The basic syntax of grep is:

grep pattern target_file

OK, now that we have the theory, let’s see some practical examples.

1. Searching for a text string in one file

grep 'root' /etc/passwd

2. Searching for a string in multiple files

grep 'root' /etc/*

The wild card matches all files in the /etc/directory

3. Showing matching line numbers (-n)

grep -n 'root' /etc/passwd

4. Counting the number of matches (-c)

grep -c 'root' /etc/passwd

5. Recursive search (-r or -R)

grep -r "string" /home/

Search for the string ‘string’ in all the files in the home directory and all its subdirectories.

6. Invert match (-v)

grep -v 'root' /etc/passwd

Displays the lines which does not matches the given string

7. Display only the file names which matches the given pattern (-l)

grep -rl "string" /home/

8. Search for full words not partial matches within words (-w)

grep -w "fullstring" /home/

9. Show only the matched string, not the whole line (-o)

grep -o "fstring" /home/

10. Advanced usage of grep

- find out process pid

ps aux | grep someprocess

- multi patterns

grep -iE "(something|somethingelse)" file

- determine which services are enabled at boot

chkconfig --list | grep $(runlevel | awk '{ print $2}'):on

- search for IP addresses

grep -Eo '([0-9]{1,3}\.){3}[0-9]{1,3}' /var/log/maillog

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The process of installation and configuration on one of our Cloud VPS accounts is quite simple and takes less than 5 minutes to complete.

Log in to your server as root, download the software from: http://www.rfxnetworks.com/apf.php (the newest version at the time of writing this article was: 0.9.7_2) unpack it and install it by executing the following commands:

cd /root/

wget http://www.rfxnetworks.com/downloads/apf-current.tar.gz 

tar -zxvf http://www.rfxn.com/downloads/apf-current.tar.gz

cd apf-9.7-2

./install.sh

Below is the general configuration of APF on servers with CentOS and cPanel. For more detailed information on every feature the firewall has, see the README file supplied with the APF sources.

Edit the APF configuration file:

vi /etc/apf/conf.apf

press ‘i’ to enter Input mode.

These are inbound TCP ports that need to be open in order to run cPanel behind a firewall: 20,21,22,25,26,37,43,53,80,110,113,143,443,465,873,993,995,2077,2078,2082, 2083,2086,2087,2095,2096 and 3306 (open port 3306 only if you want to remotely access to the MySQL database server).

Find the line starting with ‘IG_TCP_CPORTS’ and modify it to:

IG_TCP_CPORTS="20,21,22,25,26,37,43,53,80,110,113,143,443,465,873,993,995,2077,2078,2082,2083,2086,2087,2095,2096,3306"

Find the line starting with ‘IG_UDP_CPORTS’ (inbound UDP ports that must be open) and modify it to:

IG_UDP_CPORTS="53"

Also modify the following lines:

IG_ICMP_TYPES="0,3,5,8,11,30"

EG_TCP_CPORTS="21,25,37,43,53,80,443,873,2089" 

EG_UDP_CPORTS="20,21,53,873"

where ‘IG_ICMP_TYPES’, ‘EG_TCP_CPORTS’ and ‘EG_UDP_CPORTS’ are inbound ICMP ports, outbound TCP ports and outbound UDP ports that must be open to run cPanel behind a firewall.

Start APF using the following command:

/usr/local/sbin/apf -s

Test the firewall with a port scanner like nmap or using a similar tool and if everything is OK, change DEVEL_MODE=”1″ option in the ‘/etc/apf/conf.apf’ configuration file to 0.

Restart APF for the changes to take effect using:

/usr/local/sbin/apf -r

To autostart APF at boot time execute the following command:

chkconfig --level 2345 apf on

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#!/bin/bash
array=(100 101 102 105)
for (( i = 0 ; i < $((${#array[@]}-1)) ; i++ )); do
if [ $((${array[$i]}+1)) -ne ${array[$(($i + 1))]} ] ;then 
    M_NUMBER="$((${array[$i]}+1))"
    break
fi
done

echo $M_NUMBER

Explaining the code:

$((${#array[@]}-1)) – number of array elements minus one

$((${array[$i]}+1)) – i-element of the array plus one, starting from the first element

${array[$(($i + 1))]} – i+1 (next) element of the array, starting from the second element

If the next element is not equal to previous element plus one, the script will print the missing number – $((${array[$i]}+1))

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But how so?Well, one pretty obvious answer is the total eradication of the dependence on hardware. Sure, hardware is still necessary to interact with the cloud, but hardware becomes only a tool, a medium, a channel, and nothing more. This means that relying on your Mac or PC or any kind of hardware will be a thing of the past. You can now use any kind of hardware to access your data as long as there is Internet connection.

