually assigned the UID of 549 because that is her UID on

another system machine that will be connected to this machine

A computer is, by its very nature, a number-oriented machine. It identifies users and

groups by numbers known as the user ID (UID) and group ID (GID).

 

Managing Groups:-

 

Groups can make managing users a lot easier. Rather than having to assign individual

permissions to every user, you can use groups to grant or revoke permissions to a large

number of users quickly and easily. Setting group permissions allows you to set up

workspaces for collaborative working and also to control what devices can be used, such as

external drives or DVD writers. All the groups are listed in /etc/group file.

 

Group Management Tools:-

Fedora provides several command-line tools for managing groups as well as graphical tools.

Many experienced sysadmins prefer the command-line tools because they are quick and

easy to use

 

§ groupadd This command creates and adds a new group.

# groupadd mit

§ groupdel This command removes an existing group.

# groupdel mit.

§ gpasswd This command creates a group password. Every group can have a group

passwo            rd and an administrator. Use the -A argument to assign a user as group

administrator.

# gpasswd -A jack

§ useradd –G The -G argument adds a user to a group during the initial user creation.

(More arguments are used to create a user.)

#useradd jack

§ usermod –G This command enables you to add a user to a group as long as the user

is not logged in at the time.

# usermod -G jack mit

 

The sysadmin can also use the graphical interface that Fedora provides, as shown in

Figure. It is accessed as the Users and Groups item from the System Settings

menu item.

 

You will note that the full set of group commands and options are not available from the

graphical interface, limiting the usefulness of the GUI to a subset of the most frequently

used commands.

Managing Users:-

The sysadmin can manage the users. Users must be created, assigned a UID, provided a home

directory,

provided an initial set of files for their home directory, Fedora provides several commandline

tools for managing users, as well as graphical tools. Many experienced sysadmins prefer

the command-line tools because they are quick and easy to use.

Here are the most commonly used commands for managing users:

 

Useradd: -This command is used to add a new user account to the system. Its options permit

the sysadmin to specify the user’s home directory and initial group or to create the user with

the default home directory.

#useradd -c”student of bcs” -d/home/bcs3 jack

 

Useradd :- G-This command sets the system defaults for creating the user’s home directory,

account expiration date, default group, and command shell. See the specific options in man

useradd. Used without any arguments, it displays the defaults for the system. The default set

of files for a user.

#useradd –G jack

 

Userdel:- This command is used to remove a specified user account from the system.

-r option use to remove user’s from home directory.

#userdel –r jack

 

Usermod:- This command changes several user attributes. The most commonly used

arguments are -s to change the shell and -u to change the UID. No changes can be made

while the user is logged in or running a process.

 

Passwd:- This command updates the authentication tokens used by the password

management system.

 

Managing Permissions:-

 

Under Linux (and Unix), everything in the file system, including directories and devices, is a

file. And every file on your system has an accompanying set of permissions based on

ownership. These permissions form the basis for security under Linux, and designate each

file’s read, write, and execute permission for you, members of your group, and all others on

the system. The ls command’s long-format listing, like this:

 

$ ls -l file

-rw-rw-r-- 1 andrew andrew 0 Nov 11 12:28 file

 

A blank (which is represented by a dash in the preceding example) designates a plain file, d

designates a directory, c designates a character device.

 

Permissions—Read, write, and execute permissions for the owner, group, and all others on

the system.

The owner: - The account that created or owns the file

The group:-The group of users allowed to access the file.

The other user:- The others not in a file’s group.

 

Assigning Permissions

Under Linux, permissions are grouped by owner, group, and others, with read, write, and

execute permission assigned to each, like so:-

 

Owner Group Others

rwx rwx rxw

 

The mnemonic forms of chmod’s options (when used with a plus character, +, to add, or a

minus sign, -, to take away) designate the following:

 

u—Adds or removes user (owner) read, write, or execute permission

g—Adds or removes group read, write, or execute permission

o—Adds or removes read, write, or execute permission for others not in a file’s group

a—Adds or removes read, write, or execute permission for all users

r—Adds or removes read permission

w—Adds or removes write permission

x—Adds or removes execution permission.

 

4 indicates read permission.

2 indicates write permission.

1 indicates execute permission.

In octal notation, the previous example file has a permission setting of 664 (read+write or

4+2, read+write or 4+2, read-only or 4).

 

To restore read and write permission for only you as the owner, use the plus sign and the u

and rw options like so:

 

$ chmod u+rw readme.txt

$ ls -l readme.txt

-rw------- 1 andrew andrew 12 Jan 2 16:48 readme.txt

 

To modify a file’s permissions so that only you, the owner, can read and write a file. Use the

chmod command and a file permission of 600, like this:

$ chmod 600 readme.txt

 

Managing Passwords:-

Passwords are an integral part of Linux security, and they are the most visible part to the User.

An effective password policy is a fundamental part of a good system administration plan.

The policy should cover

. Allowed and forbidden passwords

. Frequency of mandated password changes

. Retrieval or replacement of lost or forgotten passwords

. Password handling by users

The Password File

The password file is /etc/passwd, and it is the database file for all users on the system.

The format of each line is as follows:

username:password:uid:gid:gecos:homedir:shell

passwd command in Linux is used to change the user account passwords. The root user

reserves the privilege to change the password for any user on the system, while a normal user

can only change the account password for his or her own account.

Syntax:

passwd [options] [username]

root]# passwd user1

Processing in passwd command:

1. Verify current user password : Once the user enters passwd command, it prompts

for current user password, which is verified against the password stored in

/etc/shadow file user. The root user can bypass this step and can directly change the

password, so as the forgotten passwords may be recovered.

2. Verify password aging information : In Linux, a user password can be set to expire

after a given period of time. Also, a user can be prohibited to change his/her password

for a period. This password aging information (and the password itself) is stored in a

file /etc/shadow.

3. Change the password : After authentication, the user is prompted to enter the new

password and verify it by retyping the password.

/etc/shadow file: The shadow file is a list of colon separated values with 9 fields, as

shown below:

# cat /etc/shadow

root:*:13121:0:99999:7:::

daemon:*:13121:0:99999:7:::

bin:*:13121:0:99999:7:::

sys:*:13121:0:99999:7:::

sync:*:13121:0:99999:7:::

games:*:13121:0:99999:7:::

man:*:13121:0:99999:7:::

 

· field 1: User name.

· field 2: Encrypted Password.

· field 3: Number of days since January 1, 1970 to when the password was last

changed.

· field 4: Minimum number of days for which password can not be changed. (value 0

means it can be changed anytime).

· field 5: Number of days after password must be changed. (value 99999 means that the

password never expires).

· field 6: Number of days to warn user for expiring password.

· field 7: Number of days after password expires that the account is disabled.

· field 8: The number of days from January 1, 1970 to the date when an account was

disabled.

· field 9: This field is reserved for some possible future use.

passwd options:

· -d, –delete: This option deletes the user password and makes the account passwordless.

· -e, –expire: This option immediately expires the account password and forces the

user to change password on their next login.

· -h, –help: Display help related to the passwd command.

· -i, –inactive INACTIVE_DAYS: This option is followed by an integer, INACTIVE_DAYS, which is

the number of days after the password expires that the account will be deactivated.

· -l, –lock: Lock the password of user.

· -S, –status: Shows the password status

· -u, –unlock: Unlock the password of an account.

Granting System Administrator Privileges to Regular Users:-

It may be necessary for regular users to run a command as if they were the root user.

There are two ways to run commands with root privileges: The first is useful if you are the

super-user and the user; the second if you are not the regular user

The su command spawns a new shell, changing both the UID and GID of the existing

user and automatically changes the environmental variables associated with that user.

This behavior is known as inheriting the environment.

The syntax for the su command is

$ su option username arguments

Note that the working directory has not changed. By executing the following, you become

root and inherit root’s environment:

$ su -

By executing the following, you become that user and inherit the super-user’s environment—

a pretty handy tool

To become another user, specify a different user’s name on the command line:

$ su - other_user

For example, while logged on as a regular user,

$ su – root

the system prompts for a password:

Password:

When the password is entered correctly, the root user’s prompt appears:

#

To return to the regular user’s identity, just type

# exit

This takes you to the regular user’s prompt:

$

This makes sense because no single individual will always be available to perform super-user

functions. The problem is that unix permissions come with an all or nothing authority. Enter

sudo, an application that permits the assignment of one, several, or all of the root-only system

commands.

