Linux Tips • Page 80 of 114 • Getting you up to speed!

Monitor TCP/UDP In Real Time

If you’re concerned about network connections to your device, you may want to monitor TCP/UDP in real time. It’s a pretty handy way to get a handle on what connections are being made by your devices. This article could be pretty complicated, but I’ll try to make sense of it all.

By the way, if you ever want to be sure you know something, try explaining it to someone who knows nothing about it. It can be pretty humbling. Leave a comment letting me know how I did.

Anyhow, moving on…

Network connections happen on various ports. Think of them as though your computer is a country and you have various ports that let traffic in and let traffic out.

There are different kinds of traffic, just like there are different kinds of ships. You have leisure, goods, military ships, etc… You have cruise ships, tankers, cargo yachts, kayaks, aircraft carriers, etc. Traffic is often bidirectional, meaning going in and leaving on the same port. In the case of TCP and UDP, traffic is bidirectional so one port will accommodate both.

So…

What Are TCP and UDP Anyhow?

In the case of TCP, you may be familiar with the expression TCP/IP, and it stands for Transmission Control Protocol. TCP requires a server/client relationship and should only be used on certain ports. Those ports are things like FTP, SSH, SMTP, Time, TELNET, etc… So, if you know you don’t have an FTP server running, you really shouldn’t be seeing traffic on ports 20 or 21.

UDP, on the other hand, stands for “User Datagram Protocol”. Unlike UDP, there’s no client/server relationship required. It just spews traffic out as needed/ordered. UDP connections do things like check a DNS server to find the IP address for a domain name. It then waits for the server to respond. There’s less latency and it’s more useful for ‘real time’ processes. Voice and video may be sent using UDP. Again, if you’re seeing unrecognized traffic, there may be a problem.

If you want, you can get a general idea (you don’t really need to memorize this) of what belongs where, with regards of TCP/UDP traffic. Wikipedia has an excellent list of TCP/UDP port numbers.

So, with that information at hand, you can see why you might want to …

Monitor TCP/UDP In Real Time:

This article requires an open terminal, like many other articles on this site. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

Once you have your terminal open, you can use ‘netstat’ and examine this in detail. If you just want to check once, you can run this command:

sudo netstat -tulpn

1	sudo netstat -tulpn

To monitor it in real time, you’ll just use the ‘watch’ command. That’d look like this:

sudo watch netstat -tulpn

1	sudo watch netstat -tulpn

You can use the -n flag to change the refresh interval, as it will default to every two seconds. To make it every five seconds, the command would look like this:

sudo watch -n 5 netstat -tulpn

1	sudo watch -n 5 netstat -tulpn

You can change that number, but you can go no lower than once ever 0.1 seconds. I’m not sure if there’s an upper threshold, but it might have one.

Either way, you can monitor your TCP/IP connections in real time. It’s not really all that difficult. You may see some results that alarm you, but odds are you’re just new to checking the output. Before getting alarmed and making drastic changes to your computer, research to see if the connection is actually just normal traffic.

Closure:

And there you have it, you have another article to read. This one is about how you can monitor TCP/UDP in real time, a useful tool if you’re concerned with your network’s traffic. Malicious activities will likely require network ingress and egress, so this can help your security assessments. Strange connections don’t necessarily mean there’s a problem – but they do mean you might want to look to see what’s causing the connections.

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Remove Default Music Player In Elementary OS

It can be a little confusing if you want to remove the default music player in Elementary OS. It isn’t really all that clear immediately, so here’s an article explaining how to remove the default music player in Elementary OS.

The default music player in Elementary OS (eOS from here out) is kinda lame. There are many better choices out there. Once you’ve chosen a replacement music player, this is how you remove the default music player in eOS.

This was first asked on a forum that I frequent and I took the time to find the answer. I figured that I’d not been able to easily find the answer with a search engine, so I might as well turn it into an article. It’s actually pretty simple.

eOS lacks any handy GUI system monitor that I could find, so I installed one. You might as well do the same. With eOS, you’re eventually going to want it – though top or htop or even atop do the job just as well.