In the greater scheme of things, for webmasters and cloud hosting customers, cloud computing and cloud hosting will change the way they buy hosting plans as cloud computing are no longer restricted by physical space and hardware limitations. This means that cloud users can have access to a massive data storage system and a massive amount of resources that can make performance as robust as possible. Again, these resources are not dependent on hardware and are therefore easier and less costly to put together. In other words, cloud computing can also revolutionize the way we think about computing by giving the web enough room to grow and enough space for further performance improvements.

Cloud computing will also further revolutionize the way we think about computing by making computing synonymous with the Internet. While in the past, computing is one thing and the Internet is just one part of it, the biggest change that cloud computing will bring is that it will drive the importance of the Internet even further. It will make the Internet much more important than it currently is. This does, however, bring some drawbacks, such as the vulnerability of the system to problems pertaining to the Internet connection. This means that if your connection is poor, you will encounter problems. But it will not, in any way, endanger your files or make them inaccessible from another location, where the Internet connection is better.

So it seems clear that cloud computing will revolutionize the way we think about computing. It’s not a flawless system, but it undeniably changes a lot of things we used to know about computing. First, it makes computing less dependent on hardware. Second, it gives computing space for growth. And third, it makes the Internet even more important. Based on these changes, we start to get a glimpse of where cloud computing is planning to take the world of computing or, in other words, where the future of computing is headed.

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As cannot be avoided, cloud hosting does have its drawbacks, with one of it being high initial costs for setup. But based on real-life experiences of small to medium sized businesses, cloud computing, even at its current state, has already brought various advantages, such as reduced computing costs and improved efficiency. Both are advantageous during a recession period. In fact, a number of SMEs who have taken a leap of faith and invested in cloud computing systems have testified to enjoying great benefits from it.

The Pros

Savings on upfront costs. According to early users of the cloud, the new cloud hosting option helped them save on their upfront costs by moving their e-mail, web hosting, and virus protection – basic hosting fare – to the cloud.

Savings on utility bills. Due to the absence of physical hardware to run, cloud hosting also helped companies save on their power bills.

Eliminates hardware upgrades and maintenance. Again, since there is no need to invest in hardware, there is also no need to upgrade and maintain hardware. Hardware requires a lot of maintenance, otherwise it will cease to work properly. Thankfully, cloud computing has eliminated this problem.

Protection from server crashes. Physical servers are highly vulnerable to crashes, which translate into downtime and additional costs for data recovery, if needed. Cloud computing helps prevent such problems by keeping data in the cloud, not dependent on any physical hardware, which may eventually run into physical problems.

Improved productivity. Due to the consistency and the resiliency of the cloud, it tends to result in an improved company productivity.

All-around access from anywhere. The cloud allows all team members or company employees to access data files from any location, as long as there is connection.

Secure storage. Cloud computing is not as vulnerable as traditional hosting options, making it the more secure choice of storage.

Easier internal collaboration. The robustness of cloud computing and its flexibility and convenience all help colleagues collaborate more easily.

The Cons

Not 100% immune to security breaches. As with any kind of hosting platform, cloud computing is not 100% immune to breaches in security. Keep in mind, however, that this should not be taken solely as a point against the cloud since all forms of computing have their own vulnerability. The cloud, in fact, has managed to minimize its vulnerability.

Level of privacy from cloud companies. The one major problem companies have with cloud computing is that they need to turn their data over to third parties.

Dependence on Internet connection. The cloud is rendered unusable if there is no Internet connection. This is a major drawback that is keeping many interested users from taking the final plunge to cloud computing.

Data loss due to inexperienced, low-quality cloud hosting services. The quality, reliability, and security of cloud computing is currently still dependent on which cloud hosting provider one chooses. This means that if you choose a low quality provider, there is always the risk of losing data or encountering some other problem.

The Conclusion

This comparison shows that cloud computing has more advantages than disadvantages. It is therefore simply a matter of deciding whether you are willing to accept the cons in order to enjoy the pros.

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After it was decided that a VPS was better, the debate moved on to whether a VPS should be Windows-based or Linux-based. The consensus, this time, was that a Linux VPS was better as it provided greater flexibility, more reliability, and surer stability.

And now, the debate has moved on yet again, this time to whether a cloud VPS is better than an ordinary VPS, either Windows-based or Linux-based.

