You might want to go through my previous post on Overview of FTP on Enterprise Linux convering all the basic details which will be used in configuring an FTP in this post.

Ensure that FTP is allowed through the firewall else SELinux is off and iptables are off. Start with installing the FTP package “vsftpd” using YUM. For creating a Yum in Enterprise Linux you may want to go through this post. You need to have root access in to configure an FTP Server.

#yum install vsftpd

Once you install this package the following directory will be created /var/ftp/pub . where you actually have files to be shared on the FTP , although you may give access to your local users to access their home directories as well but this is far to advanced and various constraints of security are needed to be considered before choosing that option. For now let’s configure the pub directory to be accessed via ftp user.

Next you need to configure the ftp configuration file in order to create an FTP Server. The configuration file for FTP is vsftpd.conf and needs to be edited as follows

#vi /etc/vsftpd/vsftpd.conf

You can enable or disable much functionality using this configuration file. For this post we will set FTP so that anonymous user may not be able to login, local user are allowed to login, local user are able to write , make directories and able to upload and download files you may further want to change idle time out settings etc which you may do by changing values in this configuration file.

For this in line 12 set anonymous enable to no

In Line 18 uncomment the write enable=yes

Uncomment line number 27

Uncomment line 31

After this editing save the file and exit.

Now you need to restart the ftp service for the changes to take effect.

#service vsftpd restart

You may login to this ftp server by unix or windows operating system

In Linux simply enter the command like

#ftp <ip-address>

Than supply username and password of the local user, you download and upload files by using get and put command inside the Ftp terminal, when you want to exit use “bye”

Remember users like root are not allowed to login via ftp by default. If you still want to login via root user than you need to perform some additional steps , wait for my next post for this.

In windows operating system, use ftp client software such as filezilla to transfer file via ftp.

Still have some doubt leave it in comment section, we will get back to you.

FTP uses a virtual login to server and is security enabled.

FTP is shipped in Linux with a package named “vsftpd”. You may install the vsftpd package using the yum. you might want to check my earlier post on making a local yum repository or a public yum repository.

The DAEMON i.e (Disk and execution Monitor) for FTP is /usr/sbin. Through Daemon you may start or stop the service.

Some other useful information about FTP is

Type:- system v-managed service (standalone service).

Ports:- ftp(121) and ftpdata(20)

Package:- vsftpd

Daemons:- /usr/sbin/vsftpd .

Document:- /var/ ftp/ pub

Configuration file:-

• /etc/vsftpd/vsftpd.conf      (main configuration file)
• /etc/vsftpd/user_list           (user list not allowed to login through ftp)
• /etc/vsftpd/ftpuser              (Second configuration file with user list)

You would need to deselect the user e.g. root , from both the file listed above in order to login through the FTP.

Once FTP configured you may login to Remote Linux server using FTP client like filezilla.

You may login as “anonymous” user through FTP but it is not recommended. Always maintain a separate FTP user list in order to authenticate through FTP.

It enables applications to access different, multiple, naming and directory services using common API which makes it possible for the different naming and directory services providers to be plugged seamlessly behind this common Api. So Java technology based applications to take advantages of information in a variety of existing naming and directory services such as LDAP, NDS, DNS and NIS as well as enabling applications to coexist with legacy software and systems.

Using JNDI as a tool, new powerful and portable applications can be built that not only take advantage of Java’s object model but are also well-integrated with the environment in which they are deployed.

Tier does not mean a physical machine but rather is a logical grouping of services normally spread across more than one machine. Oracle applications can be installed on a single machine and all the servers can be start from that machine. Although many physical machines may be used in configuration, scalability is derived from the processing capabilities on three separate levels namely; the desktop client tier, the application tier, and the database tier.

Shell scripts are useful for:

• Automating commonly used commands
• Performing system administration and troubleshooting
• Creating simple applications
• Manipulation of text or files.

A shell script is simply a text file containing commands. Scripts are useful for automating processes that you perform repeatedly at the command line. For example suppose every morning when you log in, you perform the following operations:

• Check the system dare.
• Look at the calendar for thr current month.
• Check your email.
• Display the list of logged in users.