After it is configured, using sudo is simple. An authorized user merely precedes the

superuser-authority-needed command with the sudo command, like so

$ sudo command

After getting the user’s password, sudo checks the /etc/sudoers file to see whether that user

is authorized to execute that particular command; if so, sudo generates a “ticket” for a

specific length of time that authorizes the use of that command. The user is then prompted for

his password and then the command is run as if root had issued it.

Disk Quotas:-

On large systems with many users, you need to control the amount of disk space a user has

access to. Disk quotas are designed for this purpose. Quotas, managed per each partition, can

be set for both individual users as well as groups.

When files are created, both a user and a group own them; ownership of the files is always

part of the metadata about the files. This makes quotas based on both users and groups easy

to manage. To manage disk quotas, you must have the quota package installed on your

system; it is usually installed by default.

Sysadmins use the family of quota commands, such as quotacheck to initialize the quota

database files, edquota to set and edit user quotas, setquota to configure disk quotas, and

quotaon or quotaoff to control the service.

For example, one line in /etc/fstab shows that quotas are enabled for the /home partition:

/dev/hda5 /home ext3 defaults,usrquota,grpquota 1 1

To initialize disk quotas, the partitions must be remounted. This is easily accomplished with

the following:

# mount -o ro,remount partition_to_be_remounted mount_point

The underlying console tools are:-

· quotaon, quotaoff—Toggles quotas on a partition

· repquota—A summary status report on users and groups

· quotacheck—Updates the status of quotas, it is run after fsck.

· edquota—A very basic quota management command

 

 

 

 

 

 

 

 

 

 

 

UNIT-II Automating Tasks

#Running Services at Bootup:-

Although most people consider a computer to be either on or off, in Fedora there are

a number of states in between. Known as runlevels, they control what system

services are started at bootup. These services are simply applications running in the

background that provide some needed function to your system, such as getting

information from your mouse and sending it to the display; or a service could monitor

the partitions to see whether they have enough free space left on them.

 

1. Beginning the Boot Loading Process

The BIOS is an application stored in a chip on the motherboard that initializes the

hardware on the motherboard. The BIOS gets the system ready to load and run the

software that we recognize as the operating system.

As a last step, the BIOS code looks for a special program known as the boot loader

or boot code. The instructions in this little bit of code tell the BIOS where the Linux

kernel is located, how it should be loaded into memory, and how it should be started.

If all goes well, the BIOS looks for a bootable volume such as a floppy disk, CDROM,

hard drive, RAM disk, or other media and then boots from the first bootable

volume it finds.

2. Loading the Linux Kernel

The Linux kernel loads and runs a process named init, which is also known as the

“father of all processes” because it starts every subsequent process. The init process

looks for a list of instructions in a file named /etc/rc.d/rc.sysinit. That script issues a

number of commands that are run only once—each time the system is turned on.

3. System Services and Runlevels

After finishing with rc.sysinit script during the bootloading process, the init command

uses the Linux system initialization table found in /etc/inittab to boot Fedora to a

specific system state. The state of the system is commonly referred to as its runlevel.

Runlevels determine which of the many available system services are started, as

well as in which order they start.

Runlevel Definitions

. Runlevel 0—Known as “halt,” this runlevel is used to shut down the system.

. Runlevel 1—This is a special runlevel, defined as “single,” which boots Fedora to a

root access shell prompt where only the root user may log in. Networking, X,

and multiuser access are turned off.

. Runlevel 2—This runlevel dictates that Fedora be booted to a console, or text-ased

mode, with multiuser access.

. Runlevel 3—This runlevel is identical to runlevel 2, except that it also starts any

networking services.

. Runlevel 4—This runlevel is undefined, and it can readily be configured to boot

Fedora to a custom system state.

. Runlevel 5—This runlevel boots Fedora to a networking, multiuser state with an

active X session. This is the most common runlevel for home users who want a

graphical interface.

. Runlevel 6—This runlevel is used to reboot the system.

 

4. Booting into the Default Run

Entries in /etc/inittab use a field-based notation that determines the runlevel—when

to execute the process, whether or not the process is executed when booting,

whether or not to wait for the process to complete, and when to execute the process

during booting. The default choices are adequate and need be changed only in

unique circumstances that the average user is not likely to encounter.

The value of the default entry, or the initdefault line in /etc/inittab, determines the

particular system state in which Fedora is when the login prompt is finally presented.

For example:- id:5:initdefault:

#Understanding init Scripts and the Final Stage of Initialization:-

Each /etc/rc.d/init.d script, or init script, contains logic that determines what to do

when receiving a start or stop value. The logic might be a simple switch statement

for execution, as in this example:

case “$1” in

start)

start

;;

stop)

stop

;;

restart)

restart

;;

reload)

reload

;;

status)

rhstatus

;;

condrestart)

[ -f /var/lock/subsys/smb ] && restart || :

;;

*)

echo $”Usage: $0 {start|stop|restart|status|condrestart}”

exit 1

esac

 

Although the scripts can be used to customize the way that the system runs from

power on, absent the replacement of the kernel, this script approach also means that

the system does not have to be halted in total to start, stop, upgrade, or install new

services.

After all the system scripts have been run, your system is configured and all the

necessary system services have been started.

#Controlling Services at Boot with Administrative Tools:-

As the master control file for system startup, /etc/inittab and its corresponding

system of symbolic links control system services. You can manage /etc/inittab and its

symbolic links, using these graphical and nongraphical administrative tools:

· chkconfig—A small script that helps you configure system services.

· ntsysv—A graphical interface for the chkconfig configuration script.

· system-config-services—A full graphical services configuration client. This

application is found in the System Services/Sever settings menu as the

Services menu item.

1.Using the chkconfig Text-Based Command-Line Tool:-

It is an effective, text-based command-line tool that you can use to display,

diagnose, or change the starting or stopping of system services (as available under

/etc/rc.d/init.d) in each runlevel.

For example, to list all services that are turned on in runlevel 5, you can pipe the

output of chkconfig through the grep command like this:

# /sbin/chkconfig --list | grep ‘5:on’ | sort

The chkconfig command can be used to reassign start or stop values for each

runlevel and each service. it alters the scripts that start or stop a service, or it can

report on the status of a service.

2. Ntsysv:-

ntsysv is a graphical interface you can use to access chkconfig and use a graphical

interface.

 

 

 

ntsysv is an ncurses-based interface, meaning that it offers crude, block graphics

and elements you can tab through and select by pressing the spacebar.

The ntsysv utility manages only which services are started in the current runlevel.

Use the --level option to modify other runlevels.

When you have the ntsysv application open, you can scroll through the list of

services and toggle a service on or off by pressing the spacebar on the keyboard.

When finished, use the Tab key to highlight the OK or Cancel button.

3.Using the GUI-Based Service Configuration Tool

These tools provide an easier-to-use interface and don’t require memorization or

lookup of command-line options. Fedora provides its own Service Configuration tool

for the control and administration of services.

You can access the GUI menu selection from the System Settings/Server Settings

menu, and then select Services. The command-line name of this tool is

system-config-services.

 

 

The new Service Configuration tool enables you to select runlevels to edit, displays

all the available services, and provides an explanation of what the service does.

 

#Starting and Stopping Services Manually:-

If you change a configuration file for a system service, it is usually necessary to stop

and restart the service to make it read the new configuration. If you are reconfiguring

the X server, it is often convenient to change from runlevel 5 to runlevel 3 to make

testing easier and then switch back to runlevel 5 to re-enable the graphical login. If a

service is improperly configured, it is easier to stop and restart it until you have it

configured correctly than it is to reboot the entire machine.

There are several ways to manually start or stop services or to change runlevels

while using Fedora. The traditional way to manage a service (as root) is to call the

service’s /etc/rc.d/init.d name on the command line with an appropriate keyword,

such as start, status, or stop. For example, to start the automated nightly update of

the yum RPM package database, call the /etc/rc.d/init.d/yum script like this:

# /etc/rc.d/init.d/yum start

Enabling nightly yum update:                                                                                        [ OK ]

The script executes the proper programs and reports their status. Stopping services

is equally easy, and in fact, you can also check the status of some services by using

the status keyword like this:

# /etc/rc.d/init.d/yum status

Nightly yum update is enabled.

In this example, the yum script reports that the daemon is running. This information

might be useful for other system management tasks.

