Category: Networking

‘traceroute’ in Linux, Let’s Take a Closer Look!

This article will explain a little about ‘traceroute’ as a network diagnostic application. We’ll give a few traceroute examples, enabling you to figure out some networking issues.

Whenever I find myself unable to connect to a networked device, including websites online via the internet, one of the first tools I reach for is called ‘traceroute’. It’s not exclusive to Linux and you may know of the tool ‘tracert’ in Windows that does the same thing.

traceroute defines itself as this:

traceroute – print the route packets trace to network host

More realistically, it shows you the hops (devices) you go through in order to make a connection. See, when you connect to a different computer over the network, you don’t generally do so without going through other devices. Your data will travel through multiple devices to reach the source device and all those hops along the way are potential points of failure.

Sometimes those devices are under your control and you can actually do something about it. Other times, it’s just informative and all you can do is wait, or inform someone else and hope they fix it. If nothing else, you’ll know where your packets stopped or slowed down to the point of uselessness.

For example, there 13 hops (devices) between me and linux-tips.us.

traceroute in action
See? There are 13 hops to reach my destination. 

So, while that picture should explain it well enough, let’s get a little deeper.

Using traceroute:

You may find that traceroute isn’t already installed. If it isn’t, it’s absolutely in your default repositories. However you would normally install software is how you install this. If you look, traceroute is sure to be in there. So, go ahead and install it if it’s not already installed. For example:

Just adjust that to your package management system and it’ll be in there. It’s that important a tool that I’m sure it’s in there. In fact, I’m a bit surprised that it’s not always installed by default, but it isn’t.

Now, the most basic usage is just like you saw in the image above.

So long as you’re within 30 hops and use 60 or fewer packets, that’s going to work well enough. The information it spits out is what devices it has traveled through (their hostname and IP address) and RTT – Round Trip Times. There are three of them because three packets are sent. Ideally, you’ll see your destination listed last. If not, you’ll see the closest you got to your destination.

If you see an asterisk, that means the device didn’t respond as expected. Frequently, this means the device is blocking ICMP. You can try to get around this by using ICMP ECHO (-I) or TCP (-T) packets. However, both of those will require elevated permissions, or the use of sudo.

All of this is mostly informative – unless you’re in control of the network and devices.

When it’s a network and devices under your control, you can use this information to troubleshoot. You can see the device names and time taken for packet transit, narrowing down your choices for troubleshooting.

When you’re using this over the public internet, you’re subject to other people who control the devices. If you find a break along the way, about all you can do is wait – or maybe use the data to contact your ISP (or hosting provider, if it’s your site that you’re trying to reach).

There are other options with traceroute. You can change the port you use, you can send more or fewer packets, you can not resolve hostnames, and more. To see the rest of the traceroute options:

That will fill you in with the many other choices you have. I find I don’t really need the advanced options, but system admins may need some of the features. As a regular user, I just use it to troubleshoot my own connections on my private network or when I am having web hosting/connectivity issues.

Closure:

And there you have it. Another article is in the books, and this time it’s just a nice easy article about the venerable traceroute. If you don’t already have this tool in your toolbox, it’d be worth adding and adding a basic familiarity to your mental toolbox.

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How To: Change The Port SSH Uses

There are a number of things you can do to help secure SSH, and changing the port that SSH uses is one of those things that many people change. That can help, but I feel it’s important to also mention that security by obscurity isn’t really good security.

By the way, I’ve already written a couple of articles about SSH. Feel free to check ’em out, as they may get you up to speed if you’re not already there. The first link should be the link you click if you need to learn how to get started.

If you don’t know what ports are, there’s a great Wikipedia page here. We’re talking about software ports and not hardware ports. They’re well-described as this:

At the software level, within an operating system, a port is a logical construct that identifies a specific process or a type of network service.

By default, SSH uses port 22, and everybody knows it. Well, everybody that’s interested in networking knows this. And, because of this, malicious actors will scan for online computers and then check port 22 to see if SSH is running. If they find the port open, they’ll possibly try to guess the password and keep trying until they get through. 

NOTE: There are a number of ways to secure SSH, including disabling password logins entirely and using things like fail2ban to limit login attempts. I’d expect articles on those subjects in the future, but they have not yet been written by me. I’m sure other sites will have information, so use a search engine if you’re wanting to learn about those things today. (I am never gonna remember to come back and remove this.)

So, one step you can take is to make SSH listen on a different port. You can do that in isolation or along with other security methods. It’s not the greatest security fix, because people can (and do) just scan entire port ranges. While moving the port to something other than the default will help, it’s (by itself) just security by obscurity.