Instead of entering the commands to perform steps 1-4 individually, you could create a shell script containing those commands. Every morning you could enter just one command to perform all these steps. In addition the key benefit of using Linux is using the powerful, yet simple commands. These commands may be put together in a script to perform complex operations or automate procedures such as adding batches of users.

Linux users involved with system administration and troubleshooting often work with shell scripts. Many of these are created during the installation of the operating system. Consider the script /etc/profile. This file is the system- wide user login script which runs whenever a user logs into the system. System administrators and troubleshooters will consider operations performed in this script when troubleshooting user login problems.

Programmers often create simple versions of programs using scripts during the initial phases of a programming project. This is called application prototyping. Once they and the program’s users are happy with the main functionality of the program, the programmer will then create the full-featured program in a programming language such as C.

CISC stand for “Complex Instruction Set Computing”. CISC is a CPU design techniques and makes the use of complex instruction architecture for performing the processing and execution of the tasks. The primary goal of the CISC architecture was to reduce the execution of the task in as minimum assembly language programming as possible. In order to achieve this goal the main emphasis was on the computer hardware that can understand and execute a series of the operations. It was capable to execute the several low-level operations (like memory store, load from memory) and is also capable of multi- step operations within the single instructions. So for multiplying task the CISC processor would come prepared with a specific instruction in the form of “MULT”. When the MULT was executed, the instruction will load the two values into the two separate registers, multiplies the operands, and then store the product in the appropriate register. So for multiplying two numbers the instruction used was:

MULT 4:5, 7:8

MULT is known as “complex instruction” which operates directly in memory and doesn’t any loading and storing of the functions.

Examples of the CISC instruction set architectures are System/360, PDP-11, VAX, Motorola68k and x86.

The advantages include such as that compiler has to do very little work to translate the high level instruction statement into assembly and as the length of the code is small so very little RAM memory is required to store the instructions. The main emphasis of this architecture was to put on the complex instructions directly in the hardware.

But due to the design limitations and high level of complexity with the design used in CISC architecture, it saw a set back and the manufacturers move on to use the RISC which reduced the complexity to a very minimum rate, more stress was focused on programming and sequencing the code rather than implementing all of them on the hardware by the use of transistors.

Summing up the CISC architecture:

• The main emphasis was on the hardware rather than software.

• CISC architecture used the ‘multi-clock’ complex instructions.

• Commands like “LOAD” and “STORE” were incorporated in the instructions itself and were allocated from memory-to-memory rather than the registers.

• Although the code size was small but it used high cycles per second.

• Transistors used for storing the complex instructions.

• Great deal of work was on the part of the processor.

Skype is a voip i.e. voice over internet telephony service which also provides you with the features like chat, video-voice chat, screen sharing, and calling telephone numbers at cheap call rates throughout the world almost in all the countries.

The major feature of skype is its online calling service between the PC is absolutely free and moreover has an excellent sound quality. Moreover the call rates are also very cheap.

You can install the skype on Linux as follows.

• Download the skype installation software from here .
• Change your directory to were you have saved the setup files which in our case is at Desktop of the root user.

#cd /root/Desktop

• The downloaded file will be a tar file (skype_static-.tar.bz2) so you can simply install it with the following command.

#tar -xvjf skype_static-.tar.bz2

• This will install the software and a directory will be created at the Desktop (skype_static-…..). You need to change your directory to the newly created once

# cd skype_static-……

• Now you can run the skype by following command.

# ./skype

It will show you the license agreement of the skype. Once you accept the license it will take you to the login screen as shown below

Here you need to enter your skype name and password to start using the skype.

• If you want to share the skype amongst all the user you need to share it under the /usr/share , /usr/bin  or you may provide it on the user’s desktops by moving skype to ~/Desktop.

# cp -rf  /root/Desktop/skype  /usr/share

# cp -rf  /root/Desktop/skype  /usr/bin

A view is a logical table based on table or another view which is used to present the combinations of data present in the database. A view as itself doesn’t contain any data but it is more like a window through which the data from the tables can be viewed or changed. The table on which view is based is known as the base table and view is stored as a select statement in the data dictionary.

Advantages of Creating a View:-

• It restricts the data access to predefined tables and columns so that a database user can see only information relevant for him.

• It makes the complex queries easy.

• Provides the data independence.

• Can be used to present the different views of the same data.

