Category: Networking

How To: Find Local Network Devices

Today’s article will be a bit of a weird one, as I share with you one way to find local network devices using the Linux terminal. I suppose network device discovery is typically seen as a dark art, something a malicious hacker might do, but it’s completely harmless (in and of itself). So, if you want to find local network devices, this article just might be for you!

What we’ll actually be doing is scanning a block of IP addresses to see what responds to our prodding. This is sometimes called IP Scanning or IP Sweeping. It’s also sometimes called Port Scanning, but we won’t be doing any real port scanning. I assure you, I am not secretly trying to turn you into a big bad hacker – but this is a pretty neat ‘hack’ (in the traditional sense of the word).

We will be learning just a single command (with a bit of explanation) with a single flag. It’s a very complicated tool and trying to cover it all would take a giant article or many smaller articles. You can guess which one we’re going to do!

The tool we’re going to use for this is called ‘nmap’. This is available in every major distro. It might be installed by default. It’s just the tool for the task at hand, so you need to install it before you can use it as this article will suggest. (I trust you to know how to do so at this point.)

Did you install nmap? If so, please continue. If not, read the last paragraph.

With nmap installed, you can check the man page to see that it’s described as:

nmap – Network exploration tool and security / port scanner

Now you’re ready…

Find Local Network Devices:

Picture this…

So, for some reason, one of my laptops has stopped answering on the .local domain when I want to connect to it with SSH. I have choices at this point. I could fire up Team Viewer and then connect to the laptop to find the IP address belonging to the said laptop. Another choice would be to get off my lazy butt and walk to the device, but that defeats the point of remotely controlling the device.

I suppose the best choice would be to just figure out why it’s stopped responding on the .local domain. Wouldn’t that be novel?

But, I have another tool! I have a tool that’s reasonably fast, very easy, and likely effective! That tool is, as suggested earlier, nmap.

The first thing I do is crack open a terminal to find my local IP address. That’s easy enough and the link will show you how to find your private (or local) IP address. Though it needn’t be private. Security by obscurity is not security – and it’s trivial to learn. But, that’s an article for another day.

I was able to quickly learn that my local IP address is 192.168.215.88. From this, I realize that the most common configuration will be for everyone to be on the same subnet and so my laptop likely falls within the 192.168.215.1 to 192.168.215.255 range.

We can use the asterisk to represent any of those numbers, as it’s a wildcard. This means the next command is obvious and will be simply:

The -sn flag would mean ‘do not do a port scan’, so it’s checking only for devices that return a ping. Make sense? (It’s a pretty speedy command when not also scanning ports.)

A Picture Of nmap:

I think that this is one of those instances where my text isn’t quite clear enough. So, what I’m going to do is show you a picture. 

The nmap command I ran showed me a list of local network devices. As I already know the IP address of the device I’m using, I can exclude that from the list. The device I’m looking for (my laptop) is then a different IP address.

The process looks something like this (trimmed down to just have one device for simplicity’s sake):

using nmap to find local network devices
As I know my device’s IP address, I can exclude that from the list of possible IP addresses.

As you can see, I first tried to connect with the .local domain and found that it did not work. So, I ran the nmap command and used a wildcard to scan the entire IP address range (1 to 255).

Sure enough, the IP sweep with nmap found another device and showed the IP address. It showed the gateway, which I could also exclude. The process of elimination meant there was one IP address to try (it could have contained more devices). I tried to use SSH with that IP address and, sure enough, that’s my laptop!

See? I saved a trip across the room! I saved opening up a bulky application and waiting for it to do its thing before I could even try using it to connect to the laptop. In fact, I suppose I also saved the effort I could have spent just randomly guessing IP addresses and hoping I got the right one for my laptop eventually!

Closure:

I figure there’s a lesson in nmap in there somewhere. You never know when you’re going to need to find local network devices! Now, when you do need to do so you will know how.

I figured I’d try writing this one in a way that showed you how I benefit from knowing how to do this. I figured that it’d be interesting to show you how the command solves a real problem. There have been a few articles similar to this and they’re fun articles to write. They are articles that come from the real me, the me that is actively using and appreciating Linux (often in the terminal) in my day-to-day life.

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How To: Use An Older Version Of A Google Chrome Extension

Today we’ll cover a not-so-serious topic about how to use an older version of a Google Chrome extension. There’s a subset of my readers who may eventually want to know this information. It might not be today, it might not be tomorrow, but someday you may need this information. 

Fortunately, that information will be right here in an article about how you go about using an older version of a Chrome extension. This is one of those things you don’t need – until you need it. It’s kinda like how I answer kids who ask if I have any good life advice; “But a plunger before you need a plunger.” It’s pretty solid advice.

The gist of the story is that I live in a very remote area. I also live where weather events are (and this is not in jest) sometimes fatal. If you’re unprepared for the cold, it can kill you. Of course, it’s unseasonably warm right now – but that doesn’t change the point.