Using service, you do not have to know the full pathname to the system service; you

need know only the name of the system service you want to manipulate. Using this

approach, the previous yum example looks like this:

 

# service yum start

Nightly yum update is enabled:                                                                                     [ OK ]

Of course, the GUI tools mentioned earlier also have the functionality to start and

stop specific services in your current runlevel. The tool you choose is a matter of

personal preference; a good system administrator is aware of them all.

 

#Scheduling Tasks:-

There are three ways to schedule commands in Fedora, all of which work in different

ways. The first is the at command, which specifies a command to run at a specific

time and date relative to today. The second is the batch command, which is actually

a script that redirects you to the at command with some extra options set so that

your command runs when the system is quiet. The last option is the cron daemon,

which is the Linux way of executing tasks at a given time.

1.Using at and batch to Schedule Tasks for Later

To use at, you need to tell it the time at which you want to run and then press Enter.

You then see a new prompt that starts with at>, and everything you type there—until

you press Ctrl+D comprises the commands you want at to run.

When the designated time arrives, at performs each action individually and in order,

which means later commands can rely on the results of earlier commands.

There is an alternative command, batch, which is really just a shell script that calls at

with a few extra options. These options (-q b -m now, if you were interested) set at to

run on queue b (-q b), mailing the user on completion (-m), and running immediately

(now). The queue part is what is important: Jobs scheduled on queue b are executed

only when the system load falls below 0.8—that is, when the system is not running at

full load. Furthermore, they run with a lower niceness, meaning queue a jobs usually

have a niceness of 2, whereas queue b jobs have a niceness of 4.

Because batch always specifies now as its time, you need not specify your own time;

it simply runs as soon as the system is quiet. Having a default niceness of 4 means

that batched commands get fewer system resources than queue jobs (at’s default)

and fewer system resources than most other programs.

 

2.Using cron to Run Jobs Repeatedly

Instead, there is the crond daemon for running tasks repeatedly based on system—

and user—requests. cron has a similar permissions system to at: Users listed in the

cron.deny file are not allowed to use cron, and users listed in the cron.allow file are.

An empty cron.deny file—the default—means everyone can set jobs. An empty

cron.allow file means that no one (except root) can set jobs.

Scheduling Tasks 251

11There are two types of jobs: system jobs and user jobs. Only root can edit system

jobs, whereas any user whose name appears in cron.allow or does not appear in

cron.deny can run user jobs. System jobs are controlled through the /etc/crontab file,

which by default.

 

 

 

 

 

 

 

 

 

 

UNIT-III System-Monitoring Tools

#Console-Based Monitoring:-

 

Processes can also be controlled at the command line, which is important because

you might sometimes have only a command-line interface. Whenever an application

or command is launched, either from the command line or a clicked icon, the process

that comes from the kernel is assigned an identification number called a process ID

or PID for short.

The process ID you can get a quick list of your processes by using the ps command

like this:

# ps

PID TTY TIME CMD

4242 pts/0 00:00:00 su

4245 pts/0 00:00:00 bash

4286 pts/0 00:00:00 consolehelper-g

4287 pts/0 00:00:00 userhelper

4290 pts/0 00:00:00 system-config-d

4291 pts/0 00:00:00 python2

4293 pts/0 00:00:00 ps

 

 

The /proc directory contains quite a few files—some of which include constantly

updated hardware information (such as battery power levels, and so on). Linux

administrators often pipe the output of ps through a member of the grep family of

commands to display information about a specific program, perhaps like this:

root]# ps aux | grep system-config-display

root 4286 0.0 0.3 13056 3172 pts/0 S 11:57 0:00 system-config-display

This example returns the owner (the user who launched the program) and the PID,

along with other information, such as the percentage of CPU and memory usage,

size of the command (code, data, and stack), time (or date) the command was

launched, and name of the command. Processes can also be queried by PID like

this:

root]# ps 4286

4286 pts/0 S 0:00 system-config-display

You can use the PID to stop a running process by using the shell’s built-in kill

command.

 

# Using the kill Command to Control Processes:-

The kill command is a basic Unix system command. You can communicate with a

running process by entering a command into its interface, such as when you type

into a text editor. But some processes (usually system processes rather than

application processes) run without such an interface, and you need a way to

communicate with them as well, so we use a system of signals. The kill system

accomplishes that by sending a signal to a process, and you can use it to

communicate with any process. The general format of the kill command is:

# kill option PID

A number of signal options can be sent as words or numbers, but most are of

interest only to programmers. One of the most common is

 

# kill PID

This tells the process with PID to stop; you supply the actual PID.

 

# kill -9 PID

is the signal for kill (9 is the number of the SIGKILL signal); use this combination

when the plain kill shown previously does not work.

 

# Using Priority Scheduling and Control:-

The kernel’s primary function is to manage the system resources equitably. It does

this by assigning a priority to each process so that some processes get better access

to system resources and some processes might have to wait longer until their turn

arrives. Priority scheduling can be an important tool in managing a system

supporting critical applications or in a situation in which CPU and RAM usage must

be reserved or allocated for a specific task. Two legacy applications included with

Fedora include the nice and renice commands.

The nice command is used with its -n option, along with an argument in the range of

-20 to 19, in order from highest to lowest priority (the lower the number, the higher

the priority).

For example, to run the gkrellm client with a low priority, use the nice command like

 

this: $ nice -n 12 gkrellm &

The nice command is typically used for disk- or CPU-intensive tasks that might be

obtrusive or cause system slowdown.

The renice command can be used to reset the priority of running processes or

control the priority and scheduling of all processes owned by a user. Regular users

can only numerically increase process priorities with this command, but the root

operator can use the full nice range of scheduling (-20 to 19).

Nearly all graphical process-monitoring tools include some form of process control or

management. Many of the early tools ported to Linux were clones of legacy Unix

utilities. One familiar monitoring (and control) program is top. Based on the ps

command, the top command provides a text-based display of constantly updated

console-based output showing the most CPU-intensive processes currently running.

It can be started like this:

# top

After you press Enter, you see a display. The top command has a few interactive

commands: Pressing h displays the help screen; pressing k prompts you to enter the

pid of a process to kill; pressing n prompts you to enter the pid of a process to

change its nice value. The top man page describes other commands and includes a

detailed description of what all the columns of information top can display actually

represent.

# Graphical Process and System Management Tools:-

 

The GNOME and KDE desktop environments offer a rich set of network and system

monitoring tools. Graphical interface elements, such as menus and buttons, and

graphical output.

Fedora no longer includes the xosview client, which provided load, CPU, memory

and swap usage, disk I/O usage and activity, page swapping information, network

activity, I/O activity, I/O rates, serial port status, and if APM is enabled, the battery

level (such as for a laptop). However, a great replacement is GKrellM, which

provides a much neater interface and a host of additional plugins. You have to use

this command to retrieve GKrellM:

#yum install gkrellm

and after installed it can be found under Applications, System Tools. GKrellM is

shown in Figure.

 

 

 

Some of the graphical system- and process-monitoring tools that come with Fedora

include the following:

 

 

 

1. vncviewer:- AT&T’s open source remote session manager, which can be used to

view and run a remote desktop session locally. This software requires an active,

background, X session on the remote computer.

 

2. gnome-nettool:- A GNOME-developed tool that enables system administrators to

carry out a wide range of diagnostics on network interfaces, including port scanning

and route tracing.

 

3. ethereal:-This graphical network protocol analyzer can be used to save or display

packet data in real time and has intelligent filtering to recognize data signatures or

patterns from a variety of hardware and data captures from third-party data capture

programs, including compressed files. Some protocols include AppleTalk, Andrew

File System (AFS), AOL’s Instant Messenger, various Cisco protocols, and many

more.

 

4. gnome-system-monitor:- This tool is a simple process monitor offering three

views: a list view, a moving graph, and a storage status overview. To access it

choose System, Administration and select the System Monitor entry.

 

# KDE Process and System-Monitoring Tools:-

 

KDE provides several process- and system-monitoring clients. Integrate the KDE

graphical clients into the desktop taskbar by right-clicking on the taskbar and

following the menus.

 

These KDE monitoring clients include the following:

 

kdf:- A graphical interface to your system’s file system table that displays free disk

space and enables you to mount and unmount file systems with a pointing device.

 

ksysguard:- Another panel applet that provides CPU load and memory use

information in animated graphs.

 

 

 

 

 

 

 

 

 

 

UNIT-IV Backing Up

 

# Choosing a Backup Strategy

 

Your first step in formulating and learning to use an effective backup strategy is to

choose the strategy that is right for you.

