Category Archives: Tutoriale Linux

Linux look Command Tutorial for Beginners (with Examples) | Linux.com


Although the Linux find command does a fabulous job for searching on the command line, there may be situations where a dedicated tool may be more convinient. One such case is to find lines in a file that start with a particular word. There exists a command – dubbed look – that does this for you.

In this tutorial, we will discuss this command using some easy to understand examples. But before we do that, it’s worth mentioning that all examples in the article have been tested on an Ubuntu 18.04 LTS machine.

Linux look command

The look command in Linux displays lines beginning with a given string. Following is its syntax:

look [-bdf] [-t termchar] string [file …]

And here’s what the man page says about the tool:

     The look utility displays any lines in file which contain string as a
     prefix.

     If file is not specified, the file /usr/share/dict/words is used, only
     alphanumeric characters are compared and the case of alphabetic charac?
     ters is ignored.

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Elementary OS Juno Brings Only Slight Changes to an Outstanding Platform | Linux.com


Elementary OS has been my distribution of choice for some time now. I find it a perfect blend of usability, elegance, and stability. Out of the box, Elementary doesn’t include a lot of apps, but it does offer plenty of style and all the apps you could want are an AppCenter away. And with the upcoming release, the numbering scheme changes. Named Juno, the next iteration will skip the .5 number and go directly to 5.0. Why? Because Elementary OS is far from a pre-release operating system and the development teams wanted to do away with any possible confusion.

Elementary, 0.4 (aka Loki) is about as stable a Linux operating system as I have ever used. And although Elementary OS 5.0 does promise to be a very natural evolution from .4, it is still very much in beta, but ready for testing. Because Juno is based on Ubuntu 18.04, it enjoys a rock-solid base, so the foundation of the OS will already be incredibly stable.

With that in mind, I downloaded 5.0 and spun it up in VirtualBox. The results are as impressive as I assumed they’d be. Let’s get this open source operating system installed and see what it has to offer.

Installation

I’m not going to spend much time on explaining the installation of Elementary OS. Why? If you’ve installed any flavor or Linux (or any operating system at all), then you can walk through the installation of this distribution in your sleep. There’s a rumor that Elementary OS is working in conjunction with System76 on a new installer. As of the current release of Juno, however, there is no sign of such an installer, so you’ll find the same method of installation seen in previous iterations of the platform.

You can run Elementary OS live or install it immediately. Burn the ISO image onto a CD/DVD or USB flash drive and boot it on your machine (or use the ISO image to create a virtual machine). The installer will have you configure your language, keyboard, select the installation type (Figure 1), select if you want to download updates immediately and install third-party media codecs, and then create a user.

Once the installation completes, reboot the machine and log in. Shortly after logging in, you should be prompted that updates are available. I highly recommend running the updates before using the desktop (since this is still in beta, the updates will come often). Now that we’re installed and updated, let’s take a look at some of those new features.

The AppCenter

The Elementary OS AppCenter has been given a slight facelift. Although the previous version was quite serviceable, it seems the designers have taken a nod from GNOME Software (which is a good thing) and added recommendations under the featured titles (Figure 2).

Another upcoming feature to the AppCenter is the ability to pay developers “what you want” for apps. The Elementary OS developers are taking a unique approach to apps. Elementary OS first released the AppCenter in May 2017 and by February 2018 they’d processed $1,700.00 worth of payments from just over 750 charges. That means the average paid price for an app, purchased from the AppCenter was $2.30. To make things a bit more lucrative for developers (and to try an interesting experiment), Elementary OS will include a HumbleButton for paid apps that allow users to pay what they will. Another change will be that paid apps won’t automatically update (if you click the Update All button in the AppCenter). Instead, to update the app, you’ll have to donate to the app (starting with $0.00 to $10.00 or a custom amount). Hopefully, that change will translate into more developers getting paid for their work.

Aesthetics

You won’t find too much in the way of aesthetic improvements in Juno. You’ll find no complaint here (as Elementary OS .4 Loki was already quite elegant). The designers did officially decide upon an official color palette. The full palette can be viewed here (along with all logo and font information).

Along with the new palette, Juno brings:

  • A Night Light feature (to make late night staring at the screen a bit less harsh on the eyes).

  • Latest GTK+ features (which includes some animated panel icons).

  • Very slight changes to the default theme (icons are a bit brighter and colorful).

App Changes

Because there are so few apps shipped out of the box, you won’t find much in the way of change here. The developers have rebranded the default text editor, Scratch, as Code and even rolled in some basic code editor features. Outside of that, the standard default Elementary apps remain intact:

  • Mail — for your email needs.