There are majorly two types of views:-

1.    Simple Views

2.    Complex Views

The major difference b/w the two lies in the DML operations.

Syntax for creating a view:-

• Force creates the view regardless of whether the base table exists or not.

• OR REPLACE re-creates the view if already exists.

• NOFORCE creates the view only if the base table exist this is by default.

• WITH CHECK OPTION specifies that only rows accessible to the view can be inserted or updated.

• WITH READ ONLY ensures that no DML operations can be performed on this view.

Example:-

• Creating a view of employees in department 80

• You can add a column alias in the subquery.

RETRIEVING DATA FROM A VIEW:-

• It is same as retrieving a data from a table

You can also refer to USER_VIEWS to see the name and definition of a view.

MODIFYING A VIEW:-

You can modify a view via CREATE OR REPLACE VIEW clause.

RULES FOR PERFORMING DML OPERATIONS ON A VIEW:-

Data may not be added through a view if the view includes:

• Group functions

• A GROUP BY clause.

• The DISTINCT keyword

• The pseudocolumn ROWNUM keyword

• Columns defined by expressions.

• NOT NULL columns in the base tables that are not selected by the view.

REMOVING A VIEW:-

You can remove a view without the loss of data because view is based on underlying tables in the database which is not removed by removing a view

• DROP VIEW view;

Below is an example of a script file by which you can determine whether a file exists or not. This script is used to tell you only whether file exists or not, but not its location as to where it is located. For that you can use FIND OR LOCATE command. We have created a file named existence-of-file.sh you may create a file with some other name. But it is convenient to save the file with ( .sh ) extension so that at later point of time you can recognize that it is a script file. Also in below code whatever is in front of # is a comment.

• # vi existence-of-file.sh  <filename.sh>

#

# Determining whether a file exist or not, filename is supplied as an command line argument

#

if [ $# -ne 1 ]

then

echo “Usage – $0  file-name”

exit 1

fi

if [ -f $1 ]

then

echo “$1 file exist”

else

echo “Sorry, $1 file does not exist”

fi

#

Save and exit from vi ( wq! )

• next you need to make this script file executable which can  be done by following command

# chmod +x existence-of-file.sh

# chmod 755 existence-of-file.sh

• Now everytime you execute this script provide the filename and in the next line it will determine whether a file exist or not.

# ./ existence-of-file.sh <filename>

Mozilla thunderbird is the one of the most famous free open source, cross-platform e-mail and news client developed by the Mozilla foundation.  You can easily receive mail from different mail providers on your desktop and can even store these mails on your local desktop alone. Further you can also remain updated with latest new around the globe or locally by using it. Mozilla thunderbird is just like Microsoft outlook express with only difference is that it supports both IMAP and POP3.  And also unlike outlook express it is open source and can be used equally well on various platforms including Linux. You can simply install thunderbird on Linux by downloading its package from the Mozilla’s site.

Here is a link to Mozilla thunderbird package

http://www.mozillamessaging.com/en-US/thunderbird/

After downloading the package just follow the steps to install and configure an email client

• Navigate to the directory were you have downloaded the package (thunderbird-3.1.6.tar.bz2). In our case it is on the Desktop

# cd /root/Desktop

#ls

Look out for “thunderbird-3.1.6.tar.bz2”

• Next you need to install the package. For this you can use the following command

# tar –xvf thunderbird-3.1.6.tar.bz2    (where x=extract, v=verbose, f=from and next to it is archive file)

• This will extract the archive file and create a folder named “thunderbird”. You need to navigate to that folder

# cd thunderbird

• This folder contains all the files needed for thunderbird. You can run the thunderbird from here by using

# ./thunderbird

• This will open the Thunderbird initial screen for you .

Here you need to enter your name, email address and password.

• Next it will ask you to use IMAP or POP3 protocol. The major difference is that by using IMAP you have your mails on server also which you can access later for some other place also while pop3 downloads the actual message to your local PC. For most of the users default setting will work.

Just make sure IMAP is selected

• Next click on the create account. If you have entered the correct email and password it will download the mails for you.

• If you need to edit/change any information to your account on thunderbird you can do it via going to –àedit tab—àaccount settings. Here it stores the information about all your accounts including SMTP (simple mail transfer protocol) which you need to provide in case you using e-mail other than Gmail.