So, I take the weather a bit seriously. One of the tools I use for cursory weather examination is a browser extension called “Forecastfox.” The extension relies on AccuWeather and folks have determined that it’s an API change that broke the extension. Also, to make it a bit more interesting, the author of the extension is in Ukraine.

It could be a while before it is fixed and operating properly. Fortunately, and for whatever reason, the previous version was known to still work. Unfortunately, it is a bit of a hit-and-miss, but it’s sometimes possible to get an older version of a Chrome extension. It’s then easy enough to install it, which is what this article is all about.

Use An Older Version Of A Google Chrome Extension:

When you find a Google Chrome extension (and this applies to Chromium, Opera, Brave, Edge, and all the other Chromium-based browsers out there) that doesn’t work anymore, you have some options. You can try a previous version, an older version, to see if that still works as expected.

Unless it’s a security extension, or unless the extension had a security-related flaw, it’s reasonable to try an older version of the extension to see if it works. In my case, I did a bit of research before choosing this route – and I’d advise you to do the same. Make sure the update was just bug fixes and feature additions and that you’re not reverting to an extension with known security issues.

Once you’ve looked around and determined that using an older version of the extension is a good idea, you can get to work on using an older extension version. You’ll want your browser open for this. In this instance, we’ll be using Chrome.

Your first real step is to click the three-dot menu in the upper right. Then, open “More Tools” and click on “Extensions”. In the upper right, enable “Developer mode”. It looks like this:

Enable developer mode in Google Chrome.
Have you ever wondered what this switch was for?

With that enabled, your next step is to find and download an older version of the extension. Be sure to remove the existing version before going any further. Additionally, leave that extension page open because you’re going to need it again.

Now to find an older version of your extension. Start by searching here:

https://www.crx4chrome.com/

That site has a whole lot of extension versions backed up. Odds are very good that you’ll find an older version of your extension there. If you don’t find one, you can try going to the extension’s home page or checking code repositories like GitHub. For example, if it’s on GitHub, just look to the right sidebar to find the releases link and look in there.

Once you have that file (it should be a string of letters and numbers that end in .crx) just drag it to your Google extension page. There’s nothing fancy, just left-click on the .crx file and drag it to Chrome’s open extensions page.

That’s it. It’s that simple.

As you manually loaded the extension you shouldn’t need to worry about it updating automatically. It shouldn’t automatically update until you’ve installed the current version from the store again. So, you’re good to wait for a version or two with your working extension. Then, once you’ve determined the current version works, just remove the extension you manually added and install the version from the store.

See? You’re done!

For Our Firefox-Using Friends:

If you use Firefox add-ons, I did look up how to do the same thing with Firefox. It’s much easier to do this with Firefox. I don’t use Firefox all that often anymore, but I figured I’d learn how to load an older add-on and share that information with you. 

If you’re a Firefox user, you’ve got it easier – mostly…

Your first step is to click the three-line menu, where you’ll select “Add-ons and themes”. Open up the add-on’s settings so that you can remove the extension. After you remove the add-on, leave that tab open because you’re going to need it again.

Once you have the add-on removed, find the add-on’s home page on the Mozilla Add-On site. Look on the left and scroll down. You’re looking for “More information” which should have a “See all versions” link. Click on that and download an earlier version. It’d look something like this:

click that link to download older versions of firefox add-ons
It’s not too hard to find. Click it. You’re almost all the way there!

On the next page, scroll down to find the add-on’s older version, the version you believe will still work. It’s a bit uninformative, but just click the older version’s download link on the right and it will download it and ask if you want to install it. Of course, you’ll pick yes to install it.

Now, go back to the tab that you were using to show your add-ons. Find the extension you just added and open up its properties (it’s ‘Manage’ under the three horizontal dot menu). Scroll down to find “Allow automatic updates”. Click on “Off” to disable automatic updates so that it doesn’t automatically update your add-on to the newest version.

When you are reasonably sure that the current version of the add-on will work with your system, you can just enable automatic updates. That should do the trick but will take time as it’ll just update when it next checks. You can simply remove the add-on and add the current one after that, should you be in any sort of hurry.

And, for you Firefox users, that’s it! That’s all you should have to do if you want to use an older version of a Firefox add-on. It’s not too taxing, now is it?

Closure:

Alright, so it’s another long article – and another one that doesn’t require an open terminal. This time around, we’ve talked about how to use an older version of a Google Chrome extension. I also covered how to do so with Firefox. Ordinarily, I’d have considered making these two separate articles, but I figured you could handle another long piece. 

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Show A Specific Networking Interface

Today, I’m just going to write about a simple task, how to show a specific networking interface. This seems like a good short article.  It won’t be too complicated and it’s suitable for a beginner. Read on, if you are interested in learning how to get the information for just a specific networking interface.

It’s also suitable for most people, as most people only need information from a single, specific networking interface. Most folks reading this site are home users of Linux and it’s quite likely that they’re only connecting over one network interface, be it ethernet or wifi. Frequently, you only need to show a specific networking interface when gathering information from the terminal.