Knowing all that, let’s take a look at how we can change from the default port to one of your choosing. It’s actually pretty easy.

Change Your SSH Port:

To get started, we’re gonna need to open a terminal. You can do this with your keyboard, simply press CTRL + ALT + T and your default terminal should open up. By the way, you can change your default terminal.

Once that’s open, we’re going to want to edit a file using nano. You’ll do that with this command:

That will open ‘sshd_config’ (the SSH configuration file) with the nano text editor. Once that’s open, you’re going to scroll down while looking for “#Port 22”. It will look a little something like this:

changing the port SSH uses
For many of you, the next step will be obvious!

What you need to do is remove the # and then change the 22 to whatever port you want to use. So, if you wanted to change the port to 4441, you’d change the line to read:

Note the removal of the #, as the # tells the computer to ignore that line. A line starting with # (in this case) means that line is ‘commented out’, meant to be ignored.

Anyhow, once you’ve changed it to the new port you need to save it. Seeing as you’re using nano, that’s pretty easy. Just use your keyboard and press CTRL + X, then Y, and then ENTER.

Just because you’ve changed it doesn’t mean it has taken effect. You have to restart the service. To do that, you need this command:

That should restart the service, where it will now listen on the new port. From now on, you’ll connect with something like this:

Basically you’re just adding the ‘-p 4441’, except whatever port you picked, to the command. If you’re using aliases or something like Putty, be sure to change those settings as well.

NOTE: This isn’t the final step for many people. Some of you will have to change your firewall’s settings to allow TCP on the changed port. In some cases you may also have to enable it with semanage utility. In those cases, consult your documentation. If you can’t get it figured out, leave a comment and we’ll see if we can get it figured out together.

Closure:

And there you have it, another article in the books. This time, you’ve learned how to change the port that SSH uses. Hopefully that’ll come in handy for some of you. In isolation, it’s not the greatest security method – but it’s better than nothing. There’s still an article every other day!

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.

How To: Rename Your Network Adapters in Ubuntu

For whimsy, or for whatever reasons you dream up, you may want to rename your network adapters in Linux. Well, you can. This article will explain how to rename your network adapters, from perhaps eth0 to whatever you want.

I can only be certain that this works in current Ubuntu LTS – 20.04, I didn’t test with any other distros. It’s pretty safe to assume that it will work with most distros out there.

Notably, I am just pulling this from my notes. I forgot why this is in my notes and I really can’t think of too many reasons why you’d need to rename your network adapters. Still, there’s at least one person who needed to know this information, else it’d probably have not been in my notes. It’ll almost certainly work with Debian, Mint, Pop!_OS, and others in that family of operating systems.

This article should be fairly short and will suggest the use of ‘inxi‘. As this article is based around Ubuntu, you can go ahead and install it with:

It’s a lightweight application that spits out a ton of information. I think it should be installed by default, but not all distros do. If you’re trying this with a non-Ubuntu distro, and one without apt, just adjust the installation method for your package management system. It’s almost certainly in your default repositories.

Rename Your Network Adapters:

The first thing you’re going to need to do is open your terminal. If you just installed inxi, you may well have your terminal already open. If not, you can open it with your keyboard. Just press CTRL + ALT + T and it should pop right open.

Once you have the terminal open, we’re going to use ‘inxi’ to get some information. The command you’re looking for is:

Specifically, you’re looking for the networking section. It should look a little something like this picture:

network information
Note the arrows. You need those two pieces of information.

You’re looking for the name of the adapter and the MAC address. You’ll want both of those bits of information, so you might as well keep that terminal open and open up another one. That’ll be easiest, as you can then just copy and paste the data in the next step.

Now, you need to create and edit a file. We can more or less do this with a single step. In the 2nd terminal, use this command:

Once that is open, you want to add some text to it. This is the template:

Now, to use that template, you insert the MAC address that you got from the inxi command where you see <mac_address>.

The <device_name> is a bit more tricky. It’s usually the first three letters – and don’t forget to leave the asterisk there. So, if you use my image above, you’ll see it’s wlo1. To change it, you’d just use ‘wlo*’. If it’s ‘eth0’ for your network adapter then you’d change it to ‘eth*’ being careful in all instances to keep the asterisk.

The last field to change is the name. You can stick anything you want in that field. So, for me, the command will look like this:

Yes, yes I really did name it booger. I’m pretty much a giant five year old.

