In Nublue Blog

What is CloudLinux?

Stefan Posted by

CloudLinux OS logo

CloudLinux is a Linux-based operating system for shared hosting, first released in 2010. It creates a wall around individual tenants hosted on the same shared server, which prevents these tenants from exceeding their resources or having a negative impact on other tenants’ website performance as a result.

It’s derived from Red Hat Enterprise Linux, which it modifies and extends specifically for use with shared hosting environments. CloudLinux provides its own kernel (the core ‘middle man’ between applications and hardware data processes) based on the OpenVZ kernel, plus a number of supporting packages which implement and support the resource isolation it provides. Memory, CPU and a number of web server connections can all be manipulated within CloudLinux.

What does CloudLinux let us do?

CloudLinux helps to make sure our shared servers are stable, and that our shared hosting clients are protected against slowdown, downtime and resource spikes which could be caused by other clients sharing the same server.

It lets us partition resources in our shared servers, so that a resource-hungry website can’t slow down or crash other websites on the same server. CloudLinux gives us close control of our shared servers’ resources to ensure we provide the best performance for all our shared hosting clients. Any client website which uses more than its allotted resource limit is kept isolated and their resource usage is ‘throttled’ by CloudLinux, which prevents any knock-on effects of this data overage for other users on the same server.

Without a service like CloudLinux, having multiple tenant websites on a single shared server could result in site slowdown or even crashes, if one website uses more than its agreed resources on the server. CloudLinux helps to ensure that our shared hosting remains stable and performing at its best for our clients.

Essentially, CloudLinux lets you enjoy your shared hosting secure in the knowledge that one (or more) greedy websites you share a server with can’t impact your own site’s performance. It means that if a particular website expends its resources it will begin to slow down, and stop working until its level of resource usage reduces to within its limits. If this happens regularly with a particular client then we will contact them to advise them on a new hosting package with more suitable resource for their website. However, all other clients on the same shared server will be unaffected by the stoppage and will run as usual.

CloudLinux also walls off each user in their own virtualised file system using CageFS and SecureLinks, so that even if a client is hacked, the hacker will be unable to see any other user on the same shared server – or their sensitive information.

When do Nublue use CloudLinux?

We’ve used CloudLinux on our shared hosting platform since 2012, and we and our clients have benefitted from the stability and performance it provides. We also offer CloudLinux as an add-on for our dedicated servers, and we strongly recommend its use where clients are reselling hosting to others, as a means of protecting their individual clients from the resource usage of others on the same shared servers.

We also have some customers who use CloudLinux as an additional protection, to prevent their development work impacting their live sites where they are sharing the same server.

The CloudLinux OS is also especially useful for our clients running websites on the WordPress and Joomla platforms, since its OptimumCache feature can optimise file caching by removing the need to read duplicate site files.

Without CloudLinux we wouldn’t have the same high degree of control over client websites’ resource usage on our shared servers. For example, we’d be unable to set specific limits for CPU and RAM usage by our shared clients, and it could take a long time to pinpoint problematic accounts causing issues over resource usage on a shared server which hosts many clients.

Additional notable features with CloudLinux

  • CloudLinux provides control panel integration with Plesk, allowing historical graphing of resource usage for each shared hosting client
  • Its Mod_Isapi feature serves PHP quickly and more reliably by using less memory. Its MySQL Governor feature allows our system admins to monitor and manage MySQL usage in real time, and limits overages to stop overactive websites from overloading a whole server.
  • CloudLinux is based on the OpenVZ kernel, but also includes a range of additional functions. Notably these functions include a separate Lightweight Virtual Environment, with its own memory, CPU, IO and IOPS.
  • CloudLinux also provides HardenedPHP in multiple versions, which patches vulnerabilities in older versions and makes unsupported versions secure.
  • The cldeploy script is used to switch hosted clients to the CloudLinux OS. This installs the CloudLinux kernel and some lightweight virtual environment packages.
  • CloudLinux is often preferred for the high level of stability it provides with shared hosting, isolating each tenant on a shared server into a lightweight virtualised environment (LVE).
  • This LVE shares out and walls off memory, CPU and connections for each client on a shared server, and prevents any one client using more than their allocated resources. If a hosted website on a shared server sees a spike in traffic, or starts to use a lot of memory or CPU, only that individual LVE will be slowed down by the resource drain – not the entire server – preventing the server from going down. The result is faster, higher-performance hosting for all of our shared clients.
  • CloudLinux cites significant improvements in performance on servers using their OS, including a threefold drop in server reboots, a sixfold reduction in customer suspensions and 70% fewer tickets for issues related with server performance – as well as 20-30% reductions in server load.

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