If you’re still using ‘ifconfig’ you can close this tab immediately. The tool is deprecated and we’ll just be using the ‘ip’ command. Odds are good that your distro has already moved away and is using the ip command. If your distro hasn’t done so, it should be noted that the process of deprecating ‘net-tools’ (from which you get ifconfig) started in like 2001. You may still have the legacy tool, but we won’t be covering it.

Anyhow…

That’s a long intro for something this short…

Show A Specific Networking Interface:

This is yet another article that requires an open terminal. So, crack open your favorite terminal. 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.

With your terminal open, you can run the following command:

You can even run:

Or, you can get that information for a specific networking interface. To do so, we just use the first command, like so:

For example, if your NIC is called ‘eth0’, the command would look like this:

The output from that command will be just the information about that specific networking interface. You won’t have the clutter of the first two commands listed and it will only show the device you specify. If you’ve only got one network interface in use, you can just store the final command in your memory for when you need to check some of your networking information.

Closure:

See? I told you that it’d be quick and easy. Not all of these articles need to be long and complicated. Besides, my 2-year anniversary is coming up, meaning a short and simple article is a good thing. I don’t want to burn out or anything, not at this stage of the game.

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Another Way To Find A Website’s IP Address

Today’s article will just be a fun one, where we cover yet another way to find a website’s IP address. It’s mostly for fun but it’ll also introduce you to another tool for your terminal-toolbox. After all, there’s almost always more than one way to do things in Linux, including finding a website’s IP address.

So, today we’ll be using a tool I don’t think I’ve covered before. While we have done the website IP address thing before, I don’t see the ‘nslookup’ tool anywhere in the site’s history. We might as well, as I could use a quick and easy article today, as I’ve been busy making a delicious ham.

Odds are good that you have nslookup installed by default. If you don’t, it’ll be easy enough to install with your package manager. If you check the man page, you’ll find the tool describes itself as:

nslookup – query Internet name servers interactively

And, yeah, that’s what we’ll do with nslookup. We will use it to do what it’s designed to do. We do that often around here and, of course, we’ll be doing all this in the terminal. I’m sure there’s some GUI tool you could use, but every Linux distro that I know of comes with a terminal. It just makes good sense for most articles!

Well, that’s enough blathering about what you’re going to read…

Find A Website’s IP Address:

As the intro mentioned, we’ll be doing this in the terminal. So… Open a terminal of your choosing. If you don’t know how to open the terminal, you can do so with your keyboard – just press CTRL + ALT + T.

With your terminal now open, the syntax is simple:

You’ll often get more than one IP address in the answer, but that’s because sites will often respond on more than one IP address. For example (and considering that I’m behind a CDN), this site would look like this:

it's easy to find a website's IP address
See? It’ll answer on an IPv4 or an IPv6 address at this time. Pretty easy, huh?

Go ahead and try using nslookup to find the IP addresses of your favorite sites. There’s no harm in doing so and it can be a useful bit of information – though usually, that’s more useful for the site’s admin. Still, it can be a handy bit of information.

Closure:

There! See? Another quick and easy article. This time, we’ve shown another way to find a website’s IP address. It’s not complicated and the output is easy enough to process. Enjoy the tool and have fun with it.

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

How To: Restart SSH

Today’s article will be a very short and easy article, where we learn how to restart SSH. This involves restarting the SSH service. It may not even require a second section, it’s that easy. No, it probably will, just to keep things uniform. So, to learn how to restart SSH read on!

This one is drawn from my own frustration. I recently have had to deal with this a couple of times and I’m not sure why. I’ll root through the logs to figure it out at some point, but the obvious issue here is that I had issues with SSH stopping. More specifically, the SSH daemon/service stopped running.

In my case, I was able to just use another remote connection to the device. I suppose I could have just walked across the house, but it was easier to just use TeamViewer.

Oddly, I’ve had TeamViewer cause problems before. I even have an article detailing how to restart TeamViewer from the terminal (via SSH, I suppose).

So, rather than rebooting the system, I just connected via an alternative method and restarted SSH. It’s easily done.

Restart SSH:

You’ll first need some way of connecting to the device with the stopped SSH service. In the opening section, I mentioned doing so with TeamViewer. It pays to have a backup method to connect to your servers, so you could use VNC or something else that works for you.

If you physically go to the device, or remotely connect to the device, you’ll need a terminal to work with. So, open a terminal. Depending on how you’re connected, you might have to find the terminal in the menu as not all keyboard shortcuts will be passed to the remote computer.

So, once you have a terminal open on the remote computer, try this command:

If that doesn’t work, try this command:

One of those should work for you. Make note of which one works and you, if you think you’ll be doing it often. You can also ‘stop‘ and ‘start‘ services, easily enough, but just a restart should do the trick.

Closure:

See? I told you that it’d be quick and easy. I could use a quick and easy article right now, and this subject just happens to be something I’m currently thinking of. So, you get this as an article, an article about how you restart SSH. Simple and easy…

Thanks for reading! If you want to help, or if the site has helped you, you can donate, register to help, write an article, or buy inexpensive hosting to start your own site. If you scroll down, you can sign up for the newsletter, vote for the article, and comment.

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