  • Music — to play your tunes.

  • Files — serves as your file manager.

  • Videos — plays all of your videos.

  • Calendar — schedule your day.

  • Photos — manage your photos.

Epiphany

At one point, I would have said having Epiphany as the default browser was a big miss. However, Epiphany has come a long way. Case in point: The version of Epiphany shipping with Juno includes the ability to log into your Firefox Account, so it can now sync and share data (Figure 3).

Another really nifty feature with newer releases of Epiphany is the ability to install a site as a Web Application. What this does is save a site as a launcher in the Elementary OS menu, such that you only need to click the launcher to open the site. When the site opens as an installed app, you will notice the browser window missing a few components (such as the bookmarks and configuration buttons, as well as the tab button/feature). It’s a handy way to gain quick access to specific sites you use frequently. 

To install a site as a web application, follow these steps:

  1. Open Epiphany.

  2. Navigate to the web site in question.

  3. Click the Epiphany menu button (gear icon in the upper right corner).

  4. Click Install Site as Web Application (Figure 4).

  5. In the resulting popup, give the application a name and click Create.

A bit of clean up and a conclusion

Outside of the above features (and a few more minor details), the rest of the change comes by way of old code cleanup and closing out issues. Thanks to that codebase cleanup, you’ll find a bit of a performance and stability increase over previous releases.

All in all, Elementary OS continues to be my top-rated distribution for new Linux users. It’s incredibly clean, elegant, and user-friendly. Thankfully, the design and development team understand they have something special on their hands and, instead of bringing about new features and radical changes, are set on offering only slight changes and improvements to an already rock solid Linux distribution. So, if you’re looking for something magical and radical in the shift from .4 to 5.0, you might be disappointed. If, however, what you want is nothing more than an improved (and very familiar) experience with Elementary OS, Juno will not disappoint.

Learn more about Linux through the free “Introduction to Linux” course from The Linux Foundation and edX.

ngrep – A Network Packet Analyzer for Linux | Linux.com


Ngrep (network grep) is a simple yet powerful network packet analyzer. It is a grep-like tool applied to the network layer – it matches traffic passing over a network interface. It allows you to specify an extended regular or hexadecimal expression to match against data payloads (the actual information or message in transmitted data, but not auto-generated metadata) of packets.

This tool works with various types of protocols, including IPv4/6, TCP, UDP, ICMPv4/6, IGMP as well as Raw on a number of interfaces. It operates in the same fashion as tcpdump packet sniffing tool.

The package ngrep is available to install from the default system repositories in mainstream Linux distributions using package management tool as shown.

$ sudo apt install ngrep
$ sudo yum install ngrep
$ sudo dnf install ngrep

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ctop – Top-like Interface for Monitoring Docker Containers | Linux.com


ctop is a free open source, simple and cross-platform top-like command-line tool for monitoring container metrics in real-time. It allows you to get an overview of metrics concerning CPU, memory, network, I/O for multiple containers and also supports inspection of a specific container.

At the time of writing this article, it ships with built-in support for Docker (default container connector) and runC; connectors for other container and cluster platforms will be added in future releases.

How to Install ctop in Linux Systems

Installing the latest release of ctop is as easy as running the following commands to download the binary for your Linux distribution and install it under /usr/local/bin/ctop and make it executable to run it.

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pdsh Parallel Shell | Linux.com


For HPC, one of the fundamentals is being able to run a command across a number of nodes in a cluster. A parallel shell is a simple but powerful tool that allows you to do so on designated (or all) nodes in the cluster, so you do not have to log in to each node and run the same command. This single tool has an infinite number of ways to be useful, but I like to use it when performing administrative tasks, such as:

  • discovering the status of the nodes in the cluster quickly,
  • checking the versions of particular software packages on each node,
  • checking the OS version on all nodes,
  • checking the kernel version on all nodes,
  • searching the system logs on each node (if you do not store them centrally),
  • examining the CPU usage on each node,
  • examining local I/O (if the nodes do any local I/O),
  • checking whether any nodes are swapping,
  • spot-monitoring the compute nodes, and
  • debugging.

This list is just the short version; the real list is extensive. Anything you want to do on a single node can be done on a large number of nodes using a parallel shell tool. However, for those that might be asking if they can use parallel shells on their 50,000-node clusters, the answer is that you can, but the time skew in the results will be large enough that the results might not be useful (which is a completely different subject). Parallel shells are more practical when used on a smaller number of nodes, on specific nodes (e.g., those associated with a specific job in a resource manager), or for gathering information that varies somewhat slowly. However, some techniques will allow you to run parallel commands on a large number of nodes.

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