Fun With Linux

LDAP, Lightweight Directory Access Protocol

2009-11-21T16:04:00.001+05:30

http://funlinuxfun.blogspot.com/

LDAP, Lightweight Directory Access Protocol, a directory service internet protocol runs over Transmission Control Protocol/internet Protocol (TCP/IP) that that email and other programs use to look up information from a server.

Every email program has a personal address book, but how do you look up an address for someone who’s never sent you email? How can an organization keep one centralized up-to-date phone book that everybody has access to?

That question led to development of a standard called DIRECTORY SERVICES which supports the capability to locate certain types of information easily, efficiently, and quickly.

A directory is a set of objects with attributes organized in a logical and hierarchical manner. A simple example is the telephone directory, which consists of a list of names (of either persons or organizations) organized alphabetically, with each name having an address and phone number associated with it.

For example, the entry for Rohit Mehta might have the following attributes:

cn: Rohit Mehta
mail: rohitmehta.linux@gmail.com
telephoneNumber: 9663399899
telephoneNumber: 080-40022300
roomNumber: 353


Lightweight Directory - Directories are kind of like a database but not really. A directory is a specialized
database that is optimized for lookups. Unlike a traditional RDBMS, LDAP is not designed to show
complex relationships between relations. Imagine if 99% of your actions on were going to be simple
"selects", and you wanted anyone, anywhere to be able to do these selects over the Internet. This is
where LDAP excels. Examples of directories are the TVGuide, the phone book, a library card
catalog, and DNS.

"Give me the phone number of John Smith."

"Give me all the tv shows that are on tonight on the Sci-Fi channel."

Access Protocol - LDAP is an outgrowth of the x.500 standard. LDAP is an open standard,
unlike many other proprietary directory solutions. Most of the directory-like solutions that were
out on the market are now very similar to LDAP. Some of these solution providers, Sun and
 Microsoft specifically, have designed JNDI and ADSI APIs so that you can connect with any
 kind of directory service. This is kind of like ODBC or JDBC is to an RDBMS.
 
Cool things you can do with LDAP
 
-Contact Management

-Users and Security

-Image storage

-Document Management

-Store business logic - actual code or SQL statements

The Future Is Here

2009-11-17T10:34:00.005+05:30

http://funlinuxfun.blogspot.com/
http://www.youtube.com/watch?v=GmqJr2ijKIo

What is a zombie process???

2009-11-17T10:25:00.001+05:30

http://funlinuxfun.blogspot.com/
Zombie process is a process observed in Unix/Linux operating system. Zombie process are those process which has finished execution but still have an entry in the process table. This entry for the zombie process is used by the parent to know about the exit status of its child .

After the zombie is removed, its process id and entry in the process table can then be reused but until its entry is in the process table that value cannot be used for other process in case the parent spawns the new process. It will allocate a new pid different from that of zombie process to the new process created.

Zombies can be identified in the output from the ps command in Linux by the presence of a “Z” in the “STAT” column.

To remove zombies from a system, the SIGCHLD signal can be sent to the parent manually, using the kill command. If the parent process still refuses to reap the zombie, the next step would be to remove the parent process. When a process loses its parent, init becomes its new parent. Init periodically executes the wait system call to reap any zombies with init as parent.

How does SSH(Secure Shell) works

2009-11-17T10:23:00.003+05:30

http://funlinuxfun.blogspot.com/
You must have done remote file sharing and remote logins. Have you ever thought that whether your communication over the channel is secure or not. If you are using tools/utilities like ftp , telnet then you are not secure. SSH acronym for Secure Shell enables you to have transfer over the network in the encrypted manner.

This is how SSH works:
When a user attempts for a remote login using SSH ,for the first time it prompts for the generation of keys. SSH uses asymmetric Encryption. Asymmetric encryption also allows for digital certificates.

Two types of key are generated:

Private key : This key is kept only with the user who generated the key and is used for encrypting the messages before sending them over the network.

Public key : This key is distributed to all the users with which you want to encrypt your communication .Remote system uses this key to decrypt the encrypted messsages which is sent by the user to the remote machines.

This is how SSH actually works:

SENDER:

generate public/private key pair : P and S
 publish public key P .guard private key S
encrypt message M with private key S
 send recipient S(M)

RECIPIENT:

decrypt with sender’s public key to recover M=P(S(M))

For making remote login through ssh :
At the hash prompt:

#ssh 192.168.1.1

then type yes for the generation of the keys and then enter the password for the remote system and you are logged into the system

Enjoy the encrypted communication and stay away from network hacks.

Error message : device or resource busy

2009-11-17T10:20:00.001+05:30

http://funlinuxfun.blogspot.com/

You may have encountered the error message:

Cannot open /dev/hda9 : device or resource busy

in linux many times..where /dev/hda9 is one of your partitions of your hard drive /dev/hda..and 9 is the partition number.

This can happen due to one of the following reasons:-

1.The device could be mounted somewhere.To fix this

Check /etc/fstab file.

#cat /etc/fstab

We can see that the last line contains /dev/hda9 mounted on /quota folder.

Comment out this line

Open /etc/fstab file with your favourite editor..we will use vi editor here.

#vi /etc/fstab

Go in insert mode by pressing ‘i’ and comment out the line.

Move out of the editor with [esc] and then :wq

Then,

#umount /dev/hda9

#mount –a

Now check with,

#mount

You will not see /dev/hda9 mounted.

2.Another reason may be that the device you are trying to access (or use) is supposedly busy (in use) or that a resource it needs (such as an IRQ) is supposedly being used by another device and can’t be shared. This message is easy to understand if it only means that the device is busy (in use). But it sometimes means that a needed resource is already in use (busy). What makes it even more confusing is that in some cases neither the device nor the resources that it needs are actually “busy”.

What Is A Gravatar And How To Setup Gravatar Account

2009-11-17T10:17:00.001+05:30

http://funlinuxfun.blogspot.com/
In times one was afraid of giving his/her e-mail address on some blogs , forums ,and sites as he was afraid of spamming.

Tom Werner discovered the solution and what is known as gravatar. So what is a gravatar???