 

Why Data Loss Occurs:-

Files disappear for any number of reasons: They can be lost because the hardware

fails and causes data loss; your attention might wander and you accidentally delete

or overwrite a file. Some data loss occurs as a result of natural disasters such as a

tornado, flood or earthquake could strike, the water pipes could burst, or the building

could catch on fire.

All these accidents and disasters offer important reasons for having a good backup

Strategy.

 

On a home system, most files never change, a few change daily, and some change

weekly. A good strategy for home use is to back up (to any kind of removable media)

critical data frequently and back up configuration and other files weekly.

 

At the enterprise level on a larger system with multiple users, a different approach is

called for. Some critical data is changing constantly, and it could be expensive to recreate;

 

Whatever backup scheme you choose, be sure to incorporate in it these three

principles:-

 

1. Have a plan:- Design a plan that is right for your needs and have equipment

appropriate to the task. This involves assessing all the factors that affect the data

you are backing up.

 

2. Follow the plan:- Faithfully complete each part of your backup strategy, and then

verify the data stored in the backups. Backups with corrupt data are of no use to

anyone. Even backup operations can go wrong.

 

3. Practice your skills—Practice restoring data from your backup systems from

time to time, so when disaster strikes, you are ready (and able) to benefit from the

strength of your backup plan Keep in mind that it is entirely possible that the flaws in

your backup plan will become apparent only when you try restoring!

 

Evaluating Backup Strategies

Now that you are convinced you need backups, you need a strategy. It is difficult to

be specific about an ideal strategy because each user or administrator’s strategy will

be highly individualized, but here are a few general examples:

 

1. Home user: - The home user should back up any configuration files that have

been altered, keep an archive of any files that have been downloaded, and keep an archive of any data files created while using any applications. Unless the home user

has a special project in which constant backups are useful, a weekly backup is

adequate. The home user is likely to use a DVD-RW drive or other removable media

for backups.

 

2. Small office: - Many small offices tend to use the same strategy as home users,

but are more likely to back up critical data daily and use manually changed tape

drives. If they have a tape drive with adequate storage, they will likely have a full

system backup as well because restoring from the tape is quicker than reinstalling

from the CDs. They also might be using CD-RW or DVD writers for backups.

Although they will use scripts to automate backups, most of it is probably done by

hand.

 

3. Small enterprise: - Here is where backups begin to require higher-end equipment

such as autoloading tape drives with fully automated backups. Commercial backup

software usually makes an introduction at this level, but a skillful system

administrator on a budget can use one of the basic applications. Backups are highly

structured and supervised by a dedicated system administrator.

 

4. Large enterprise:-These are the most likely settings for the use of expensive,

proprietary, highly automated backup solutions. At this level, data means money, lost

data means lost money, and delays in restoring data means money lost as well.

These system administrators know that backups are necessary insurance and plan

accordingly.

Does all this mean that enterprise-level backups are better than those done by a

home user? Not at all.

 

The following sections examine a few of the many strategies in use today. Many

strategies are based on these sample schemes.

 

Simple Strategy

If you need to back up just a few configuration files and some small data files, copy

them to a USB stick, engage the write-protect tab, and keep it someplace safe. If you

need just a bit more backup storage capacity, you can copy the important files to a

Zip disk.

 

Full Backup on a Periodic Basis

This backup strategy involves a backup of the complete file system on a weekly,

biweekly, or other periodic basis. The frequency of the backup depends on the

amount of data being backed up, the frequency of changes to the data, and the cost

of losing those changes.

 

Full Backups with Incremental Backups

This scheme involves performing a full backup of the entire system once a week,

along with a daily incremental backup of only those files that have changed in the

previous day, and it begins to resemble what a sysadmin of a medium to large

system would traditionally use. This backup scheme can be advanced in two ways.

In one way, each incremental backup can be made with reference to the original full

backup. In other words, a level 0 backup is followed by a series of level 1 backups.

The benefit of this backup scheme is that a restoration requires only two tapes (the

full backup and the most recent incremental backup).

 

Alternatively, each incremental backup could reference the previous incremental

backup. This would be a level 0 backup followed by a level 1, followed by a level 2,

and so on. Incremental backups are quicker (less data each time), but require every

tape to restore a full system. Again, it is a classic trade-off decision.

 

Mirroring Data or RAID Arrays

Given adequate (and often expensive) hardware resources, you can always mirror

the data somewhere else, essentially maintaining a real-time copy of your data on

hand. This is often a cheap, workable solution if no large amounts of data are

involved. The use of RAID arrays (in some of their incarnations—refer to Chapter 35,

“Managing the File System,” for more information on RAID) provides for a recovery if

a disk fails.

 

# Choosing Backup Hardware and Media

Any device that can store data can be used to back it up. Many people use what

hardware they already have for their backup operations. Most consumer-grade

workstations have a CD-RW drive,

You learn about some of the most common backup hardware available and how to

evaluate its appropriateness for your backup needs.

 

Removable Storage Media

Choosing the right media for you isn’t as easy as it used to be back when floppy

drives were the only choice. Today, most machines have CD-ROM drives that can

read, but not write, CDs, which rules them out for backup purposes. Instead, USB

hard drives and solid-state “pen” drives have taken over the niche previously held by

floppy drives. A 500GB USB hard drive costs about $150. The biggest benefits of

USB drives are data transfer speed and portability.

 

FireWire Drives

FireWire (IEEE-1394) hard drives are similar to USB drives; they just use a different

interface to your computer. Many digital cameras and portable MP3 players use

FireWire. Kernel support is available if you have this hardware. The cost of FireWire

devices is now essentially.

 

CD-RW and DVD+RW/-RW Drives

Compared to floppy drives and some removable drives, CD-RW drives and their

cousins, DVD+RW/-RW drives, can store large amounts of data and are useful for a

home or small business. Although very expensive in the past, CD writers and media

are at commodity prices today, but automated CD changing machines, necessary for

automatically backing up large amounts of data, are still quite costly. A benefit of CD

and DVD storage over tape devices is that the archived uncompressed file system

can be mounted and its files accessed randomly just like a hard drive, making the

recovery of individual files easier. Each CD-RW disk can hold 650MB–700MB of

data.

DVD+RW/-RW is similar to CD-RW, but it is more expensive and can store up to

8GB of uncompressed data per disk.

 

 

Network Storage

For network backup storage, remote arrays of hard drives provide one solution to

data storage. With the declining cost of mass storage devices and the increasing

need for larger storage space, network storage (NAS, or Network Attached Storage)

is available and supported in Linux. These are cabinets full of hard drives and their

associated controlling circuitry, as well as special software to manage all of it. These

NAS systems are connected to the network and act as a huge (and expensive) mass

storage device.

More modest and simple network storage can be done on a remote desktop-style

machine that has adequate storage space, but then that machine has to deal with all

the problems of backing up, preserving, and restoring its own data.

 

Tape Drive Backup

Tape drives have been used in the computer industry from the beginning. Tape drive

storage has been so prevalent in the industry that the tar command is derived from

the words Tape ARchive. Modern tape drives use tape cartridges that can hold

70GB of data (or more in compressed format).

 

Capacities and durability of tapes vary from type to type and range from a few

gigabytes to hundreds of gigabytes with commensurate increases in cost for the

equipment and media. Auto loading tape-drive systems can accommodate archives

that exceed the capacity of the file systems.

 

Tape equipment is well supported in Linux and, when properly maintained, is

extremely reliable. The tapes themselves are inexpensive, given their storage

capacity and their opportunity for reuse. Be aware, however, that tapes do

deteriorate over time and, being mechanical, tape drives can and will fail.

 

# Using Backup Software

Linux offers many backup tools. Along with command-line

tools such as tar and dd, Fedora also provides a graphical archiving tool, File Roller,

that can create and extract files from archives. Finally, Fedora provides support for

the Amanda backup application—a sophisticated backup application that works well

over network connections and can be configured to automatically back up all the

computers on your network. Amanda works with drives as well as tapes.

 

tar: The Most Basic Backup Tool

The tar tool, the bewhiskered old man of archiving utilities, is installed by default. It is

an excellent tool for saving entire directories full of files. For example, here is the

command used to back up the /etc directory:

 

# tar cvf etc.tar /etc

 

Here, the options use tar to create an archive, are verbose in the message output,

and use the filename etc.tar as the archive name for the contents of the directory

/etc. Alternatively, if the output of tar is sent to the standard output and redirected to

a file, the command appears as follows:

 

# tar cv /etc > etc.tar

 

The result is the same.

All files in the /etc directory will be saved to a file named etc.tar. With an impressive

array of options (see the man page), tar is quite flexible and powerful

 

Creating Full and Incremental Backups with tar

If you want to create a full backup,

 

# tar cjvf fullbackup.tar.bz2 /

 

creates a bzip2-compressed tarball (the j option) of the entire system.

To perform an incremental backup, you must locate all the files that have been

changed since the last backup. For simplicity, assume that you do incremental

backups on a daily basis. To locate the files, use the find command:

 

# find / -newer name_of_last_backup_file ! -a -type f –print

 

When run alone, find generates a list of files systemwide and prints it to the screen.

The ! -a -type eliminates everything but regular files from the list; otherwise, the

entire directory would be sent to tar even if the contents were not all changed.

Pipe the output of the find command to tar as follows:

 

# find / -newer name_of_last_backup_file ! -type d -print |\

tar czT - backup_file_name_or_device_name

 

Here, the T - option gets the filenames from a buffer

 

The tar command can back up to a raw device (one with no file system) as well as a

formatted partition. For example,

 

# tar cvzf /dev/hdd /boot /etc /home

 

backs up those directories to device /dev/hdd (not /dev/hda1, but to the unformatted

device itself).

The tar command can also back up over multiple floppy disks:

 

# tar czvMf /dev/fd0 /home.

 

Restoring Files from an Archive with tar

The xp option in tar restores the files from a backup and preserves the file attributes

as well, and tar creates any subdirectories it needs. Be careful when using this

option because the backups might have been created with either relative or absolute

paths. You should use the tvf option with tar to list the files in the archive before

extracting them so that you know where they will be placed.

For example, to restore a tar archive compressed with bzip2,

 

# tar xjvf fedoratest.tar.bz2

 

The GNOME File Roller

The GNOME desktop file archiving graphical application File Roller (file-roller) views,

extracts, and creates archive files using tar, gzip, bzip, compress, zip, rar, lha, and

several other compression formats. Note that File Roller is only a front end to the command-line utilities that actually provide these compression formats; if they are

not installed, File Roller cannot use that format.

 

File Roller is well integrated with the GNOME desktop environment to provide

convenient drag-and-drop functionality with the Nautilus file manager. To create a

new archive, select Archive, New to open the New Archive dialog box and navigate

to the directory where you want the archive to be kept. Type your archive’s name in

the Selection: /root text box at the bottom of the New Archive dialog box. Use the

Archive type drop-down menu to select a compression method.

 

Using the Amanda Backup Application

Provided with Fedora, Amanda is a powerful network backup application created by

the University of Maryland at College Park. Amanda is a robust backup and restore

application best suited to unattended backups with an autoloading tape drive of

adequate capacity. It benefits from good user support and documentation.

Amanda’s features include compression and encryption. It is intended for use with

highcapacity tape drives, optical, CD-R, and CD-RW devices.

 

There is no GUI interface for Amanda. Configuration is done in the time-honored

Unix tradition of editing text configuration files located in /etc/amanda. The default

installation in Fedora includes a sample cron file because it is expected that you will

be using cron to run Amanda regularly.

 

# Copying Files:-

when you have only a few files that you need to protect from loss or corruption, it

might make better sense to simply copy the individual files to another storage

medium rather than to create an archive of them. You can use the tar, cp, rsync, or

even the cpio commands to do this.

 

Copying Files Using tar

 

One choice for copying files into another location is to use the tar command where

you would create a tar file that would be piped to tar to be uncompressed in the new

location.

 

# tar cvf - files | (cd target_directory ; tar xpf -)

 

 

where files are the filenames you want to include; use * to include the entire current

directory.

 

Here is how the command shown works: You have already changed to the source

directory and executed tar with the cvf - arguments that tell tar to

· c Create an archive.

· v Be Verbose; lists the files processed so we can see that it is working.

· f Use the filename of the archive will be what follows. (In this case, it is -.)

· - Use a buffer; a place to hold data temporarily.

 

compress the contents of a designated directory, and then decompress

the compressed and encrypted archive stream into a designated directory on a

remote host:

 

 

$ tar cvzf - data_folder | ssh remote_host `( cd ~/mybackup_dir; tar xvzf - )’

 

The tar command is used to create, list, and compress the files in the directory

named data_folder. The output is piped through the ssh (secure shell) command and

sent to the remote computer named remote_host. On the remote computer, the

stream is then extracted and saved in the directory named /mybackup_dir.

 

Copying Files Using cp:

 

To copy files, we could use the cp command. The general format of the command

when used for simple copying is

 

$ cp -a source_directory target_directory

 

The -a argument is the same as giving -dpR, which would be

-d Dereferences symbolic links (never follows symbolic links) and copies the files

to which they point, instead of copying the links.

-p—Preserves all file attributes if possible. (File ownership might interfere.)

-R—Copies directories recursively.

 

You can also use the cp command to quickly replicate directories and retain

permissions by using the -avR command-line options. Using these options preserves

file and directory permissions, gives verbose output, and recursively copies and recreates

subdirectories.

 

You can also create a log of the backup during the backup by redirecting the

standard output like this:

 

# cp -avR directory_to_backup destination_vol_or_dir 1>/root/backup_log.txt

or

# cp -avR fedora /test2 1>/root/backup_log.txt

 

This example makes an exact copy of the directory named /fedora on the volume

named /test2, and saves a backup report named backup_log.txt under /root.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

UNIT-V Networking and TC/IP

 

#Using Network Configuration Tools

If you add or replace networking hardware after your initial installation, you must configure the new

hardware. You can use either the command line or the graphical configuration tools to do so. To

configure a network client host using the command line, you can use a combination of commands or

edit specific files under the /etc/sysconfig directory. To configure the hardware through a graphical

interface, you can use system-config-network or the console-based netconfig command.

 

Using Graphical Configuration Tools:-

The graphical configuration tool is your best method for configuring new hardware in Fedora.

Like most graphical tools, system-config-network enables you to fill in the blanks; press the proper

buttons, and the tool modifies the required files and issues the proper commands. Remember, you

must be root to run system-config-network.

 

There are two ways to start system-config-network: from the command line of an X11 terminal

window with the command system-config-network, using the panel’s Run Application menu item, or

by clicking the System Setting’s Network menu item from a GNOME or KDE desktop panel menu.

 

After it is started, system-config-network might ask whether you would like to create a new device. If

you have installed Fedora on a computer with an existing network card, the appears after you start

system-config-network.

 

Click the DNS tab to configure your system’s DNS settings, hostname, or DNS search path. Click the

Hosts tab, and then click either the New or Edit button (after selecting a host) to create or edit an entry

in your system’s /etc/hosts file—for example, to add the IP addresses, hostnames, and aliases of hosts

on your network.

 

Click the Devices tab, and then either click New or select an existing setting and click Edit to

automatically or manually set up an ethernet device. Shows the Add New Device Type dialog box

with all necessary information in place for a static, or fixed, IP address assignment. Choose how your

card will get its configuration: manually from Dynamic Host Control Protocol (see the next section)

or from Bootp. Just fill in the blanks as needed.

 

When you finish configuring your NIC or editing an IP address or assignment scheme for a NIC, save

your changes, using the File menu’s Save menu item. Note that you can also use the Profile menu to

create different network configurations and IP address assignments for your installed NICs.

 

Command-Line Network Interface Configuration:-

You can configure a network interface from the command line, using the basic Linux networking

utilities. You configure your network client hosts with the command line by using commands to

change your current settings or by editing a number of system files. Two commands, ifconfig and

route, are used for network configuration. The netstat command displays information about the

network connections.

 

 

 

/sbin/ifconfig

 

ifconfig is used to configure your network interface. You can use it to . Activate or deactivate your

NIC or change your NIC’s mode

 

1. Change your machine’s IP address, netmask, or broadcast address

2. Create an IP alias to allow more than one IP address on your NIC

3. Set a destination address for a point-to-point connection

 

 

You can change as many or as few of these options as you’d like with a single command.

The basic structure for the command is as follows:

 

/sbin/ifconfig [network device] options

 

The ifconfig man page shows other options that enable your machine to interface with a number of

network types such as AppleTalk, Novell, IPv6, and others. Again, read the man page for details on

these network types.

