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PostgreSQL is an open source RDBMS (Relational DataBase Management System), and with any databases, the need may arise to scale and provide HA (High Availability). A single system providing a service is always a possible single point of failure - and even with virtual systems, there may be a time when you can't add more resources to a single machine to cope with the ever-increasing load. There also may be a need to another copy of the database contents that can be queried for long-running analytics, that are not fit to be run on the highly transaction-intensive production database. This copy could be a simple restore from the most recent backup on another machine, but the data would be outdated as soon as it is restored.

RPM, which stands for Red Hat Package Manager, is a well-known and mature package manager used by all Red Hat flavor distributions, as well as SuSE. With RPM the packager can define relations between packages, and even with versions of packages - for example, an Apache Tomcat server needs proper Java environment present to be able to run.

The objective is to install Tor on Ubuntu 18.04 Bionic Beaver. This guide will also provide you with some basic configuration and usage of Tor network in order to conceal your identity.

Packages to be installed with RPM package manager have the .rpm extension and are basically archives which contain the files provided by a library or an application plus information needed for the package to be installed and run correctly, such as its dependencies. In this tutorial we will learn how to use rpmrebuild, a very powerful tool which let us modify an existing rpm package without having to rebuild it from source code.

You many have heard of Owncloud. It was the primary solution for open source self hosted cloud storage for quite some time. Unfortunately, due to internal struggles, Owncloud split. Owncloud still remains, but it is currently owned by the people that caused the split. Nextcloud, on the other hand, is run by the original founder and the people who wanted to continue to work with the open source community.

Most likely, your are at the moment sitting in front of your computer, have a terminal window opened and wondering: "What should I do with this thing? Well, the terminal window in front of you contains shell, and shell allows you by use of commands to interact with your computer, hence retrieve or store data, process information and various other simple or even extremely complex tasks.

The objective is to create an offline digital and paper bitcoin wallet using Linux operating system, VirtualBox and Electrum Bitcoin wallet. The outcome of this tutorial will be a paper with written keywords which can be used to access your bitcoins. We will also create an encrypted version of virtual machine as a digital backup to be stored digitally on a secure medium which will provide a convenient access to your bitcoins if necessary.

During the administration of a system, being able to schedule a task for a later execution it's one crucial ability: to perform a backup of a database for example, or perhaps to run a maintenance script. Less known than cron or anacron, the at program let us do this in a pretty easy way: in this tutorial we will learn how to use it and how it is different from the programs mentioned above.

Lynis is a tool for performing an automated audit of your system. It's not a virus scanner or an antivirus. Instead, it checks certain criteria on your system to see how it's configured. By evaluating the system configuration, Lynis can give you an idea what areas are reasonably secure, and which ones need additional hardening.

It's important to regularly test any public-facing server to see which information it's making available. That information is important to attackers. They can use it to put together a picture of your server, what's running on it, and which exploits might work against it.

In a GNU/Linux system, while devices low level support is handled at the kernel level, the management of events related to them is managed in userspace by udev, and more precisely by the udevd daemon. Learning how to write rules to be applied on the occurring of those events can be really useful to modify the behavior of the system and adapt it to our needs.

The following article provides some useful tips on how to find all files within any specific directory or entire file-system containing any specific word or string.

Not everyone loves systemd, and for those that don't, there really aren't many options. That's especially true if you want something like a stable server. Fear not, SysV Init is actually still supported under Debian, and it's not hard to switch.

Firefox 57 is easily the best update to come to Firefox ever. Mozilla even named this release "Quantum" because of how dramatically the browser speed improved. Couple that with the complete redesign of Firefox's UI, and you have a pretty dramatic change.

If you have the good habit to never use the same password for more than one purpose, you have probably already felt the need for a password manager. There are many alternatives to choose from on linux, both proprietary (if you dare) and open source. If you, like me, think that simplicity it's the way to go, you may be interested in knowing however to use the pass utility.

Normally, on a unix-like operating system, the ownership of files and directories is based on the default uid (user-id) and gid (group-id) of the user who created them. The same thing happens when a process is launched: it runs with the effective user-id and group-id of the user who started it, and with the corresponding privileges. This behavior can be modified by using special permissions.

In a previous article we have seen how to parse command line arguments using getopts in the context of bash scripts (you can find the article here). Now we will see how to accomplish the same task, in a more powerful way, when writing a python script.

There are plenty of ways to play audio files with Python. It really depends on your application, but the easiest way, by far, is to use the bindings for VLC to control VLC with Python, and play your files. With VLC, you don't need to worry about codecs and file support. It also doesn't require too many complicated methods, and/or objects. So, for simple audio playback, VLC is best.

When writing scripts that are meant to run for a considerable time, it's very important to increase their robustness by making them able to react to system signals, executing specific actions when some of them are received. We can accomplish this task by using the bash trap builtin.

JSON is the universal format for passing data between programs and/or languages, especially on the web. Python has excellent built-in support for converting data from a Python program into JSON for another program to use.