Gravatar short for GLOBALLY RECOGNIZED AVATAR is aservice for providing globally-unique avatars. Gravatar, users can register an account based on their email address, and upload an avatar to be associated with the account.

To eliminate spam, e-mail addresses in gravatar are hashed with the Md5 cryptographic hash function.

Setting up an gravatar account:

It all starts when you sign up for a free account (and yes you do have to give a working email address as confirmation for your account setup is sent to it). Once you account is set up, you can upload your first avatar. Avatars can be uploaded from a hard drive, web address and even a webcam device. Once your avatar is uploaded, you will be asked to crop it (gravatar’s cropping tool is very flexible and easy to use) so it will look nice. After cropping and clicking on the “crop and finish!” button, a “select avatar rating” page will be shown. There you will be required to rate the avatar as one of the following:

rated gravatar is suitable for display on all websites with any audience type.

rated gravatars may contain rude gestures, provocatively dressed individuals, the lesser swear words, or mild violence.

rated gravatars may contain such things as harsh profanity, intense violence, nudity, or hard drug use.

rated gravatars may contain hardcore sexual imagery or extremely disturbing violence.

After selecting the rating the following screen will appear and then click on the link “check this avatar” to get your confirmation and encrypted email-address.

For me it showed my encypted email id like this:

Address: emailid@yahoo.co.in

Hash: 2b3f0a93a608e3eb869554e46b3d71ad

http://www.gravatar.com/avatar/2b3f0a93a608e3eb869554e46b3d71ad?s=80

Why do we use gravatar????

Gravatar acts as a personal representations (or pictures) which help to distinguish one user from the next. If every user had the same default image, chaos could result and everyone would blend into a one color oceaning softwares.

Gravatar plugins are built in most of the blogging softwares. Wordpress above 2.5 holds it and Redmine web based project management application beginning with 8.0

have inbuilt feature for this application

For lower versions of wordpress and readmine we manually need to download and install plugins.

Interesting Things You Should Know About BING

2009-11-17T10:14:00.001+05:30

http://funlinuxfun.blogspot.com/
Microsoft unveiled its search engine Bing. The Bing unveiling can surely be termed as one of the biggest Microsoft launches of the recent times considering the huge stakes it has in the company’s success.There is so much hype on the net about the new search engine Bing by Microsoft on the net that almost every blog has been covering it. Though I doubt anyone can take over Googlejust like that.With Internet gaining importance in the technology landscape, it has become critical for Microsoft to come out with a formidable player which can challenge Google’s growing dominance in the space.

So here are some things you should know about BING.

1.IP ADDRESS TRACKER

The Bing can verify any IP address and can tell you the name of the websites hosted on a particular IP ADDRESS

. To do that simply type,

IP:[ IP Address ]

in the bing search box.

The search result will display the sites hosted on that IP address.

Example type:

IP:70.42.251.42

and you will see sites hosted on this ip address.

2.Remove the background Image on the Bing site

If you are not one of those eye-candy freaks, you can remove the background image on the Bing homepage. Instead of typing bing.com, you can navigate to the site using the following URL,

http://www.bing.com/?rb=0

3.Bing outstripped Yahoo! almost immediately after its launch to take the No. 2 search engine spot.

4.unlike Google, Bing is not a search engine. The software giant dubs Bing as a “decision” engine, rather than a search engine. According to Microsoft, Bing is not just another search engine, but a decision engine that will help people in making decisions.

5.Interestingly, Bing doesn’t return any result for one of the most searched terms from India: sex. However, if you tell the search engine that you’re from the USA, or any one of the European countries (users can easily change country without even logging in), and bing, several links are returned. If you say you are from China or an Arabian country, or Hong Kong or Singapore, again, no luck.

6.Bing offers several features that are not automatically available on Google such as instant excerpts that allow users to see the contents of a page without actually clicking on it and a sidebar detailing related searches.

7.Bing Video seems to have become an instant hit, courtesy its thumbnail video feature. Try searching for a video on Bing Video, once the results appear just hover your mouse over the one you are keen on. Yes, the video starts playing instantly.

8.Another not-so-talked about Bing feature is Save and Share. The feature not only saves your search history, but also allows a user to refine it. Users can delete searches, go back to them, and most importantly save and share them.

9.Everyday, Bing features a different background image.

Which web browser has the least memory utilization

2009-11-17T10:12:00.001+05:30

http://funlinuxfun.blogspot.com/
There must have been time when your system resources gets exhausted and the system gets struck or hangs up.

In order to solve this problem we need to close the running applications or sometimes needs to do an abrupt shutdown.

Have you ever tried to find out the reasons for this problem.

There are many reasons for this problem:

Modern Web browsers are one of them

Firstly what is a web browser?

A Web browser is a software application that interprets the coding language of the World Wide Web and allows for retrieving ,traversing and presenting the information.

Web browsers utilize a lot of memory which contributes to increased response time.

So what to do..we cannot stop using them ,and only what we can do is select the best out of the many market’s web browser , which includes internet explorer, firefox , opera,netscape and many more.

Some tests were carried out by using browsers in similar condition and checking their memory utilization in MB which helps you to choose the best web browser.

The results were plotted on the graph with memory utilization (MB) ox horizontal-axis and browsers on the vertical axis.

So it proves the sluggishness of internet explorer and reasons for why to use firefox and opera.

New Firefox 3.5 RC 3 is even better then opera and its other compilants.

But what surprising is that still the major part of the world follow internet explorer.

I hope this article might give them something to think and boost their system performance.

Web Based Operating Systems:Take Your Desktop Inside Your Browser

2009-11-17T10:07:00.001+05:30

http://funlinuxfun.blogspot.com/

Ever wondered your desktop inside your browser.A full fledged operating system inside the browser.What if you could work with your files and documents anywhere around the world.A beautiful concept called web-based operating systems makes this possible.you just need to sign up and you are done,and just access the desktop anywhere.Below are some of the most popular web based operating systems.

