Friday, 23 December 2016

There may come a point in time where you need to change the shared IP address of a server, with little to no interruption in service for your users.

This guide will show you how to change the shared IP of your cPanel server with the method I’ve used in the past. This is intended for intermediate to advanced administrators that have some basic knowledge of cPanel and networking. This will only update the main IP of your server, and will not affect accounts that have dedicated IPs or SSL certificates.

Changing the Shared IP Address of a Live Server

Update your TTLs

The first thing you need to set your zone TTL’s on the server to a lower value a day or two prior to changing the IP, so the caching period is lower. Caching DNS servers should be configured to use the TTL value, and while all may not be configured to work this way, you should prevent inconvenience to most of your users by configuring the value as low as possible – usually to 3200.

There may be some methodical science behind this that you can come up with, but I found that the easiest way to do change the TTL’s for everyone on one server is with a simple replace:

replace 86400 3200 — /var/named/*.db

You can change the first value to whatever you have your default TTL set to, which is indicated in /etc/wwwacct.conf. After this, use the following script to increment up the serial numbers:

http://www.ndchost.com/cpanel-whm/scripts/updateserial/

Now sync the zones out to the cluster to update your nameservers:

/scripts/dnscluster synczone all

Add the new IP

A couple days after you make this change, add the new IP to your server. You can edit /etc/wwwacct.conf to indicate the interface and IP that should be shared, but I find that having the main IP also be the shared IP works best. The reason for this is that if you, for example, have the eth0:1 interface as the shared IP, each IP added after that as an alias will have an interface of eth0:1:x and won’t work properly.

To change the main IP of the server:

Edit /etc/sysconfig/network-scripts/ifcfg-ethx (ethx = adapter your public IP is on)
Modify IPADDR, NETMASK, GATEWAY and NETWORK to match your IP parameters (some may not be present)
Edit /etc/sysconfig/network to change additional parameters not preset in the previous file
Restart the network service
NOTE: This example refers to a Redhat-type system. Actual file names you need to edit would differ depending on what flavor of Linux you’re on.

Update configurations

Now, all you need to do is run a few more replace commands:

➨ replace $oldip $newip — /var/cpanel/mainip
➨ replace $oldip $newip — /var/cpanel/userdata/*/*
➨ replace $oldip $newip — /var/named/*.db
➨ replace $oldip $newip — /etc/*
➨ service named restart
➨ /scripts/rebuildhttpdconf
You also need to run the same script as before to update the zone serials again (now that they have new IPs) and sync the domains back up to the clusters. Then use the same replace command (only opposite) to change the TTL’s back to the original values.

To complete the change, I would advise running a cPanel update in case any internal cPanel files are using the previous IP.

Monday, 5 December 2016

What is cloud hosting?

Cloud hosting is a hosting solution which works on cloud computing technology wherein services like storage, compute, network, servers, and applications are provided to organizations via a network like internet.

This form of hosting enables companies to consume compute resources as a utility, like electricity, thereby eliminating the need of building and maintaining computing infrastructure in-house.

Benefits delivered by cloud hosting solution:

1. Pay for the resources that you use- Cloud hosting is a low- cost hosting platform as customers are billed only for the resources which they procure. Moreover it saves their upgradation costs too by helping them make most of their current IT infrastructure.

2. Instatenous allocation of resources- This hosting set up facilitates on-demand scalability. It allows websites and business to add or reduce resources (bandwidth, storage, RAM etc.) as per their business needs.


What is Cloud Hosting? How does it really work?
3. Increased team collaboration and productivity- It enables employees of an organization to work on the same document by sharing files, applications and other documents online, irrespective of the location they are working from. Thus, enabling flexible and smart working in the work place.

4. Independence of location- A business hosted on cloud platform is globally accessible as cloud servers are present across the world. They are accessible from anywhere via an internet connection and with any device-desktop, laptop or even mobile.

5. No single point of failure- Cloud hosting promises ‘five nine’ network uptime as it is a system of inter- connected servers. So whenever a single server or a component is unable to take the client’s request, then the other one out of the multiple servers takes over the workload of the failed server by default.

6. Backup and disaster recovery- Data is automatically backed up in cloud connected servers.

How it really works?

What is Cloud Hosting? How does it really work?

Cloud mainly consists of two components:

⟾ Front end – Refers to the client part of cloud computing. Comprises of interfaces and applications, required to access the cloud. 

It is similar to the Facebook profile which you use to interact with people.

⟾ Back end – Refers to cloud itself. Comprises of virtual machines, servers, data storage, security mechanism etc. Its control remains with hosting provider. It delivers the data which we see in the front end.
Other sub-components are cloud based delivery and network-like internet.

Cloud computing works on the virtualization technology. It partitions a single physical server into multiple servers and once the server is divided, each server acts like a physical server and is capable of running an operating system and applications independently.

There are three cloud deployment models -

1. Public cloud- Resources are provided by cloud provider to public via internet.
2. Private cloud- Resources and infrastructure are dedicated for the use of a single organization.
3. Hybrid Cloud- This model combines goodness of public cloud with private cloud, thus delivering best cloud environment.

Cloud is a wide network and so is a vast topic too. I’ve shared only the basics, to keep it short and sweet. If you have any doubt on cloud hosting service or looking for cloud hosting providers you can check it here.

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