Best Interview I Have Ever Attended

Its been long time that I blogged here. The reason for this post is to share my experience of an interview. If you people think this is irrelevant, please feel free to comment at comment section, depending on your comments i will keep or remove this post. Because its just a general post not related to admin work much. OK lets come to actual point.

A couple of weeks back i got a call from a company, they asked me to come down to the interview with all the media required. The media which i have taken includes.
1.RHEL5.4 which is 64bit version
2.Oracle 10g
3.JBOSS(For those who don't know about Jboss. Its a application server like TOMCAT, Web-sphear etc. used to serve the content through web).

In the same call they informed its totally a practical interview. I have to configure and show all the configuration on a given Blade Centre which contain six blade servers in it.
Some background about that Blade-centre.
1. It costs nearly 46Lacks. Yes you red properly it costs 46 lacks INR(Rs4600000)
2. Its having 6 blades(nothing but 6 blade servers)
3. SAN box attached to it(total capacity of 4.5TB)
4. A seven layer switch(I don't know much about this. I have to explore on this)
5. A backup tape-drive for this SAN backups.
6. A common DVD ROM, Keyboard, Mouse, Monitor for all the six blade servers
7. Four to six usb devices(i did not observed properly)
8. Eight LAN ports

So all these are included/integrated in to a box which be like big TV box(search for blade-centre in Google for exact look).

Why we require this blade server why cant we use separate six high end servers?
Ans : Let me put it in this way. In most of the DC(Data Centre) space, power, cooling are always concerns. So IBM came with a solution to resolve all these problems by implementing Blade canter/server.

Each blade server looks like a closed laptop when we take it out from Blade center box(its very much easy to insert/remove blade-server from blade centre)

What this each blade server contains?
Ans : 1. HDD with hardware RAID1 on implemented with 132GB(so total space with out RAID will be 132*2=264GB).

2. RAM of 16B(There are four slots, each contains 4gb. These RAMS are placed on the mother board in such a way that it will consume less space and good for cooling).

3. A fiber converter is there which have high capacity data transfers.

4. Two NIC/LAN cards(These are integrated on to board it self).

5.A switch/button for getting display.(Here we have to remember one thing. As there is only single display, mouse, keyboard which are to be shared). So if you press this switch on blade server one all these devices are now part of blade server one.

6. A switch/button for getting DVD rom for this blade server.

7. A power switch to switch of this single blade server
That's it.

Ok I think this introduction is enough for those people who don't know what is a blade center or server. Please feel free to ask any queries on this. If you still not clear.

The test/Interview goal is to :
1. Install OS(RHEL5.4 64 bit).
2. Yum Server(on one of the blade server so that remaining servers will take yum repo from that server).
3. Network configuration(like IP addressing and host-name).
4. Jboss to be installed/configure on all the servers.
5. FATware to be install/configure on all the servers.
6. Oracle on two blade servers.
7. High availability cluster for this Oracle.
That's the end of the Interview.

They have assigned an Experienced Network/Hardware engineer to me who really assisted me in all hardware related stuff. He is really having good knowledge on all the server hardware and he is a nice guy.. :)

His work is to initialize all the blade servers, configuration of hardware RAID1 and other network related stuff.

We started with Redhat installation on one machine. We did successfully. I thought we no need to install OS on remaining blade servers because I thought of replacting this HDD on remaining HDD(Because all the servers are HDD are hardware RAID1) but bad luck that IBM blade-centre model will not support this. So we installed OS on each server one by one. I thought/show him how to create partitions and install OS after second server installation. He only taken care of installing OS on remaining blade servers. Mean that time I have started configuring Yum on blade server1, Configured network related stuff, installed some software required by oracle, Jboss etc. By using Yum server. Once these things are done I did the same thing for reaming servers. All these tasks taken most of my time :(

Then we installed Oracle on server one and two, after that Jboss on all the 6 blade server. Once all the main configurations are done at last we tried to implement cluster for the oracle(we implemented Heartbeat cluster for this one..)

This total process taken nearly 12 hours from 9Am to 9Pm.

I want to include more info but i felt its too big.
Please comment on this:-)

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How To : FTPS Server Configuration

I used to astonish all the time when I see the FTP package name. vsftpd which abrivated to Very Secure File Transfer Demon(vsftpd). But when we see the security prospective of this package there is no much security included with this package. I mean when you login to server the credentials are transfered in plain text. So by defalut root user is not allowed to login to ftp server.

To eliminate transfering data in plain text and to encrypt the entire transmission we can take help from open ssl to generate a certificate and use SSL certificate when communicating with FTP server. This is nothing but a FTPS server.

Some file transfers you should know are.
1. TFTP(Trivial File Transfer Protocol which uses UDP for transmission) –high data rates/not secure
2. (This protocol uses SSH in backend, so you no need to run an FTP server) –secure
3. FTP(This is normal ftp transfer which uses TCP) –not secure
4. FTPS(FTP+SSL certificate to encrypt data transmission)
5. Over SSH(this is a kind of ftp tunnel on SSH protocol)

In this post we will see how you can configure SSL certificate for VSFTPD.