Anyhow, I installed one and found that closing the “io.elementary.music” process closed the music player. Obviously, you can’t uninstall that. It’s part of some bigger package and eOS does things in unusual ways.

With further digging, I finally noticed an application called ‘noise’ in the list of running processes. Killing it would kill the music player, just like killing the io.elementary.music process would. Finding this out pleased me, as that was the answer.

Remove Default Music Player:

With that information in hand and properly tested, I was able to give the answer. The answer began with telling them to open their terminal, which you can do easily enough. Just press CTRL + ALT + T and your default terminal should open.

With the terminal open, it’s just one single command:

sudo apt remove noise

1	sudo apt remove noise

It’s so intertwined with eOS that you might want to reboot after you’re done. You can do that with the following command:

sudo reboot

1	sudo reboot

And there you have it. That’s all you need to do. I’m not sure why eOS makes it so difficult to find this. I’m also not sure why it wasn’t widely published, but it’s online now. Technically, it was online before now -at my old site. This is actually an old article that was redone to suit this site.

Closure:

We are getting closer to the one year mark. It’s less than a month away. I’m probably going to take a day or two off and then get back to the regular schedule – though with maybe a little less pressure to get it done every other day. It’s great when I have a half dozen articles done and ready to publish, but not so much when I’ve run out of ideas and I need an article for tomorrow. Ah well…

Change Your DNS Servers To Google’s In Lubuntu

This article will show you how to change your DNS servers from your default servers to the DNS servers run by Google, specifically while you’re using Lubuntu. If you’re not using Lubuntu, the process is likely fairly similar. Either way, it should be a nice and fun article, and we’ll even do it in the GUI instead of the terminal.

So, what is DNS? DNS stands for ‘Domain Name System’. As you know by now, machines are identified by their IP address. It’d suck to have to remember numbers instead of names. It’s also possible to route multiple domain names to the same IP address. So, we have domain names and use those domain names to resolve to IP addresses.

If you’re like most people, right now the DNS servers you’re using have come from your ISP – the folks who provide your internet service. This means that they can see which sites you visit, based on the requests you make to the DNS service.

Some folks don’t like this and prefer to find another DNS provider. (There’s also Secure DNS which this article will not be touching on.) One of those companies that provides free DNS servers is Google. Like them or not, their DNS servers are robust and consistently updated, often making domain propagation quicker for you.

This article is for Lubuntu, as stated above, but you may very well be able to follow the same exact steps with your distro of choice. And, now that you have a general idea of what’s going on, let’s learn how to…

Change Your DNS Servers:

To get started with changing your DNS servers, you need to find your networking icon in your system tray. It’ll be down on the right, not far from the clock. Once you have found it, right click on it so that it brings up the menu to let you “Edit Connections”. It will look something like this:

change network settings — Of course, your version won’t have the nifty arrow.

You’ll want to click the gear icon. That’s why I put the arrow there!

That will open another window. This window will have tabs you need to worry about – or a tab you need to know about. You probably shouldn’t need both. The tabs you’re interested in will look like this:

changing the network connections — You should need one of those, probably not both of those…

Now, you should only need to edit one of those. If you’re still using IPv4 then you use that tab. If you’re using IPv6 then you’ll obviously want to use the appropriate tab. For example, the IPv4 would look like this:

screen to edit dns servers — This would be the tab you’re looking for, pretty much…

Now, where that arrow is is where you want to enter the new DNS server information. You separate them with a comma, though you can use a comma and a space – there will need to be a comma.

For Google’s IPv4 addresses, your choices for 8.8.8.8 and 8.8.4.4.

For Google’s IPv6 addresses, your choices are 2001:4860:4860::8888 and 2001:4860:4860::8844.

Note: The ifconfig or ip addr will help you tell if you have IPv4 or IPv6.

When you’re done, be sure to click the save button to ensure your new settings take effect. Remember the screen and changes, should things go pear shaped. You can undo this easily enough.

This will, of course, work with any set of DNS servers out there. You can use it with other servers if you aren’t a fan of Google. This can serve as a general guideline for other servers, should you wish.

