How to Uninstall Software in Ubuntu 18.04

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Introduction

In this tutorial, we will demonstrate how to quickly and easily uninstall software from Ubuntu. Uninstalling software can be done using several techniques. In this article, we will show you how to uninstall software using these various methods.

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How to Install and Correct Dependencies Issues in Ubuntu

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What is a Dependency?

A dependency is defined as a file, component, or software package that a program needs to work correctly. Almost every software package we install depends on another piece of code or software to work as expected. Because the overall theme of Linux has always been to have a program do one specific thing, and do it well, many software titles utilize other pieces of software to run correctly.

Introduction

Let’s review what dependencies are and why they are required. We all have, at one point or another, most certainly seen a message from our system when we were installing software regarding “missing dependencies.” This error denotes that a required part of the software package is outdated, unavailable or missing. Let’s review how to address those issues when we come across them on Ubuntu.

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How to Install and Use ApacheTop

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What is ApacheTop?

ApacheTop is an uncomplicated command line (CLI) utility that is used to monitor http traffic in real-time. It achieves this task by analyzing the incoming apache logs and based on that data presents understandable output to our screen. It can be configured to output X number of hits, or output X number of hits within X seconds.

Introduction to ApacheTop

Website owners and administrators oftentimes find themselves interested in the traffic for a specific website or multiple websites on the server. They might need this information in order to troubleshoot a high load issue on the server, or simply to learn the traffic pattern of a website, which is crucial for running a business. This information is logged in the web server’s access logs, and we can look through them to learn about the website’s traffic that has occurred in the past. Parsing through these logs to make most sense of them requires some basic skills in Bash, though, so it is not always very convenient.

However, we might want to learn more about the traffic in real-time in cases of currently high load on the server or issues with a website. In this case, we can use a monitoring tool called ApacheTop, which shows traffic in real-time. Furthermore, it collects the information from the web server’s access log and parses through it so that it generates human-readable output. This way, we can see what pages are being seen on the server in real-time, but we also do not need any Bash skills to parse through the output. It displays the information such as requests per second, bytes per second and URLs that are being requested, and its display is modelled after the standard top utility.

ApacheTop keeps a table of information by containing all the relevant data about the requests it has collected, but it can only be of a certain finite size. By default, it will show the data within the 30-second time frame, but we can define its size in a couple of ways. This can be done by making it remember a certain number of hits, or a certain number of seconds, after which it resets. We should also note that ApacheTop tool uses Apache’s default access log file for the traffic information, however, in case of a custom log path, we can also specify which log file to look through.

Installation

We can install ApacheTop like any other package, but we need to have the EPEL repository installed first.

CentOS Based Systems

yum install epel-release
yum install apachetop

Debian Based Systems

On Debian/Ubuntu based systems, we can use apt-get to install apachetop

apt-get install apachetop

Using ApacheTop

In order to use ApacheTop, we can simply run the command apachetop from the command line. This will, without specifying anything else, by default use the Apache access log and display information within a 30-second timeframe.

Flags

If we want to use a custom log path, we can specify it with the -f flag:

apachetop -f /path/to/the/log/file

In order to change the default 30 second time range for showing data, we can do so with one of the following flags:

  • H – This flag specifies the number of hits we want ApacheTop to display. The following example will show the last 100 hits
    apachetop -H 100 
  • T – This flag specifies the number of seconds for how long ApacheTop will keep track of the data. In the following example, ApacheTop will be showing hits in the last 60 seconds:
    apachetop -T 60

Some of the additional flags that we can also use include the following.

  • – q – This flag instructs ApacheTop to keep the query strings, instead of removing them
  • – l – This flag instructs ApacheTop to use all lowercase URLs, which causes it to accumulate the same statistics for both uppercase and lowercase URL
  • – s segments: This flag instructs ApacheTop to keep only the first parts of the path, which causes the statistics to be merged for each truncated URL
  • – p – protocol: This flag is kept at the front of its referrer strings. By default, it is removed to give more room to more useful information
  • – r secs: This flag sets the default refresh delay in seconds

Reading the Output

When we run the apachetop command, at the top of the screen we can see a summary of the statistics, as is shown in the image below. 

1 Last hit

The first line shows the time of the last hit, ApacheTop running time and the current time of the server.

The second and third lines show the statistics of all the visits since ApacheTop started running. On the second line we can see the total number of requests, along with the number of requests per second; total size of all requests with the number of bytes per second; and the average size of each request. The third line shows the number of requests that are returning 2xx, 3xx, 4xx and 5xx web server response codes.

The fourth and fifth lines show the same statistics as the second and the third respectively, but they only display the information within the specified, or default, time range.

Below these top five lines, we have the list of URLs that are being requested, with the total number of hits for each, and the size of the request in question, as can be seen in the image below.

2 URL List

The star (*) symbol next to the URL specifies which request is selected. We can select different requests by moving with the Up and Down arrow keys. Once we reach the request we are interested in, we can press the Right arrow key, which will take us to the page with details for that request. The details include the hosts requesting that URL and the referrers. To return to the main list, we can use the Left arrow key.

We can also switch the main view from showing the URLs, to show Hosts, or Referrers instead, by pressing the d key. In the image below, we are currently seeing the hosts instead of the URLs:

3 Hosts

Filters

We can also choose what to see in the view by using filters. We can access those by pressing the f key, and we will be presented with three options:

  • add
  • clear
  • show active

Pressing each of the letters will activate the corresponding action. If we want to add a filter, we would press the a key, and then we can choose if we want to filter by

  • url
  • referrer
  • hosts.

Pressing the corresponding key would let us enter which URL, or referrer or host we want to filter by. Once we enter the information, the view will only show the requests that fit the entered criteria.

Conclusion

The ApacheTop utility is an extremely useful monitoring tool that is easy to use while providing human-readable information that can help pinpoint the cause of certain server and website issues. However, one should keep in mind not to monitor the traffic with an extended time frame or too many hits, as that would use too many CPU and memory resources, which could only add to the problem at hand.

Installing Microsoft Powershell on Ubuntu 18.04

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If you are a Windows administrator who has recently been tasked with administering a Linux-based Ubuntu server, you may find that utilizing Microsoft Powershell may help ease the transition into Linux, and allow you to be more productive. If you are a Linux administrator who is interested in exploring the options that Powershell provides, then this tutorial is for you as well.

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How to Uninstall Software on Ubuntu

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In this article, we will be discussing the various methods and techniques used to locate and uninstall the software from a Ubuntu/Debian based server. We will primarily be using the apt and dpkg commands on the command line.

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How To Create A Software Install List

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Purpose

The purpose of this article is to describe and explore ways to copy or backup your currently existing installed software titles into a single file for later use. We can then use this file to reinstall the software onto another system or clone the existing software across multiple Linux systems on or across a network. This method also prevents the need to install software titles one by one.

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How To Install Software From Source on Ubuntu

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In this article, we are going to cover the available options for installing software on an Ubuntu Dedicated server. By the end of this article, you’ll be equipped with an arsenal of tools for installing the exact software you want on your Ubuntu server! We will be installing three different software packages from source, deb, and flatpack.

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