Systems

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:

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.

Rsync is a very flexible network-enabled syncing tool. Due to its ubiquity and its popularity as a tool for system scripts, it's included on most Linux distributions by default. It efficiently copies and sync files to or from a remote system. It’s faster than scp because rsync uses a remote-update protocol which allows transferring just the differences between two sets of files. The first time, it copies the whole content of a file or a directory from source to destination but from next time, it copies only the changed blocks and bytes to the destination.

MongoDB is a popular open source and document oriented database system. It belongs to a family of databases called NoSQL, which is different from the traditional table based SQL databases. It makes use of collections, each having multiple documents, and allows the user to store data in a non relational format. Data is stored in flexible, JSON-like documents where fields can vary from document to document. That's the reason for calling it schemaless database.

MongoDB is a popular open source and document oriented database system. It belongs to a family of databases called NoSQL, which is different from the traditional table based SQL databases. It makes use of collections, each having multiple documents, and allows the user to store data in a non relational format. Data is stored in flexible, JSON-like documents where fields can vary from document to document. That's the reason for calling it schemaless database.

Docker Compose is a tool for defining and running multi-container Docker applications. With Compose, you use a YAML file to configure your application’s services. Then, with a single command, you create and start all the services from your configuration.

The features of Docker Compose that make it effective are:

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:

Generally, OpenSSL is used for CSR generation on Linux-based web servers (Apache or Nginx) So, if the default web server is installed, there should be no issues with using OpenSSL as it is installed by default on these web servers.

The RSA key algorithm is the algorithm most widely used in digital security. It's an asymmetric cryptography algorithm. This basically means that there are two keys involved while communicating, i.e., the Public key and Private key.

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.

Docker provides the ability to package and run an application in a loosely isolated environment called a container. The isolation and security allow you to run many containers simultaneously on a given host. Containers are lightweight and contain everything needed to run the application, so you do not need to rely on what is currently installed on the host. You can easily share containers while you work, and be sure that everyone you share with gets the same container that works in the same way.