1. EYEOS

A good place to start in your discovery of Web-based operating systems is eyeOS , which is free, open source, and very easy to sign up for. There’s no need to install anything to use eyeOS. Simply sign up with a user name and password to create anaccount, and from that point forward, you have an operating system on the Web, accessible from any browser. eyeOS creates space on its servers to store your operating system settings and any files you create

This is how it looks

2.GHOST

G.ho.st is in some ways even more full-featured and certainly more colourful – than eyeOS. After you sign up, for free, G.ho.st carves out an impressive 5 gigabytes of file storage on its servers for you, and it creates your very own G.ho.st Mail e-Mail account, with 3 gigabytes of storage. Like eyeOS, there’s nothing to install. Once you sign up, you’ll receive a confirmation e-Mail message. Click the activation link inside, and you’re ready to go

3.DESKTOP TWO

Desktop Two is a java-based Web operating system that’s the quickest of all to set up and get going. After a brief sign-up routine, the desktop loads, and you’re ready to start exploring. Desktop Two offers more applications that allow users to create their own presence on the Web than the other major Web operating systems. Along with a word processor and e-mail program, Desktop Two provides a Web site editor and a blogging programme

4.CMY OS

cmyos.com offers a free online operating system/desktop for all users through its open source collaborative network: cmynetworks. Through the open source community, cmyosworks to produce rich applications that are enhance the online experience of developersand browsers alike

OTHER’S ARE

AstraNOS – Picture Windows 98. Then picture an OS X dock. Then picture a night sky. Then throw them all together. You now have a pretty good picture of AstraNOS.
BeDesk – Basic wrapper for other online tools
DoxBoard – Slick WebOS with some basic features
GCOE X – Nice WebOS with a powerful terminal and support for the iPhone
Glide – Online operating system with support for BlackBerry, Palm, Windows Mobile, Symbian and iPhone users
goowy – Great webtop with your own email account (@goowy.com), IM, 1GB of space (via Box.net), and much more
jooce – Slick invite-only online OS
mybooo – Invite-only webtop with a ton of features
myGoya – Nice WebOS with PIM features, a media player, and much more
OOS – Basic online operating system that offers a personal webpage
Parakey – Not much is known about Blake Ross’s newest invention, but we do know thatFacebook liked it enough to purchase it for an undisclosed sum
Psych Desktop – GPLed webtop with a powerful UNIX-like console
Purefect Desktop – Web desktop with a powerful IDE
SSOE – Flash-based webtop a lot of features
StartForce – Powerful WebOS with tons of apps and features makes the descendant ofOrca Desktop a hit
Xindesk – File sync, a powerful API, and much more are included in this great WebOS
Webdesk – This Indian webtop includes 1GB of space, POP3 client, PIM, and a nice modules API
Webdows – We don’t know how long it will take Microsoft to sue these guys, but it’s a real enjoyment in the meantime. It has XP and Vista styles (including a few Vista effects), FTP, file sharing, IM, and much more
Widgets Gadgets – AJAX desktop with tons of apps and a working API
YouOS – File sharing, powerful shell, and 700+ applications are all available with this wildly popular operating system
ZimDesk – Slick WebOS with tons of apps.

How To Set A Password For Grub At Boot Time in linux

2009-11-17T09:56:00.003+05:30

http://funlinuxfun.blogspot.com/
Grub is the linux default bootloader.

Setting up a password in grub is quite an easy task.you can set the password just at boot time to prevent anyone from logging into the system in any mode.

here is how to do it.

Enter the command line and type

#grub-md5-crypt

you will be prompted to enter the password..after entering the password twice you will be provided with a encrypted value as shown below..

copy this encrypted value.

now open the grub.conf file.

#vi /boot/grub/grub.conf

and enter the line

passwd –md5 $1$Tqro5/$pkEbG8f4igg0oZRCoWznb1

where the above encrpted value is the one generated at the time when you entered the password.

also enter

lock

at the end of the red hat container as shown in the figure below.

come out of the editor and then reboot.

#init 6

now at startup you will be asked for the password.

press ‘p’ for password.

and enter the password.

How to Break root password in redhat/linux

2009-11-17T09:53:00.002+05:30

http://funlinuxfun.blogspot.com/
Root account in linux is the supreme account holding all the privildges to manage and configure your system.

Sometimes non-root users wish to login into the root account but doesn’t have the password or in times some bad users change the root password which disables root-user to login ,hence he need to change the password for his account and setup a new password

Here are the all steps to change/break password for root in linux even if previous password is not known:

Step 1:)

When the first grub screen like the below snapshot appears press ‘e’ on linux line entry:

Step2)

After preesing “e” in the previous step the snapshot similar to the below snapshot appears. Move to the line which contains the word ‘kernel’ and press ‘e’

Step3)

Go to end of that line and after rhgb quiet write 1 as in the snapshot below…this means that you are setting your kernel to boot into single user mode also known as the maintenance mode.

Step4)

Then press “enter ” and then ‘b’ to boot the system into run level 1:
Step5)

Now wait for the prompt and write the following command :
#passwd root

Now the password for root account has been changed and try login with the new account:

How To Make A NFS Share

2009-11-17T09:35:00.001+05:30

http://funlinuxfun.blogspot.com/
NFS(Network File System) is a viable solution for sharing disk space between two linux/unix machines/servers. NFS uses a standard client/server architecture. The server portion consists of physical disks containing shared file system and several daemons that make shared file system visible and available for use by NFS clients. NFS clients simply mount the exported file system, known as NFS mounts.
Note: While making a nfs share we should export directories only under / directory and only the local file systems.
Some of the important nfs daemons are:
.rpcbind
.nfs
.netfs
.nfslock
.portmapper
Steps for making a NFS share and exporting the nfs share to the client:

Step1.)Generally all the linux versions comes with the nfs package installed. One can check using:

#rpm –aq |grep nfs

redhat-config-nfs-1.1.3-1
nfs-utils-1.0.1-3.9

Step2.) Configure the /etc/exports file. It is the main nfs configuration file and has two columns.
The first column lists the directories you want to make available to the network. The second column has two parts. The first part lists the networks or DNS domains that can get access to the directory, and the second part lists NFS options in brackets.
eg:
/home 192.168.1.0/24(rw,sync) #this meas that home directory is exported to 192.168.1.0 domain

with read,write permissions.

sync option ensures that file data cached in memory is automatically written to the disk after the completion of any disk data copying operation.

rw can be replaced by ro for making the share read only.

Step 3. ) Use chkconfig command to start nfs services at the boot time
# chkconfig nfs on
# chkconfig nfslock on
# chkconfig rpcbind on

Step 4.)Use the init scripts in the /etc/init.d directory to start the nfs and RPC rpcbind daemons.
#service rpcbind start
#service nfs start
#service nfslock start

Step 5.)Check nfs services by:
#rpcinfo -p #for local machine
#rpcinfo -p hostname #for remote machine

Step 6.)We can check the mounts using:
#showmount -e

Step 7.)When no directories have yet been exported to NFS, use the following command.
#exportfs -a
When adding a shared directory, you can use the following command to export only the new entries.
#exportfs -r

Step 8.)Configuring the nfs client:
Start the nfs daemons on the nfs client also:
Use the chkconfig command to configure the required nfs and RPC rpcbind daemons to start at boot:
#chkconfig nettfs on
#chkconfig nfslock on
#chkconfig rpcbind on

Use the init scripts in the /etc/init.d directory to start the nfs and RPC rpcbind daemons:

# service rpcbind start
# service netfs start
# service nfslock start

Test whether NFS is running correctly:
#rpcinfo -p

Step 9.)On the nfs client add the shared mount entry in the /etc/fstab file:
vi /etc/fstab
#Directory Mount Point Type Options Dump FSCK
192.168.1.100:/home /mnt/nfs nfs defaults 0 0

save and quit from the file

Reload the fstab file by:
#mount -a

Step 10.)Now we can access the nfs share by going into directory in which we have mounted the export on the client side.

How To Configure YUM Server/Yum Repository

2009-11-17T09:33:00.001+05:30

http://funlinuxfun.blogspot.com/
Sometimes one may find himself in dependcy resolution problem while installing rpm packages on linux. Yum(Yellowdog update manager) server is a viable solution to it which holds the repository of linux packages and allows users to take packages .Client can easily install packages with simple commands using the yum installer .Which protocol does yum uses for the tranfer of packages from client to server side?

yum uses ftp protocol for the transfer of packages from client to server side.

Configuring the yum server:

Step1:)Mount the linux dvd/iso to some preexisting directory.

#mount /dev/cdrom /mnt/

Step2:) Intsall the vsftpd package and createrepo package:

#rpm –ivh vsftpd-2.0.5-12.el5
#rpm –ivh createrepo-0.4.11-3.el5

Step3:)Copy the entire DVD to /var/ftp/pub directory:

# cp -rvf /mnt/* /var/ftp/pub/

Step4:)Move to the pub direcorty:

# cd /var/ftp/pub/
#cp Server/repodata/comps-rhel5-server-core.xml Server
# cd Server/
#createrepo -vg comps-rhel5-server-core.xml /var ftp/pub/Server

Step5:)Restart vsftpd service

#service vsftpd restart

Step6:)To enable service start at the boot time type the following command:

#chkconfig vsftpd on
yum server has been established and can be used for downloading the packages.

Configuring the yum client:

Step1:)Create the yum repository file.

#vi /etc/yum.repos.d/ser.repo
enter the following configuration lines.
[Server]
name=any meaningful name
baseurl=ftp://192.168.1.1/pub/Server #enter the ip adress of the yum server
baseurl=file:///var/ftp/pub/Server #if both client and server are same machine
gpgcheck=0
save and exit.
Now you can easily download packages using the yum command:
For more options go to man yum.conf

How To Install And Configure Vyatta As An Internet Gateway

2009-11-17T09:30:00.001+05:30

http://funlinuxfun.blogspot.com/
Vyatta is a popular open source alternative for cisco routerand is a security software which is available as a bootable live CD iso and as a Citrix XenServer & VMWare virtual appliance.

It allows for the easy configuration for routers in your network and is free of cost.

This installation is for all the machines supporting Vmware server or Vmware Workstation and also for the system on which vyatta needs to be installed on base system.
All versions include the current Vyatta feature set and are suitable for evaluation and test environments.

Here are some steps for how two configure vyatta as an internet gateway…

Step1.)For installing vyatta we need a live cd or if using a vmware server/workstation then download vyatta vmware appliance.

Step2.)Download the latest version from here

Step3.)Either use a live cd throughout the process or install it on the hard disk and if using Vmware go to next step. For installing vyatta on hard disk put the live cd and on the system .

Login into the vyatta machine with user root and password vyatta and type install-systemat the prompt to run installation and then the installer launches. The installer is an interactive install script that prompts you for some basic information and confirmation during the install.

Step4.)If using a vmware appliance for vyatta installation first unzip it and then open the .vmdk file through Vmware console open menu. Then turn the virtual machine on. Login into the virtual machine as user vyatta or root with password vyatta for both accounts.

Step5.)Next we need to configure network interfaces in vyatta.

Step6.)Type the following at the command prompt:

vyatta@vyatta:~$ configure
[edit]
vyatta@vyatta# set interfaces ethernet eth0 address
192.168.1.21/24
[edit]
vyatta@vyatta# commit
[edit]
vyatta@vyatta# exit
exit
vyatta@vyatta:~$

Step7.)From another host on the same subnet, ping the interface to ensure that it is up.

Step8.)From a Linux or Windows command prompt, enter the following command
(substituting the IP address you assigned to the interface):
ping 192.168.1.81

If the Vyatta system is reachable, you will see replies from it in response to the
pings.
If so, your system is installed and accessible on your network.

Step9.)vyatta@vyatta:~$ configure

[edit]

vyatta@vyatta# set system host-name R1 ##configuring hostname in vyatta

[edit]

vyatta@vyatta:#commit

vyatta@R1# set interfaces ethernet eth0 address
192.0.2.21/24
[edit]

vyatta@R1# set interfaces ethernet eth1 address
192.168.1.254/24
[edit]
vyatta@R1# commit

vyatta@R1# show interfaces
ethernet eth0 {
address 192.0.2.21/24
hw-id 00:40:63:e2:e4:00
}
ethernet eth1 {
address 192.168.1.254/24
hw-id 00:13:46:e6:f6:87
}
loopback lo {
}
[edit]

Step10.)Define a NAT rule

vyatta@R1# set service nat rule 1 source address 192.168.1.0/24
[edit]
vyatta@R1# set services nat rule 1 outbound-interface eth0
[edit]
vyatta@R1# set service nat rule 1 type masquerade
[edit]
vyatta@R1# commit
[edit]

Step11.)reboot the system and use vyatta as an internet gateway.

How To Add Proxy Server Settings In Mozilla Web Browser

2009-11-17T09:28:00.001+05:30

http://funlinuxfun.blogspot.com/
Sometimes for security reasons one may wish to connect to internet through proxy server

So what is a proxy Server.

Proxy Server is a server that acts as a path between the server and a client. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource, available from a different server.

A proxy server has two main purposes:

To keep machines behind it anonymous.
To speed up access to a resource (via caching). It is commonly used to cache web pages from a web server.

Proxy server can be placed anywhere in between the user local computer and the destination internet.

For connecting system to the internet via proxy server we need to modify setting in the web browser .

Here I am using firefox for this configuration . For other browsers the step may vary slightly but after reading this article it will be easily set .

In the Menu option at the top go to Tools->Options

then go to advanced section

Then go to network tab and add the proxy server’s address in the manual pxoxysettings.

you can add settings for ftp ,http,ssl in the section.

Now enjoy the proxy server settings and be secure on your way to internet browsing.

How To Access And Control A Remote Linux System Using Vncviewer

2009-11-17T09:21:00.002+05:30

http://funlinuxfun.blogspot.com/
Now one can easily enjoy the desktop terminal services of a remote linux machine easily on its own linux/Windows desktop.Vncviewer is the answer to this.

So what is a vncviewer?

Vncviewer is a viewer(client) for virtual network computing.Vncviewer is an Xt-based client application for the VNC (Virtual Network Computing) system. It can connect to any VNC-compatible server such as Xvnc or WinVNC, allowing you to control desktop environment of a different machine.

It is relatively straightforward to display and access a Linux desktop from a system anywhere else on a network or the internet by using Virtual Network Computing (VNC). This can be achieved regardless of whether that system is running Linux, Windows or Mac OS X.. The more impressive thing about this is that it can be set up for free with only a little time and knowledge.

For enabling vnc settings three things are required:

1. A VNC services enabled on the Linux system whose desktop needs to be accessed.

2. A VNC viewer client installed on the system on which you want to display your Linux desktop.

3. A connection between the two systems.

Here are some simple steps that will help you in setting the vncserver and allowing others to have access to your desktop.

Step:1)Firstly you need to install vnc-server rpm on your server system.

Give the following command to install vnc packages:

#rpm –ivh vnc-server-4.1.2-14.el5

#rpm –ivh vnc-4.1.2-14.el5

Step:2)On your Linux system desktop whose desktop need to be accessed, go at the top and click on the System—>Preferences—>Remote desktop

Similar to thepicture below

After clicking on remote desktop a dialog box similar to below one will get displayed:

Here check the first box i.e Allow other users to view your desktop.

There are other options also available like do you want to have password authentication and want to allows the remote system to control your desktop or not.

Step 3:)On the client side install the vnc packages:

To install the vnc package, at the prompt type:

#rpm –ivh #rpm –ivh vnc-4.1.2-14.el5

Step 4:)At the command prompt,just type the following command

#vncviewer

The following dialog box will get appeared.

Enter the ip of the remote machine and enjoy the services

It worked for me like this:

How To configure a samba share on redhat/linux

2009-11-17T09:17:00.001+05:30

http://funlinuxfun.blogspot.com/
Sometimes your network may consists of Windows and Linux system.Samba server is the viable solution for file and printer sharing between linux and windows machines. Samba allows files and printers to be shared by all the systems in a network.
For networks having only Linux system we should go forNFS server.On how to configure NFS share read this
Samba server uses the SMB protocol for sharing files and printers across the network.

For configuration for samba server we need to install samba rpm packages.
For installing package:
# rpm -ivh samba
If your system supports yum installation use:
# yum –y install samba

If your system does not support yum installation you can configure yum server for your network. For

The default configuration file for samba is /etc/samba/smb.conf which allows users to view their home directories as a Samba share. It also shares all printers configured for the system as Samba shared printers.

If you change this configuration file, the changes do not take effect until you restart the Samba daemon with the following command .
# services smb restart.

To specify the Windows workgroup , edit the following lines in your smb.conf file:
workgroup = WORKGROUPNAME
If you want to restrict users to access samba share only form your domain then
In section1:
host allow = your domain ip-address

To create a samba share which can be accessed on windows.Go to the last section of the configuration file for samba and add the following lines

[sharename]
comment = Insert a comment here
path = /home/share/
valid users = tfox carole
public = no
writable = yes
printable = no

You then need to add samba password for the valid users which will access the samba share on the windows machine

#smbpasswd –a username

#service smb restart

To enable service start after the reboot:

#chkconfig smb on

Samba also provides you with a utility called testparm for checking its default configuration file.
# testparm
The above command will show you all the shared folders and printers.

One can also login into the samba share on linux machine with the following command.

#smbclient //ip-address/share-name –U username
Enter the password prompted for and access the samba share.

How to enable anonymous uploads on ftp server in linux

2009-11-17T09:10:00.004+05:30

http://funlinuxfun.blogspot.com/
Anonymous FTP is the choice of Web sites that need to exchange files with numerous unknown remote users. Common uses include downloading software updates. anonymous FTP requires only a username of anonymous and your email address for the password. Once logged in to a VSFTPD server, you automatically have access to only the default anonymous FTP directory (/var/ftp in the case of VSFTPD) and all its subdirectories .You as an anonymous user may be able to download the files but not upload unless configured on your FTP server (VSFTPD server in this case).

Firstly you need to install vsftpd package :

#rpm –ivh vsftpd

If your system supports yum distribution then you can also install using.

