Hibernation was designed for laptops and might not be available for all PCs. It uses less power than sleep and when you start up the PC again, you're back to where you left off. Hibernation suspends to disk unlike the sleep option that suspends to RAM. That's why it takes a bit longer to wake up from hibernation than from sleep.
PNG is short for Portable Network Graphic, a type of image file. It’s particularly popular file type with web designers and widely used on websites to display high-quality digital images because it can handle graphics with transparent or semi-transparent backgrounds. PNG files, which use the .png extension, can handle 16 million colors - which definitely sets them apart from most file types.
Docker is a service that use OS-level virtualization to deliver software in packages called containers. Containers are isolated from one another and bundle their own software, libraries and configuration files; they can communicate with each other through well-defined channels. Because all of the containers share the services of a single operating system kernel, they use fewer resources than virtual machines.
Cron is a time-based job that runs in the background at specific intervals or designated times. It allows you to run tasks and scripts automatically, making cron useful for automating maintenance-related tasks. Therefore, it is a very popular server administration tool.
Cron is present in all Linux distributions. However, if it is not installed, you can install it using apt:
Nginx is open source software for web serving, reverse proxying, caching, load balancing, media streaming, and more. It started out as a web server designed for maximum performance and stability. In addition to its HTTP server capabilities, Nginx can also function as a proxy server for email (IMAP, POP3, and SMTP) and a reverse proxy and load balancer for HTTP, TCP, and UDP servers.
Swap space is the area on a hard disk. It holds memory pages that are temporarily inactive. Swap space is used when your operating system decides that it needs physical memory for active processes and the amount of unused physical memory is insufficient. When this happens, inactive pages from the physical memory are then moved into the swap space, freeing up that physical memory for other uses.
In Bash and other Linux shells, when a program is executed, it uses three standard I/O streams. Each stream is represented by a numeric file descriptor: