The difference among VIRT, RES, and SHR in top output LinuxAdd comments VIRT stands for the virtual size of a process, which is the sum of memory it is actually using, memory it has mapped into itself (for instance the... Continue Reading →

Memory in Linux

FROM: One basic concept in the Linux implementation of virtual memory is the concept of a page. A page is a 4Kb area of memory and is the basic unit of memory with which both the kernel and the CPU... Continue Reading →

POJO (plain old Java object)

From Wikipedia In software engineering, a plain old Java object (POJO) is an ordinary Java object, not bound by any special restriction and not requiring any class path. The term was coined by Martin Fowler, Rebecca Parsons and Josh MacKenzie... Continue Reading →

less -R

PTR record

You can think of the PTR record as an opposite of the A record. While the A record points a domain name to an IP address, the PTR record resolves the IP address to a domain/hostname. PTR records are used... Continue Reading →

file permissions

The @ is displayed with a extended attribute is set The + is displayed for an ACL. IF you have both an attribute and a ACL then you see @. Run the command ls -le filename to see if it... Continue Reading →


Prefork VS Worker MPM

Prefork and worker are two type of MPM apache provides. Both have their merits and demerits. By default mpm is prefork which is thread safe. Prefork MPM uses multiple child processes with one thread each and each process handles one... Continue Reading →

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