 

#Advanced Wireless Networking

Linux has had support for wireless networking since the first standards were developed in the early

1990s.

The Linux kernel that ships with Fedora provides extensive support for wireless networking.

Related wireless tools for configuring, managing, or displaying information about a wireless

connection include

 

iwconfig—Sets the network name, encryption, transmission rate, and other features of a wireless

network interface

iwlist—Displays information about a wireless interface, such as rate, power level, or frequency

used

iwpriv—Uses i to set optional features, such as roaming, of a wireless network interface

iwspy—Shows wireless statistics of a number of nodes

 

Support varies for wireless devices—most likely in the form of a PCMCIA adapter although some

USB wireless devices now work with Linux. In general, Linux wireless device software (usually in

the form of a kernel module) supports the creation of an Ethernet device that can be managed by

traditional interface tools such as ifconfig with wireless features of the device managed by the various

wireless software tools.

 

TCP/IP Addressing

To understand networking with Linux, you need to know the basics of TCP/IP addressing. Internet IP

addresses are assigned (for the United States and some other hosts) by the American Registry for

Internet Numbers, available at http://www.arin.net/. The agency assigns Internet service providers

(ISPs) one or more blocks of IP addresses, which the ISPs can then assign to their subscribers.

You will quickly recognize the current form of TCP/IP addressing, known as IPv4 (IP version 4).

 

The first octet usually determines what class the network belongs to. There are three classes of

networks. The classes are:

 

1. Class A—Consists of networks with the first octet ranging from 1 to 126. There are only 126 Class

A networks—each composed of up to 16,777,214 hosts.

2. Class B—Consists of networks defined by the first two octets, with the first ranging

from 128 to 191.

3. Class C—Consists of a network defined by the first three octets, with the first ranging

from 192 to 223.

 

#Dynamic Host Configuration Protocol

 

Dynamic Host Configuration Protocol (DHCP) is a network management protocol used to dynamically

assign an IP address to nay device, or node, on a network so they can communicate using IP

(Internet Protocol). DHCP automates and centrally manages these configurations. There is no need

to manually assign IP addresses to new devices. Therefore, there is no requirement for any user

configuration to connect to a DHCP based network.

 

 

DHCP can be implemented on local networks as well as large enterprise networks. DHCP is the

default protocol used by the most routers and networking equipment.

 

DHCP does the following:

DHCP manages the provision of all the nodes or devices added or dropped from the

network.

DHCP maintains the unique IP address of the host using a DHCP server.

It sends a request to the DHCP server whenever a client/node/device, which is

configured to work with DHCP, connects to a network. The server acknowledges by

providing an IP address to the client/node/device.

 

DHCP is also used to configure the proper subnet mask, default gateway and DNS server information

on the node or device.

 

 

How DHCP works

 

DHCP runs at the application layer of the TCP/IP protocol stack to dynamically assign IP

addresses to DHCP clients/nodes and to allocate TCP/IP configuration information to the

DHCP clients. Information includes subnet mask information, default gateway, IP addresses

and domain name system addresses.

 

DHCP is based on client-server protocol in which servers manage a pool of unique IP

addresses, as well as information about client configuration parameters, and assign addresses

out of those address pools.

 

The DHCP works process as follows:

First of all, a client (network device) must be connected to the internet.

DHCP clients request an IP address. Typically, client broadcasts a query for this

information.

DHCP server responds to the client request by providing IP server address and other

configuration information. This configuration information also includes time period,

called a lease, for which the allocation is valid.

When refreshing an assignment, a DHCP clients request the same parameters, but the

DHCP server may assign a new IP address. This is based on the policies set by the

administrator.

 

 

Benefits of DHCP

There are following benefits of DHCP:

 

Centralized administration of IP configuration: DHCP IP configuration information can

be stored in a single location and enables that administrator to centrally manage all IP address

configuration information.

 

Dynamic host configuration: DHCP automates the host configuration process and

eliminates the need to manually configure individual host. When TCP/IP (Transmission

control protocol/Internet protocol) is first deployed or when IP infrastructure changes are

required.

 

Seamless IP host configuration: The use of DHCP ensures that DHCP clients get accurate

and timely IP configuration IP configuration parameter such as IP address, subnet mask,

default gateway, IP address of DND server and so on without user intervention.

 

Flexibility and scalability: Using DHCP gives the administrator increased flexibility,

allowing the administrator to move easily change IP configuration when the infrastructure

changes.

 

#Setting Up a Telnet Server

the Telnet server installation packages

under Legacy Network Server in the Add or Remove Packages dialog box. You need to

select it from the Details selection because it is not one of the default selections for the

package group. After it’s installed, select System Settings, Server Settings, Services and

enable Telnet for runlevel 5. Note your IP address while you are here (switch to root and

run ifconfig).

With that done, you can now fire up your other Linux box and type telnet <your IP>.

If you are unsure of your IP address, switch to root and use the ifconfig command. You

are prompted to enter your username and password. The whole conversation should look

like this:

[paul@susannah ~]$ telnet 10.0.0.1

Trying 10.0.0.1…

Connected to 10.0.0.1 (10.0.0.1)

Escape character is ‘^]’.

Welcome to Caitlin

Running Fedora Core

* All access is logged *

login: paul

Password:

Last login: Sat Jul 9 12:05:41 from 10.0.0.5

[paul@caitlin ~]$

 

#Setting Up an SSH Server

The OpenSSH server is set up to be automatically installed and run in Fedora, which means it should

already be working on your system. However, if you have disabled it, you can re-enable it by

selecting System Settings, Server Settings, Services and selecting the sshd box. As you might have

gathered, sshd is the name for the SSH server daemon.

 

Two different versions of SSH exist, called SSH1 and SSH2. The latter is newer, is more

secure, comes with more features, and is the default in Fedora Core Linux.

 

To do this, edit the /etc/ssh/sshd_config file and look for this line:

 

#Protocol 2,1

 

Edit this line so that it becomes:

 

Protocol 2

 

This removes the comment sign (#) and tells sshd that you want it to only allow SSH2

connections. Save the file and exit your editor. The next step is to tell sshd to reread its

configuration file, by executing this command:

kill -HUP `cat /var/run/sshd.pid`

You can test this change by trying to connect to your SSH server in SSH1 mode. From the

same machine, type this:

ssh -1 localhost

The -1 switch forces SSH1 mode.

 

  

PRINTING WITH FEDORA

 

Installing Apache Server:-

 

Open the Terminal (Command Prompt) window on your Linux machine. You can use

the Terminal window to easily download and install the Apache server on your computer.

Depending on your Linux version:

 

Steps1:-

Click the icon on the top-left to open the Dash, type "Terminal," and hit ⏎ Return or ↵

Enter.

Press the Ctrl+Alt+T keyboard shortcut.

Click the Applications tab on the menu bar, select Accessories, and click Terminal.

 

Step2:-

            Type sudo apt-get install apache2 in Terminal. This command will download

and install the Apache server on your Linux machine.

This command will work in Ubuntu and other Debian Linux versions.

For Fedora / RHEL / Cent OS and Red Hat Enterprise Linux, type yum

install httpd

 

Step3:-

            Press ↵ Enter or ⏎ Return on your keyboard. This will run the command, and prompt

you to enter your user/root password.

Step4:-

Enter your user/root password. This will confirm your action, and start downloading

Apache on your computer.

Press ↵ Enter or ⏎ Return to confirm your password.:-

           

Step5:-

            Press Y to continue. When you're prompted to install the required extra packages, type

"Y" and press ↵ Enter or ⏎ Return to proceed.

This will install all the required packages, and start your Apache server on your

computer.

You will see a message saying "Starting web server apache2" in Terminal when your

installation is finished.

     

Step6:-

            Open your internet browser. You can use any internet browser to check if your

Apache server is successfully installed.

 

Step7:-

            Type localhost in your browser's address bar. Your Apache server should

automatically start running on your localhost when it's finished installing.

 

Step8:-

            *Press ↵ Enter or ⏎ Return on your keyboard. The localhost page should open up to

the Apache2 Default Page.

*If you see the Apache2 Default Page, your Apache server is up and running on this

computer.

If your Apache server isn't running, you'll see a message saying "Unable to connect."

 

 

Starting and Stopping Apache:-

SystemD is the service manager for newer Red-Hat based distributions (RHEL and CentOS

7 and later versions). Similarly, for Red Hat distributions, Apache service is referred to as

httpd.

 

To start the Apache webserver service, we use the command:

 

sudo systemctl start httpd

 

To stop the Apache webserver service, we use the command:

 

sudo systemctl stop httpd

 

Whenever we make any changes to Apache’s web server configuration, we need to restart the

Apache service. To restart the service, we use the command:

 

sudo systemctl restart httpd

 

To start the Apache webserver service in older versions, we use the command:

 

sudo service httpd start

 

To stop the Apache webserver service in older versions, we use the command:

 

sudo service httpd stop

 

To restart the Apache service in older versions, we use the command:

 

sudo service httpd restart

 

 

 

Network File System(NFS):-

 

Network File System(NFS) is a file system implemented by Sun Microsystems, Inc. It is a

client/server system that lets the users access files across a network and work on them as if

they are present in a local file directory.

 

For example, if we are using a computer connected to a second computer via NFS, we can

access the files of the second computer as if they are located in a directory on the first

computer. This is done by exporting(the process through which an NFS server gives remote

clients access to its files) and mounting(the process by which the client maps NFS shared file

system).

 

For NFS, we should have the client and server machine configuration.

 

Steps to configure the NFS server machine:-

Become a root user, with the command:

su –

 

To verify if the package nfs is installed in the system, with the command:

rpm -qa | grep nfs

 

If not installed, run the command to install:

yum install nfs-utils libnfsidmap

 

Enable and start the nfs services by running commands one by one:

systemctl enable rpcbind

systemctl enable nfs-server

systemctl start rpcbind

systemctl start nfs-server

systemctl start rpc-statd

systemctl start nfs-idmapd

 

To check the status of a service, for example: rpc-statd, run the command:

systemctl status rpc-statd

 

Create an nfs shared directory and assign permissions with the following steps:

Create a directory mypretzels at the / location with the commands:

 

cd /

mkdir mypretzels

 

Assign permissions to the directory with the command:

 

chmod a+rwx mypretzels/

 

Create files a, b, c, and kramer inside the mypretzels directory with the commands:

cd mypretzels/

touch a b c

touch Kramer

 

Add some content to the kramer file, with the command:

echo "These pretzels are making me thirsty" > Kramer

 

To get the contents of the mypretzels directory, run the command:

ls -ltr

 

Edit the /etc/exports file with the command:

vi /etc/exports

 

In the insert mode, add the following lines:

/mypretzels *(rw,sync,no_root_squash)

 

Save and quit.

:wq!

 

Export the nfs filesystem with the command:

exportfs -rv

 

Check the IP address of the server machine, with the command:

Ifconfig

 

The IP address of the server machine is 192.168.1.18.

 

Steps to configure NFS client machine:-

 

Become a root user, with the command:

su –

 

Check the IP address, with the command:

ip addr

 

The IP address of the client machine is 192.168.1.11

 

Install the nfs package with the command:

yum install nfs-utils

 

Install the rpcbind package with the command:

yum install rpcbind -y

 

Once installed, enable and start the rpcbind package with the command:

systemctl start rpcbind

 

Check the status of the rpcbind package with the command:

systemctl status rpcbind

 

Ensure that the firewalld or iptable are stopped, with the command:

ps –ef | egrep “firewall|iptable”

 

Show mount from the nfs server with the command:

showmount -e 192.168.1.18

192.168.1.18 is the IP address of the server machine.

 

Create a mount point with the command:

mkdir /mnt/kramer

 

Mount the nfs filesystem with the command:

mount 192.168.1.18:/mypretzels /mnt/Kramer

 

Verify the mounting system with the command:

df –h

 

 

Putting Samba to Work:-

1.Configuring Samba with System config-samba:-

 

Samba (SMB) is an open source and free software suite that runs on Linux/UNIX based

system but it also communicate with Windows client like a native application. It is a file

sharing server. It is used to share files between Windows and Linux/UNIX systems. Samba is

able to provide this service by employing the common Internet File System (CIFS). The

heart of CIFS is the Server Message Block (SMB).

 

you can configure SAMBA server in Linux systems. Follow the below steps.

 

Step #1 . First you will need to create a directory where you want to keep data and share with

other remote system such as Solaris,Windows, UNIX etc.

 

# mkdir /data

 

Step #2. Now you will need to install Samba server on system.

 

On RHEL/Fedora/CentOS

 

# yum install samba

 

On Ubuntu/Debian

 

$sudo apt-get install samba

 

Step #3. After installing samba server, configure it using it’s main configuration file

“/etc/samba/smb.conf“.

 

# vim /etc/samba/smb.conf

 

workgroup = windows-group.

 

server string = Linux-Share

 

[sharedfolder]

comment = secured shared folder

path = /srv/samba/data

Valid users = sagar faeem

guest ok = no

writable = yes

privatable = no

browsable = yes

 

Save and exit

 

Where:

 

Workgroup : Where this server belongs. When windows user try to access any

network resource they first try to access my network place and then search for

workgroup then to server.

 

server string : Name of this samba server search, Here that name is Linux-Share.

 

[sharedfolder] : Share name, When any users access samba server through network

this will be visible as folder shared.

 

comment : Use for any comment, which help to know what is this share for.

 

path : Location of shared folder, this is used to specific which folder you want to

share.

 

valid users : Specifies which user is having access on this folder.

 

writable : Privide the access control to user whether users are able to write or not. In

this example they can read and write.

 

privatable : It indecate whether this folder is private or not.

 

browsable : It is used to specify whether the folder content is browsable or not.

 

Step #4. Now create password for the users. So that users can access this samba share

remotely.

 

#smbpasswd -a sagar

#smbpasswd -a faeem

 

Set the password for above users, password is stored in ” /etc/samba/smbpasswd ” file.

 

Step #5. Execute the below command for syntax check for smb.conf file.

 

# testparm

 

Step #6. Now restart samba service.

 

# service smb restart

 

Step #7. Keep on samba service on during booting time, samba service will start if server

restarted.

 

#chkconfig smb on

 

 

 

2.Configuring Samba with SWAT:-

 

SWAT should be installed to run via the network super-daemon. Depending on which system

your UNIX/Linux system has, you will have either an inetd - or xinetd -based system.

 

The nature and location of the network super-daemon varies with the operating system

implementation. The control file (or files) can be located in the file /etc/inetd.conf or in

the directory /etc/[x]inet[d].d or in a similar location.

 

The control entry for the older style file might be:

 

# swat is the Samba Web Administration Tool

swat stream tcp nowait.400 root /usr/sbin/swat swat

 

A control file for the newer style xinetd could be:

 

# default: off

# description: SWAT is the Samba Web Admin Tool. Use swat \

# to configure your Samba server. To use SWAT, \

# connect to port 901 with your favorite web browser.

service swat

{

port = 901

socket_type = stream

wait = no

only_from = localhost

user = root

server = /usr/sbin/swat

log_on_failure += USERID

disable = no

}

 

In the above, the default setting for disable is yes. This means that SWAT is disabled. To

enable use of SWAT, set this parameter to no as shown.

 

Both of the previous examples assume that the swat binary has been located in the

/usr/sbin directory. In addition to the above, SWAT will use a directory access point from

which it will load its Help files as well as other control information. The default location for

this on most Linux systems is in the directory /usr/share/samba/swat. The default location

using Samba defaults will be /usr/local/samba/swat.

 

Access to SWAT will prompt for a logon. If you log onto SWAT as any non-root user, the

only permission allowed is to view certain aspects of configuration as well as access to the

password change facility. The buttons that will be exposed to the non-root user are HOME,

STATUS, VIEW, and PASSWORD. The only page that allows change capability in this case

is PASSWORD.

 

As long as you log onto SWAT as the user root , you should obtain full change and commit

ability. The buttons that will be exposed include HOME, GLOBALS, SHARES, PRINTERS,

WIZARD, STATUS, VIEW, and PASSWORD.

 

 

 

 

 

Configuring and Managing Print Services:-

 

Your task as a system administrator (or root operator of your workstation) is to properly define local or

remote printers and to ensure that printing services are enabled and running properly. Fortunately,

Fedora includes a graphical print service configuration tool that makes this job easy.

 

You can configure printing services using either the command line system-config-printer-tui program

or the

system-config-printer-gui graphical interface. Most of the detailed information in this chapter refers to

the use of the GUI.