Closure:

Yup… There it is. You have another article. This time, it tells you how to change your DNS servers if you use Lubuntu. Again, it’ll work for other distros, but I’m only including pictures/vouching for it with Lubuntu.

How To: Clear The Terminal Screen

Today, we’re going to learn to clear the terminal screen. This is generally done for privacy’s sake. You don’t want people to be able to scroll up and see what you’ve been reading in the terminal. This probably isn’t as important if you’re the only user and you’re in your house, but you may still like to keep things clean and tidy.

We’ll go ahead and cover two ways to clear the terminal in this article. They’re both rather easy commands and you’ll find this article is definitely not all that complicated, or even very long. This is pretty much one of the first things folks should have learned when they started using the terminal. We might as well cover it here.

Rather than make this long-winded, we’ll just make this into a short and easy article to read. Let’s all learn how to…

Clear The Terminal:

To be clear, this just erases the text in the terminal. It clears the scrollback content so that folks can’t scroll up and see the previous terminal contents. Again, it’s a good idea to do if you’re in a multi-user environment where people may have access to your screen and you don’t want them to know what has been written to the terminal.

Obviously, you need a terminal for this article. Just press CTRL + ALT + T and your default terminal should open.

I suppose we’ll need some content, so let’s try using this command:

ls -la

ls -la

That should fill your terminal up.

Now, to clear it you can use either of the two following commands:

clear

clear

Or you can also use:

reset

reset

(Though reset may leave a little text at the top, it still removes the terminal’s scrollback history.)

Both of those will do the job, with ‘clear’ being the obvious winner = but it’s nice to have options. They’ll clear the scrollback in the terminal, preventing folks from scrolling up to read what has previously been written there. Of course, they could potentially still press the arrow up button and see what commands you’ve written, so you can try to prevent that as well.

Closure:

See? I told you that it’d be a quick and easy article. It’s not all that taxing to learn how to clear your terminal and that’s all that this article is meant to cover. Both of the two commands have a man page, but they’re not very useful commands for anything else but clearing the terminal. Have an easy day, a day where you can (maybe) say you learned something and not have to read a long article. After all, it was a quick and easy day for me!

It’s Time To Introduce You To The Terminator!

Today’s article is about one of my favorite terminal emulators, Terminator. Terminator is one of my favorite terminal emulators, and I’d like to use this opportunity to expose more users to it. For lack of a better category, we’ll say this is a review. Why not? It’s my site, I’ll call it a review if I wanna! I’ll make it a review!

So, we call it a terminal emulator because it emulates the terminals of old, back when terminals were the main way for a person to interface with their computer. They are not true terminals, but they perform similar functions. Long gone are the days of just green-screens. Today, we have graphical user environments and there’s less focus on the terminal for some folks. From here on out, I’ll just be calling it ‘terminal’ for simplicity and brevity sake.

There are some die-hard folks who still cling to the terminal – and I’m one of them, at least for certain tasks. At any given moment, I have at least two terminal instances open, each a different piece of software. One of those is usually Xfce4 and the other is often Terminator. Today’s article is about the latter.

Chances are good that you can install Terminator with ease. It’s likely in your default repositories. For example, on Ubuntu you’d install it with this command:

sudo apt install terminator

1	sudo apt install terminator

Go ahead, give it a shot… If not immediately available, you can look here for more information. If you’re really energetic, you can read the documentation. In this case, it’s going to be a positive review (obviously), so I’d not recommend it (such as I am) if I wasn’t a fan… So…

Why Terminator:

You’ll not be even remotely surprised when you open Terminator for the first time, and that’s a good thing. You’ll see your standard terminal looking thing, complete with a title bar. Truthfully, it’s kinda ugly looking until you make it your own (more on that in a minute). It looks like this:

terminator terminal emulator in its naked form — Terminal (terminal emulator) without any customizations.

What you’re looking for is in the right mouse-button click – the preferences menu. Once you open that, you’ll see all sorts of options.