A cloud VPS is a virtual private server located on the cloud, which means it is always available as long as the Internet connection is up and running. While a VPS can give you robust performance and more resources, it is undeniable that the benefits of a cloud VPS are far greater especially for businesses.

Here are some of the reasons why you should move from an ordinary VPS to a cloud VPS:

100% uptime for networks. Your hosting package as well as the entire network running on the cloud will always be up and available to other members of the network. This means that even if you’re not in front of your computer, other members of the team or company can access your important company files through the cloud.

Your site will be constantly up. There is nothing more disastrous for a business, especially web-based or e-commerce businesses, than to have their company websites be unavailable. This can translate to lots of wasted opportunities, opportunities that would have otherwise translated into lots of income for the company. With a cloud VPS, though, your site will always be up, ready to accept customers and make money for your business.

You have unlimited growth potential. A cloud VPS and a regular VPS are the same in many ways, but one of the ways in which they differ is that, in a cloud VPS, resources are on-demand. So if you need more, you will easily be able to get more.

Pay for what you need. In cloud hosting, you will only pay for the resources that you actually use up. In regular VPS hosting, this is not possible because hardware has to be setup and has to have limits. Thus, the two have different payment schemes. In an ordinary VPS, you will pay predictable similar costs every month. In a cloud VPS, however, you will be billed for each minute. This means you will not pay for resources you didn’t use in the first place.

Cloud VPS is instantly scalable. Both cloud VPS and ordinary VPS are scalable. The difference is, an ordinary VPS can be quickly scalable by purchasing additional resources such as memory, disk space, and processor speed, but a cloud VPS is ‘instantly’ scalable, without the need for purchasing anything. You can use up as much bandwidth, CPU space, and memory as you need then be billed accordingly.

The ideal hosting plan for any company is not a specific choice between these two, but a relative choice depending on what the company requires.

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The term ‘cloud vps‘ refers to fully redundant and self-healing virtualized servers with automatic fail-over capabilities accessible from anywhere on the Internet.

The actual term ‘cloud’ is coming from telephony services in telecommunication companies who until the 1990s provisioned mainly dedicated point to point data circuits. Then they began providing Virtual Private Network (VPN) services with corresponding quality of service but at a greatly reduced price.

Cloud hosting is based on the most advanced Cloud computing technologies that allow virtually unlimited number of physical servers to act as a rock solid efficient, stable, secure and reliable system intended to deliver more flexibility to clients who can create and destroy their own cloud virtual servers or increase/decrease their cloud virtual server computing resources almost instantly as needed. It is an emerging technology that enables the pooling of large number of separate physical servers and computing devices together so that they act like one, and websites or consumers resources (active processes, user applications) pull resources for computing from the pool as a whole.

Other hosting solutions (shared hosting, conventional VPS hosting or dedicated server hosting) rely on one server machine only where all CPU, RAM and disk resources are limited to the host server resources itself, while cloud hosting is flexible and fully redundant because it is guaranteed by many physical servers. The cloud technology allows higher security of data and seamless customization, full wide range of operating systems for your needs, databases, server software and applications to fit your requirements. Addition of extra resources to a particular cloud VPS, such as CPU cores, RAM, primary and backup disk space is easy and instant and thus provide scale out computational resources whenever required to that cloud VPS, without compromising the stability and performance of other cloud servers or even the entire cloud hosting system.

The main benefits of the Cloud VPS Hosting are:

• Highest level of performance, self-healing and auto fail-over at affordable prices
• Guaranteed amount of server resources (CPU, RAM, Disk) at any given point in time
• Fully redundant data storage
• No single point of failure
• Flexible pricing

As computer technology continues to advance so do the capabilities of the cloud hosting. As faster servers become available and storage area networks (SANs) continue to grow in size, the cloud hosting industry will also continuously enhance its services and standards. The improvements in the computer technology will most likely demonstrate on the reduction of time it takes to execute a simple computing process. It goes without saying that the data processed in an hour today can be done in just a minute or even seconds in the future. Faster processors, RAM, disk drives and network connections will be the main factors of this advancement.

The Cloud VPS hosting shall become the primary hosting choice of companies and individuals due to the excellent dynamic and versatile features it offers, due to its flexibility, unbeaten reliability, ease of management and use, cost-effectiveness and price-performance ratio it offers. If you are a website owner and want to give your precious visitors the best ever site browsing experience by making it more time efficient, then you may need to think about it and move to a cloud VPS.

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