 

GUI-Based Printer Configuration Quickstart:-

 

Configuring a printer for Fedora is easy but you must use root permission to do it. Make sure that the

cupsd daemon is installed and running. If you elect to use printing support when you install Fedora,

the daemon and related software will be installed. If you’re not sure whether cupsd is running, you can

quickly drop to a terminal and use the service command with the name of the service and the status

keyword like so:

 

# service cups status

You will see either

cupsd is stopped

or, if cupsd is running, an acknowledgement, along with its process ID, such as

cupsd (pid 2378) is running...

If cupsd is installed but not running, start the daemon like so:

# /etc/rc.d/init.d/cups start

You can also use the service command to start the daemon, like so:

# service cups start

 

If you are using the desktop, select System, Administration, Printing. You will be asked to enter the

root password. If not, you are using X as root, which is a bad idea. Log out, and then log back in as a

regular user! After you enter the root password, the printer configuration dialog appears.

 

You then simply follow the prompts to define your printer and add local or remote printing services.

You should print a test page before saving your changes. Use the printer configuration client or the

File menu’s Print menu item from a GNOME or KDE client.

 

Managing Printing Services:-

 

After defining a printer, you can use the command line to view and control your print jobs, or if root, all

print jobs and printers on your system..

 

Most Linux systems use PostScript as the default document format for printing. Fedora uses the gs

command along with CUPS to manage local and remote print jobs and the type of data transferred

during a print job. The gs command is used to translate the document stream into a format accepted

by the destination printer (which most likely uses HPCL).

 

You can use the Ghostscript interpreter gs to display its built-in printer devices by using the gs

interpreter with its --help command-line option like this:

# gs –help

 

The gs command outputs many lines of help text on command-line usage and then lists built-in printer

and graphics devices. Another way to get this information is to start gs and then use the devicenames

== command like this:

 

# gs

 

 

 

 

Creating and Configuring Local Printers:-

 

Creating a local printer for your Fedora system can be accomplished in six easy steps. You must have

root permission to use the system-config-printer client. The cupsd daemon should also be running

before you begin.

 

To launch system-config-printer, go to System, Administration and choose the Printing

menu option or use the command line of an X terminal window like this:

 

# system-config-printer &

 

Creating the Print Queue:-

The Fedora system-config-printer tool walks you through a process to create a new print queue, which

effectively defines a new printer on your system. To begin configuration of a local (attached) printer,

click the New Printer toolbar button in system-configprinter’s main window. An Add a New Printer

configuration dialog appears, as shown in Figure 8.1.

 

The Printer Name dialog appears. Type a desired name for the new printer (such as lp), enter a short

description and optional location information and then click the Forward button. The Connection Type

dialog appears, as shown in Figure 8.2. Select the connection type that is appropriate for you. You

can select a number of different connection types, depending on your specific requirements. Normally

you will use the LPT#1 option if your printer is connected by a standard Parallel (or what used to be

called Centronics) cable. Alternatively, if you are connecting to a printer that has a JetDirect port (most HP networkcapable printers fit in this category) then select the appropriate option and enter the network address

for the printer. 

  

 

 

FIGURE 8.1 Click the New Printer toolbar button to start the configuration of a new printer

for your system.. 

8

 

FIGURE 8.2 Select the appropriate connection method for your printer and enter the relevant details.

 

Next up you need to select the make/manufacturer of the printer that you are setting up, shown in

Figure 8.3 .

 

 

FIGURE 8.3 Select the make or manufacturer of your printer from this dialog box to help Fedora

narrow down the driver options.

 

Note that you can configure a printer for Fedora even if it is not attached to your computer. After you

select your printer’s manufacturer, a list of printers from that manufacturer (such as HP, as shown in

Figure 8.4) appears. Select your printer from the list, and then click the Forward button.

 

Do not worry if you do not see your printer listed in the selection; it is possible to select a related,

although different, printer model and still be able to print to your printer. For example, many HP

printers can be used by selecting the DeskJet 500 for monochrome or 500C model for color printing.

You can experiment to see which printer selection works best for your printer if its model is not listed.

You might not be able to use all the features of your printer, but you will be able to set up printing

service. Click Next when you have made your choice.

 

 

FIGURE 8.4 Select your printer from the list and click the Forward button to finish the configuration

of a locally connected printer.

 

The final screen summarizes what system-config-printer is about to do. If you are happy with the

details, click the Apply button to commit your changes to the system.

 

 

 

FIGURE 8.5 Double-check your settings before you commit to creating a new printer entry in

/etc/printcap; when the settings are right, click Finish to create the new print queue.

 

 

When the print queue has been created, you are asked whether you would like to print a test page.

Click Yes to save your new printer setup and to print a test page. If you click No, a test page is not

printed, and you have to delete the new printer entry or save or cancel your changes before you quit

system-config-printer.

You can see the new printer defined in the system-config-printer main window as shown in Figure 8.6.

 

 

FIGURE 8.6 New printer entries created in /etc/printcap displayed in system-configprinter’s main

window.

 

Editing Printer Settings:-

You also use the system-config-printer tool to edit the newly defined printers. To edit the printer

settings, highlight the printer’s listing in the printer browser window. You can

then select specific settings related to that printer by using the tabs that appear in the right side of the

dialog box. The Printer Options dialog, part of the printer settings is shown in Figure 8.7.

 

 

 

FIGURE 8.7 Edit a printer’s settings by using tabs in system-config-printer

 

The first tab in this dialog enables you to assign a new name for the printer. In this example, the

printer has the name laserjet. Other tabs in this dialog enable you to change the queue type or queue

options (such as whether to print a banner page or set the image area of a page), to select or update

the driver, or to choose available driver options for the printer (shown in Figure 8.8).

 

 

FIGURE 8.8 A printer’s driver settings can be changed on the Settings tab of system-config-printer’

 

 

When you finish editing your printer definition (or queue), click the OK button. Use the Apply

command in the Action menu to save the definition and automatically restart the cupsd daemon. This

step is extremely important; you have to update the printer settings and restart the cupsd daemon to

force it to reread your new settings. Click Quit from the Action menu when finished.

 

Network and Remote Printing:-

Setting up remote printing service involves configuring a print server and then creating a

remote printer entry on one or more computers on your network. This is a quick method of

enabling printing from one Linux workstation to another Linux computer on a LAN.

 

Enabling Network Printing on a LAN

 

To set up printing from one Linux workstation to another across a LAN, you need root

permission and access to both computers, but the process is simple and easy to perform.

First, log in or ssh to the computer to which the printer is attached. This computer is the

printer server. Use the hostname or ifconfig commands to obtain the hostname or IP address

and write down or note the name of the printer queue.

 

 

This enables incoming print requests with the proper queue name (name of the local printer)

from any remote host to be routed to the printer. After you finish, log out and go to a remote

computer on your LAN without an attached printer.

 

If the computer with an attached printer is using Fedora and you want to set up the system

for print serving, again use the system-config-printer client. You can create a new printer, but

the easiest approach is to publish details of your printer across the network.

 

To enable sharing, start system-config-printer, and then select the Server Settings option in

the left pane. All you need to do is select Share Published Printers Connected to This

System to automatically allow access to all your printers, as shown in Figure 19.9.

 

 

FIGURE 19.9 Sharing enables you to offer a locally attached printer as a remote printer on

your network.

 

By default, all users are allowed access to the printer. You can change this setting by

selecting the Access Control tab and adding users into the list.

 

Finally you need to allow Fedora to publish your selected shared printers across the

network. Click the Server Settings and make sure the Share Published Printers Connected

to This System option is checked.

 

When finished, click the Apply button and then select Quit from the Action menu to exit.

 

To create a printer queue to access a remote Unix print server, use system-config-printer to

create a printer but select the Internet Printing Protocol (IPP) type. Click Forward and enter a

printer name and description; you are then asked to enter the hostname (or IP address) of

the remote computer with a printer, along with the printer name, as shown in Figure 19.10.

 

 

FIGURE 19.10 Enter the hostname or IP address of the remote computer with a printer,

along with the remote printer’s queue name.

 

Click the Forward button after entering this information; then continue to configure the new

entry as if the remote printer were attached locally (use the same print driver setting as the

remote printer). When finished, do not forget to save the changes!

 

You can also test the new remote printer by clicking the Tests menu item and using one of

the test page items, such as the ASCII or PostScript test pages. The ASCII test page prints a

short amount of text to test the spacing and page width; the PostScript test page prints a

page of text with some information about your printer, a set of radial lines one degree apart,

and a color wheel (if you use a color printer).