[CentOS] UBC primary parameters

UBC Primary parameters


This is the maximum number of processes and kernel-level threads allowed for a specific container

Many applications such as Apache, FTP and mail servers spawn a process to handle each client, so the limit on the number of processes defines how many clients the application will be able to handle in parallel. This does not limit how "heavy" the application is and whether the server will be able to serve those heavy requests.

The total number of processes on a system is restricted, once you have reached around 16,000 processes it will start to cause poor responsiveness of the system, worsening when the number grows. When the total number of system processes has reached or has exceeded 32,000 it is very likely to cause the system to 'hang' or 'stop'


This is the maximum number of TCP sockets

This parameter limits the number of TCP connection and as such the number of clients the server application can handle in parallel.


This is the maximum number of non-TCP sockets (local, UDP and other types)

Local (UNIX-domain) sockets are used for communications inside the system. Multi-tier applications (for example, a Web application with a database server as a back-end) may need one or multiple local sockets to serve each client. Most mail servers do not use local sockets

UDP sockets are used for Domain Name Service (DNS) queries, SMTP agents may also use UDP sockets.

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