The Virtual hosts are used to host the MULTIPLE domains on a SINGLE apache instance. We can have one virtual host for each IP your server has, or the same IP Address but different ports, or the same IP Address, the same port but different hostnames. The latter is called "the name-based vhosts".

In IP-based virtual hosting, we can run more than one web site on the same server machine, but each web site has its own IP Add while In Name-based virtual hosting, we can host multiple websites on the same IP address. But for this to succeed, we have to put more than one DNS record for your IP address in the DNS database. In the production shared web hosting ENVIRONMENT, getting the dedicated IP address for every domain hosted on the server is not feasible in terms of the cost. Most of the CUSTOMERS won't be able to afford the cost of having a dedicated IP Add. Here is the place where the concepts of the Name-based virtual hosting find its place.

How the system administrator can manage and monitor memory USAGE in Linux?

Memory monitoring and usage management are one of the critical system administrator requirement. It’s always required to keep the system under monitoring to check if memory is low or any user or process is over-consuming it. Linux comes up with multiple commands that you can use to monitor and manage the usage. Different ways to check memory usage:-

Free: Free command gives details of memory used, free, cache and total. By default values are in KB but you can pass -m to have values in MB.

/proc/meminfo: This is a system file to monitor memory. It will give you 6 entries Total Active RAM, Total Inactive RAM, User Active RAM, User Inactive RAM, File Active RAM & File Inactive RAM.

Vmstat: VMSTATS give you memory statistics.

Top: Top command gives you memory usage and total RAM. This command also used for monitoring.