#yum –y install vsftpd

Next we need to edit to vsftpd configuration file:

The main vsftpd configuration file is /etc/vsftpd/vsftpd.conf

Open the file using your favourite editor: I m using vim in this case:

# vim /etc/vsftpd/vsftpd.conf

Enable the following two lines:

anonymous_enable=YES

anon_upload_enable=YES

anon_mkdir_write_enable=YES

chown_uploads=YES

Enable the following line and change whoever which is default enrty to root

chown_username=root

Add the following line anywhere in the configuration file:

anon_umask=077

Save and exit

Next we need to create a directory where the anonymous user will upload the files and we need to change the permission and ownership of that directory.

# mkdir /var/ftp/incoming/

# chmod 773 /var/ftp/incoming/

# chown root:daemon /var/ftp/incoming

Restart the service

# service vsftpd restart

To enable it after the reboot

#chkconfig vsftpd on

After doing this step you can allow anonymous users to uploads file onto your ftp server.

How to configure squid proxy server on redhat/linux

2009-11-17T09:08:00.003+05:30

http://funlinuxfun.blogspot.com/
What actually a proxy server means??
A proxy server is a server within a network which provides an extra layer of security and prevents the users direct access to the internet.. Squid is the most widely used proxy server which also provides caching which enablessquid to store requested objects and thus speeding up internet access.

Configuring a squid proxy is an easy task and allows you with wide number of options to configure your users access to the internet .
The best part is that squid is supported on all open source platforms
In this article I will explain on how to configure squid proxy server on redhat / linux.

For configuring squid server we first we need to install squid rpm
Step: 1)
#rpm –ivh squid-2.6.STABLE-5.el5_1.3.i386.rpm

You can also use yum repository for installation . If your system doesnot provide you can configure the yum server for your own

After configuring yum server install the squid rpm using
#yum –y install squid

Step2:) Open the squid main configuration file :

#vim /et c/squid/squid.conf

This is the main configuration file which holds all the squid settings and controls.
Step3:) Squid , by default runs on port 3128. If we need to change the web proxy port.
In the file search for http_port 3128 and change it to http_port 8080.
Now your squid web proxy will run on port 8080.

Step4:) Next you need access rules for the proxy server which are known as ACL to limit users’ ability to browse the Internet. Squid matches each Web access request it receives by checking the http_access list from top to bottom. If it finds a match, it enforces the allow or deny statement and stops reading further. You have to be careful not to place a deny statement in the list that blocks a similar allow statement below it. The final http_access statement denies everything, so it is best to place new http_access statements above it

Here are some examples of the ACL

¬
Restricting web access by IP address
acl mylan src 172.24.0.0/16
http_access allow mylan
Restricting web access by phrase in the url
acl myphrase url_regex phrase
http_access deny myphrase

Step 5:) Like every linux application squid needs to be restarted for changes to the configuration file can take effect..

# service squid restart

For enabling squid startup after the reboot:

#chkconfig squid on

You need to force users to use your proxy server by configuring the proxy setting in the web browser.
Now you can add an extra layer of security and reduce internet bandwidth charges.

How To Configure Dhcp Server On Redhat/Linux

2009-11-17T07:45:00.003+05:30

http://funlinuxfun.blogspot.com/
Dynamic Host Configuration Protocol (DHCP) is a network application protocol used by devices to obtain configuration information for operation in an Internet Protocol network .This protocol reduces system administration and we can add new devices easily within the network.

DHCP also finds application in booting the diskless station.Diskless station sends out RARP signal to dhcp server and the server in response gives the ip-address along with netmask and gateway.
Configuring dhcp server is not a difficult task and dhcp-server can be setup with some easy steps mentioned below

INSTALLATION STEPS:

Step 1. )First of all check whether the package is installed on your system or not.we can check this by :-

#rpm –qa|grep dhcp

A package named dhcp-3.0.5-18.el5.rpm should show up..If it shows up in the result that means the package is installed on your system.Otherwise install it through yum.This can be done by running the following command

#yum install dhcp
or use the following command.
#rpm –ivh 3.0.5-18.el5

Again check with rpm –qa|grep dhcp..The package should show up now.
Step 2.)Linux by default doesn’t put the default dhcp configuration file in location but does it in some other location.

To move to its original location type the following commands
# cp /usr/share/doc/dhcp-3.0pl1/dhcpd.conf.sample /etc/dhcpd.conf

**Location of the default file may vary with linux versions.So one can find the file using the following command:

#locate dhcpd.conf.sample

Step 3.)Edit the dhcp configuration file with your favourite editor:

I am using vi for this:

vi /etc/dhcpd.conf

add the following parameters:
subnet 192.168.1.0 netmask 255.255.255.0 {
option routers 192.168.1.1;
option subnet-mask 255.255.255.0;
option domain-name “thedomain.com”;
option domain-name-servers 192.168.1.1;
option time-offset -18000; # Eastern Standard Time
range 192.168.1.200 192.168.1.250;
next-server 192.168.1.1;
}
Step 4.) Save and exit from the editor.

Step 5. )For other dhcp option go to dhcp man page..
# man dhcp-options

Step 6.) Next we need to create a new .leases file because older versions don’t have the .leases file by default :
# touch /var/lib/dhcp/dhcpd.leases

Step 7.)Start the dhcpd service:

#service dhcpd start

Step 8.)If any changes are made to the configuration settings then we need to restart the service:

# service dhcpd restart

Step 9.)dhcp server is up and running.

Step10.)To enable dhcp service at boot time,go for following command:

#chkconfig dhcpd on

How to setup Nagios Server on Redhat

2009-11-17T03:24:00.005+05:30

http://funlinuxfun.blogspot.com/

1. Don't install nagios using RPM,instead download the source code tarballs of both Nagios and the Nagios plugins (visit http://www.nagios.org/download/ for links to the latest versions).

wget http://osdn.dl.sourceforge.net/sourceforge/nagios/nagios-3.0.3.tar.gz

wget http://osdn.dl.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.11.tar.gz

2. Create Account Information

Become the root user.

su -l

3. Create a new nagios user account and give it a password.

/usr/sbin/useradd -m nagios

passwd nagios

4. Create a new nagcmd group for allowing external commands to be submitted through the web interface. Add both the nagios user and the Apache user to the group.

