WebHost Manager (WHM) is described as 'WHM gives you a lot more control and flexibility when managing either a few very popular and resource-intensive sites or a large number of sites' and is an app in the Network & Admin category. There are three alternatives to WebHost Manager (WHM) for Linux, Online / Web-based, Self-Hosted solutions and BSD. The best alternative is Virtualmin. It's not free, so if you're looking for a free alternative, you could try CentOS Web Panel.
CentOS Web Panel - Web control panel is designed for quick and easy management of (Dedicated & VPS) servers without of need to use ssh console for every little thing. There is lot's of options and features for server management in this control panel.
DirectAdmin is the easiest to use control panel. DirectAdmin is programmed to be the fastest running control panel available. DirectAdmin avoids downtime by automatically recovering from crashes. We offer lightning-fast support by phone, e-mail, forum, and live online chat.