Once in the options, you’ll start to understand why I like Terminator. You can make it visually appealing, use multiple tabs, group tabs, auto-run commands when opened, and have all the various profiles you could possibly want. If you’re working on multiple servers at the same time, this is definitely a great help.

You have infinite theme options, but there are a number of them that are built in – the standard types like solarized dark or light. If I’m not taking screenshots, I like mine to look like this:

terminator with a thene — As I’m often in a dark room, this is excellent for my eyes.

That is so much nicer on my eyes. And, if the Terminator theme didn’t clue you in, yes I am using a computer that I don’t normally use. It’s a long story, but nothing is broken beyond my ‘net connection. But, that’s why the screenshots look different. I am also using Flameshot instead of my beloved Shutter.

So, that’s not enough? Seriously – go through and check the preferences. You have global options and then you have all sorts of preferences that you can pick – each contained in their own distinct profiles. When you get to the profiles, you’ll see how much customization is really possible. Allow me to show you:

terminator has options - lots of them — As you can see, there are a whole lot of options with Terminator.

What does Terminator offer? A whole lot… Not only are there tabs, you can set it up in a more traditional grid fashion. These layouts can be moved with drag-and-drop. The list of keyboard shortcuts is extensive – and you can probable tell I’m just reciting the documentation. Layouts are even saved from session to session.

But Wait, there’s more!

Anyhow, all those preferences, not just layouts, can be saved from session to session. Once you get it configured the way you want, it’ll let you retain those settings. Many of these are all extensions of the profiles feature, so it’s highly customized if you want it to be.

I especially like the individual profiles – not seen on this computer’s screenshot. If I paid a bit more attention, I could just copy the config from ~/.config/terminator, but I’m slacking and this situation is temporary. (I’m amazed that I’ve still been able to keep up my publication schedule!) I did not, so you get a different set of screenshots.

If you want, you can even find plugins for Terminator. You can write your own, if such is your desire. If you click here, you’ll see a bunch of plugins that you can use to extend Terminator even further. (Quite a few plugins exist, so do check the link.)

Note: I also wrote an article explaining how to change your default terminal.

As I said, there are quite a few plugins and some of them are quite useful – especially for system admins and programmers, or DevOps folks I guess. They’re universally free, in every sense of the word. They’re also easy to install – just drop them into ~/.config/terminator/plugins/ and they’ll be available to enable from the preferences menu.

If nothing else, go ahead and install Terminator to see if you like it. I dare say that you won’t be disappointed, unless you’ve got some weird edge-case and even then it’s about the best you’re going to get.

Rating Terminator:

Terminator does everything you can want in a terminal, more or less. If it doesn’t do what you want, plugins are easily developed and someone else may have scratched that itch for you already.

I honestly can’t think of anything it’s missing that I personally need or want. It can be a bit boxy and the look is dated, but it should match your theme fairly well, or better if you do some work customizing it.

I appreciate how easy it is to configure it to work with my eyesight. I’m partially colorblind (not the way you’re probably thinking) and have difficulties with the spaces between the primary colors. I can see green, but yellow-green may appear as either yellow or green to me. So, some of the themes (again, you can customize them as much as you desire) are wonderful for my eyes.

Yeah, try as I might, I just can’t think of anything bad to say about it. I’m reluctant to give anything a 10/10, but this is really close to being the perfect application for the task it is designed for. I’d even go so far as saying that it’s feature-complete, but some folks must not agree ’cause they keep writing plugins and that means they want more features.

So, I’m going to give this a 9.5 out of 10. That’s the highest I’ve ever rated anything on this site and I’d not expect to see that score for anything else. I knock the 0.5 because obviously people expect more from it – options they feel should be defaults. A few of the plugins are indeed handy (even to me, a simplistic user). Yeah, I’ll knock off the points for that. That sounds good. It gets a 9.5/10. That’s pretty much a gold medal winner, right there!

Closure:

And there you have it… You have another article – this one a review, and a review of not just one of my favorite pieces of software but of a piece of software I use many, many times a day. Even if you have a favorite terminal, give Terminator a try. You won’t be disappointed – probably… If you are, you’re just weird!