/usr/sbin/groupadd nagcmd

/usr/sbin/usermod -G nagcmd nagios

/usr/sbin/usermod -G nagcmd apache

5. Extract the Nagios source code tarball.

cd ~/downloads

tar xzf nagios-3.0.3.tar.gz

cd nagios-3.0.3

Run the Nagios configure script, passing the name of the group you created earlier like so:

./configure --with-command-group=nagcmd

6. Compile the Nagios source code.

# make all

Install binaries, init script, sample config files and set permissions on the external command directory.

# make install

# make install-init

# make install-config
# make install-commandmode

7. Customize Configuration

Sample configuration files have now been installed in the /usr/local/nagios/etc directory. These sample files should work fine for getting started with Nagios. You'll need to make just one change before you proceed...

Edit the /usr/local/nagios/etc/objects/contacts.cfg config file with your favorite editor and change the email address associated with the nagiosadmin contact definition to the address you'd like to use for receiving alerts.

vi /usr/local/nagios/etc/objects/contacts.cfg

8. Configure the Web Interface

Install the Nagios web config file in the Apache conf.d directory.

make install-webconf

root@lvs2 nagios-3.0.3]# make install-webconf

/usr/bin/install -c -m 644 sample-config/httpd.conf /etc/httpd/conf.d/nagios.conf

8. Create a nagiosadmin account for logging into the Nagios web interface.

htpasswd -c /usr/local/nagios/etc/htpasswd.users nagiosadmin

Restart Apache to make the new settings take effect.

service httpd restart

9. Compile and Install the Nagios Plugins

Extract the Nagios plugins source code tarball.

cd ~/downloads

tar xzf nagios-plugins-1.4.11.tar.gz

cd nagios-plugins-1.4.11

10. Compile and install the plugins.

./configure --with-nagios-user=nagios --with-nagios-group=nagios

make

make install
Start Nagios

11. Add Nagios to the list of system services and have it automatically start when the system boots.

chkconfig --add nagios

chkconfig nagios on

Verify the sample Nagios configuration files.
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

If there are no errors, start Nagios.

service nagios start

12. Object configuration files

As mentioned, when the configuration files are split up, Nagios reads the data from these files in order for it to process host and service checks across the network. Before I begin, detailed documentation of all of the options for the template based objects are located at the website.

# cd /usr/local/nagios/etc/objects/

# touch hostgroup.cfg hosts.cfg services.cfg

# vi localhost.cfg

Copy the Services Definitions

# vi services.cfg

Paste the Services Definitions

#vi localhost.cfg

Copy the Host Definitions

#vi hosts.cfg

Paste the Host Definitions

#vi localhost.cfg

Copy the Host Definitions

# vi hostgroup.cfg

Paste the hostgroup Definitions

Setting up nagios.cfg

[me@rhel ~] cd /etc/nagios

[me@rhel nagios] mv localhost.cfg localhost.cfg_org

Turn on the allow commands to be executed from the CGI web interface.

[me@rhel nagios] vi nagios.cfg

# OBJECT CONFIGURATION FILE(S)

cfg_file=/etc/nagios/contacts.cfg

cfg_file=/etc/nagios/hostgroups.cfg
cfg_file=/etc/nagios/hosts.cfg
cfg_file=/etc/nagios/services.cfg
cfg_file=/etc/nagios/timeperiods.cfg

# EXTERNAL COMMAND OPTION

check_external_commands=1

# EXTERNAL COMMAND CHECK INTERVAL

command_check_interval=1

I have my sample config to download:http://www.turboupload.com/files/get/fS98EGYNwt/sampleconfig.odt

How to enable and use Desktop Effects (Compiz) in openSUSE11.0

2009-11-16T23:59:00.003+05:30

http://funlinuxfun.blogspot.com/
openSUSE 11.0 comes preinstalled with Compiz and Compiz-Fusion 0.7.4 pre-installed.

Enable Compiz/ Desktop Effects

To enable Compiz, referred as Desktop Effects in openSUSE 11.0

From Applications – Configure Desktop – Desktop, tick the box for “Enable Desktop Effects” and click Apply. This should enable Desktop Effects / Compiz on your openSUSE.

Alterntaivelty, you can enable from

Application – Utilities – Desktop – Desktop Effects – select the checkbox for “Enable Desktop Effects” and close.

Here you can also, select a preset profile for your Desktop Effects ranging from minimal to Ultimate.

Once enabled, we are all set to start using desktop effects or Compiz on openSUSE 11.0.

Now, that we have installed and enabled Desktop Effects (Compiz) in our openSUSE, how do we use it?

Compiz Fusion / Desktop Effects enables a bunch of plugins by default and one of them is the Desktop Cube. The Destop Cube shows the multiple workspace on your desktop as a Desktop Cube. Imagine your Desktop as your cube and each side of the cube is a workspace in your multiple worlspace desktop and thats exactly is a desktop cube. This cube can also be unfolded and shown as a strip of slides where each slide is a desktop workspace.

Prior to enabling and using Desktop Cube, the most important aspect of the Desktop Cube are your keyboard and mouse (or touchpad in case of a laptop)

Apart from the standard special keys on your keyboard like keys there are few others, you need to familiarise with. They are

Super Key – “Windows Key” on your keyboard (if found)

Mouse Key mappings

Button1 – Left-click button on your mouse
Button2 – Right-Click button on your mouse
Button3 – Middle click button or clickable wheel on your mouse
Button4 – Forward scroll on the wheel of your mouse
Button5 – Backward scroll on the wheel of your mouse

Enable Desktop Cube

Let’s first see how to enable the Desktop Cube and the Rotation. The Desktop Effects or Compiz Fusion plugins can be enabled from CompizConfig Settings Manager (ccsm). This can be started from Applications – Applications – CompizConfig Settings Manager or can be started from the terminal as follows:

opensuse11:~ # ccsm

This should launch the CompizConfig Settings Manager

Here, select the checkboxes for “Desktop Cube” and “Rotate Cube”. This enables the Compiz Desktop Cube.