Step1 : Check the following packages on the server and if they are not install please install them.
#yum install openssl
#yum install vsftpd

Step2 : Generate rsa key in /etc/vsftpd folder as below.
#cd /etc/vsftpd
#/usr/bin/openssl req -x509 -nodes -days 365 -newkey rsa:1024 -keyout vsftpd.pem -out vsftpd.pem

The clipped output for your reference
[root@v-itig42 vsftpd]# /usr/bin/openssl req -x509 -nodes -days 365 -newkey rsa:1024 -keyout vsftpd.pem -out vsftpd.pem

Generating a 1024 bit RSA private key

....................................................++++++

..........................................++++++

writing new private key to 'vsftpd.pem'

-----

You are about to be asked to enter information that will be incorporated.
into your certificate request.

What you are about to enter is what is called a Distinguished Name or a DN.

There are quite a few fields but you can leave some blank.

For some fields there will be a default value,

If you enter '.', the field will be left blank.

-----

Country Name (2 letter code) [GB]:IN

State or Province Name (full name) [Berkshire]:Andhra Pradesh
Locality Name (eg, city) [Newbury]:Vijaywada
Organization Name (eg, company) [My Company Ltd]:Linuxnix Systems Limited
Organizational Unit Name (eg, section) []: IT admin Group
Common Name (eg, your name or your server's hostname) []:ftp2.linuxnix.co.in

Email Address []:surendra@linuxnix.co.in

Step3 : Once the Certificate is generated, certificate is kept in /etc/vsftpd folder. We have to provide this entry in vsftpd.conf along some ssl configurations.

Step4 : Edit vsftpd.conf and give enteris at the last of the file.
#vi /etc/vsftpd/vsftpd.conf
#For SSL on specify yes to below option.
ssl_enable=YES
# To allow anonysonomous users to use SSL
allow_anon_ssl=YES
# if you want local users to use both ssl as well unsecure way of transmission of data plz specify no to below option.
force_local_data_ssl=NO
#If you want to allow all the login credentials which are transmitted should be sent with encryption #pleas use below option to force them to use only ssl connection at the time of login.
force_local_logins_ssl=YES
# Permit TLS v1 protocol connections. TLS v1 connections are preferred
ssl_tlsv1=YES
# Permit SSL v2 protocol connections. TLS v1 connections are preferred
ssl_sslv2=NO
# permit SSL v3 protocol connections. TLS v1 connections are preferred
ssl_sslv3=NO
#Please pecifies the location of the RSA certificate to use for SSL encrypted connections
, which we #created some time back.
rsa_cert_file=/etc/vsftpd/vsftpd.pem
Now save and exit the vsftpd file

Step5 : Restart the vsftpd service.
# service vsftpd restart
Shutting down vsftpd: [ OK ]
Starting vsftpd for vsftpd: [ OK ]


Start accessing the ftp server with user name credentials with filezila or some other FTP clients which will support SSL/TSL. If you want to access ftps sites through browsers its not possible. We have to have addon called fireftp. Then only we can access ftps:// site. Here in this example I used filezila.

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Converting Sun Virtualbox vmi file To Vmware vmdk file

This article show you how to convert Sun Virtualbox vmi file to Vmware vmdk file. Recently I have started using Ubuntu as my desktop in my company. And installed Sun Virtualbox for test VMs. But most of the people have vmplayer installed. So they donot know how to use this vmi images on a windows box. So here is a solution for converting those vdi image files to VMware .vmdk images.

When we install Sun Virtualbox we have so many command lines tools installed along with it. One good tool is VBoxManage, Please remember commands in Linux are case sensitive. So if you try to type vboxmange it will not work. You have to type exactly as VBoxManage.

Step1 : Convert from vdi to raw.
#VBoxManage internalcommands converttoraw /data/Vm-images/ubuntu-vm.vdi /data/Vm-images/ubuntu.raw

Step2 : Now install qemu, which is used to convert .raw files to .vmdk
#apt-get install qemu

Step3 : Convert .raw files to .vdmk using qemu-img command
#qemu-img convert -O vmdk /data/Vm-images/ubuntu.raw /data/Vm-images/ubuntu.vmdknow try to access this .vmdk file using your VMware workstation or VMware player.

So what about viseversa?here there are two methods are there
1. By default your Sun Virtualbox will support .vmdk vmware images.
2. If its not supported use the following way.

Step1 : Use again qemu-img to convert .vmdk disk to .rawqemu-img convert ubuntu.vmdk /tmp/ubuntu.raw

Step2 : VBoxManage convertdd /tmp/ubuntu.raw ubuntu.vdiplease share your thoughts.

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