Start Desktop Cube

Lets have a preview, to start the Desktop Cube,

1. Press and hold the keys + on the keyboard.
2. While holding the keys, click, hold and drag the Button1 (left click button on mouse). Drag in any direction to view the cube

You should see the cube in action, each side of the cube is a desktop workspace. How is that for a start????

Almost everything about the cube is customizable, from the image on top of the cube or the background image of the cube (Skydome as in Compiz). To customize the Desktop cube, from the CCSM, click the Desktop cube to open the properties.

In the properties window,

the General tab allows you to change the key mapping

the Appearence tab allows to customize the appearence, change images for cube top and background (SkyDome)

the Behaviour tab allows to change the cube behaviour. For instance, to view the cube from the inside

the Transparent Cube tab allows to change the transparency setting.

Lets have a look at some of the effects of the Desktop Cube

Unfold the Cube

To unfold the cube and show it as a strip of slides with each slide representing one side of a Cube

1. Press and hold +. This should bring up the strip.

2. To move the strip, while holding the above the keys, press the or the to move in that direction. You may press and hold this key (say for a running strip

Inside Cube

By default, the cube is viewed from the outside of the cube. lLets for a change look the desktop cube from the inside.

1. Bring up the properties for Desktop Cube and click Behaviour tab.
2. Select the “Inside Cube” check box.

Now bring up the cube as earlier and see the difference

Desktop Cube in Sphere or Cyclinder

Again, the Desktop Cube is by default viewed in square edges where each side is a desktop workspace. Why not view it as a cyclinder or a Sphere. Possible??? Why not?

1. Enable the “Cube Reflection and Deformation” plugin under Effects in CCSM.
2. Click on it to bring the properties and click the “Deformation” tab
3. Select Cyclinder or Spehere from the Deformation listbox.

Now, bring up the cube and see the different… mind blowing!!!

This effect will also be seen when you unfold the Desktop Cube

3D Windows

All is great so far…Why not a 3D effect onto the cube??

Enable the “3D Windows” plugin under effects.

Bring up the Desktop Cube, you should see the active windows in your cube are shown seperately as a 3D window.

Reflection

Enable the Reflection plugin under effects in CCSM and you should see the reflections on the window when the cube is evoled again. This is the reflection of the image selected. To change the image, click on “Reflection” plugin and choose the image of your choice.

NOTE: On unsupported display/video cards (say Intel 965GM), thus can crash your display.

Hope you had a great preview of your compiz/Desktop Effects. I couldn’t workout a way to capture these while in action than to use my cameras and hence no screenshots of Desktop Cube in action.

Using `cvsd’ to setup cvs pserver

2009-11-16T23:31:00.003+05:30

http://funlinuxfun.blogspot.com/
CVS was designed to use `xinetd’ to startup service. But now most Linux distributions do not install xinetd by default, and configuration of CVS is somewhat complicated. `cvsd‘ is a wrapper program for CVS in pserver mode, it can startup CVS as a standalone daemon, under a special uid/gid in a chroot jail. It is relatively easy to use cvsd and its configuration file to setup CVS repositories.

In this article, I will describe how to setup a cvs pserver step by step.

1. Installation of cvsd package

For RPM-based distributions, you may download precompiled RPMS from this site:

cvsd-1.0.14-1.i386.rpm
cvsd-1.0.14-1.src.rpm (source)

For other distributions, you may download source tarball here, compile and install it yourself.

2. Configuration file /etc/cvsd/cvsd.conf

Check cvsd’s configuration file /etc/cvsd/cvsd.conf. Something should be mentioned:

RootJail: the location of the chroot jail cvs should be run in. The default value should like

RootJail /var/lib/cvsd

For RPM-based installation, the installation process should have initialized this directory for you, by the command

# cvsd-buildroot /var/lib/cvsd

If the directory is not initialized yet, or you change `RootJail’ to another directory, you need to use the command `cvsd-buildroot’ to initialize it by hand.
Uid and Gid: the user and group cvsd should be run as. The default values:

Uid cvsd Gid cvsd

For non-RPM based installation, you need to create them by hand.
Repos: paths to repositories, one repository per line. Every path is relative to RootJail and begins with a `/’. For example:

Repos /coolsoft Repos /hotsoft

3. Creation of repositories

To create a repository, for example, `coolsoft’, use the command:

# cvs -d /var/lib/cvsd/coolsoft init

The command will create a directory /var/lib/cvsd/coolsoft and a CVSROOT tree in it.

If you allow users to create top level directories in this repository:

# chown cvsd:cvsd /var/lib/cvsd/coolsoft

Edit the file /var/lib/cvsd/coolsoft/CVSROOT/config and modify the `LockDir’ option:

LockDir /tmp/coolsoft

The directory is relative to `RootJail’, /var/lib/cvsd. Create the directory:

# mkdir /var/lib/cvsd/tmp/coolsoft # chown cvsd:cvsd /var/lib/cvsd/tmp/coolsoft

Now create users that can access this repository and set the passwords:

# cvsd-passwd /var/lib/cvsd/coolsoft jack

If you want anonymous access to your repository, create a user named `anonymous’ or `anoncvs’, and leave the password blank:

# cvsd-passwd /var/lib/cvsd/coolsoft anoncvs

Create a new file /var/lib/cvsd/coolsoft/CVSROOT/writers:

# touch /var/lib/cvsd/coolsoft/CVSROOT/writers

to protect write access to the repository. Without this file, all users have write access! Add users you want write access to this file, one user per line.

Optional, create top level directories in your repository that will hold files committed:

# cd /var/lib/cvsd/coolsoft # mkdir client server # chown cvsd:cvsd client server

4. Startup cvsd and test your repositories

To startup cvsd, use the command

# /etc/init.d/cvsd start

To test the new repository:

# cvs -d :pserver:jack@myhost.at.office/coolsoft login # cvs -d :pserver:jack@myhost.at.office/coolsoft co client