When you’re done, save it. Just press CTRL + X, then Y, and then ENTER to save it with nano. As it’s creating a new file, it may ask if you want to create said file and you should (of course) say yes.

That’s it! Just reboot and you should see that you managed to successfully rename your network adapter. If it doesn’t work, double-check to make sure you got the device name and MAC address correct and reboot again. Done successfully, it looks like this:

renamed network adapter
Yes, yes I really did name it ‘booger’ – but only in a virtual machine.

See? It works!

Closure:

Again, I’ve only tested it in Ubuntu – so it’ll likely work with any Ubuntu derivative, should work for Debian, and will probably work with any other mainstream distro. I forget why it was in my notes, but I’m sure it was useful for someone. Maybe they just needed a name they could recall a bit easier, perhaps for their wireless connection and they wanted to connect to it in the terminal instead of keeping it always connected? I dunno… It was in my notes, it’s now online.

Either way, there’s another article. Thanks for reading! If you want to help, you can donate, register, write an article, or buy cheap hosting. When you scroll down, you can comment, vote for the article, or sign up for the newsletter. Should you sign up for the newsletter, I won’t share your information with anyone else and I won’t send you any spam.

‘vnStat’ A Tool For Monitoring Your Bandwidth Usage

‘vnStat’ is a wonderful tool for monitoring your bandwidth usage. This article will show you how to use vnStat effectively. For bonus points, we’ll also look at ‘vnstati’ so you can make pretty graphs to visualize your bandwidth usage. This article shouldn’t take too long!

‘vnStat‘ stands for ‘view network statistics’ and has been around for like 18 years at the time of this writing. It’s so common that it has its own Wikipedia page. Of course you know that already, you can see the handy link I already provided!

Anyhow, ‘vnStat’ is a tool that runs in the terminal, a console tool as it helpfully describes itself:

vnstat – a console-based network traffic monitor

It’s a pretty great tool that generates some neat information and displays it in the terminal. It looks a little something like this:

vnStat in action!
See? I’ve stopped taking screenshots with a semi-transparent terminal! I’m pretty much a pro!

That image should save me a whole bunch of time! I trust that my readers are smart enough to figure out the gist of it with just a handy screenshot. For those not fluent in the ways of vnStat, ‘rx’ means received and ‘tx’ means sent. The rest should be pretty easy to figure out.

Install vnStat:

In order to get vnStat, you have to actually have to install it. It’s available in the default repositories in the popular distros (and even the BSD family). If it isn’t, you can always build it from source. But, you can probably install it much like you’d install anything else. For example, in a distro that uses apt you’d install it with:

(We might just as well install vnstati at the same time. Also, adjust that command for your own package management system.)

You can next go ahead and enable the service and start it next. That will be:

Once it is installed, you should set up database(s) for vnStat. This is done with:

Where you have “<device_name>” you replace it with the name of your internet adapter. For example, lots of Ethernet adapters are ‘eth0’. You can find the name of your adapter(s) by using either ‘ifconfig -a’ or ‘ip addr’. You can repeat this with all the names of the internet adapters you use, if you do in fact use more than one.

Then you can verify your vnStat installation with:

Assuming that spits out a version number you should be good to go.

Using vnStat (& vnstati):

So, by now you should have vnStat installed, and its sister app vnstati should also be installed. Let’s examine how you use them.

First, you can just call the application in the terminal. There’s nothing complicated about it and it may be your choice if you have more than one network interface. To do so, it’s just:

You can also be more specific, getting the data for just a single device:

Where ‘eth0’ is, change it to the name of your device. So, for a wireless device, it may look something like:

There are a ton of other options, so be sure to check the man page. Those are the options that I use most often, so those are the only ones we’ll be concentrating on.

Now, you can also use vnstati to make a nifty graphic that will show you your bandwidth usage. It looks a little something like this:

vnstati in action
That’s the graphical outcome I prefer.

That’s the output of this command:

As you can guess, you can change the output path to anything you want (and have permissions for). I prefer that particular graphic, but there are a ton of options and you can gather all sorts of information. For example, there’s also this to show the hourly rate from the past 24 hours:

vnstati in action
This is an hourly output, which may be of value if you have limited bandwidth.

That is the output from this command:

And, again, you can modify the outputted .png to place it where you want. There are a whole lot more options and this article isn’t going to cover them all. That’s not the kind of article I write. There are tons more options in the man page, if you want to explore them.

Find what works for you and run with it. You should be able to find a format you like that has the information you’re looking for. I’m just introducing you, you decide how you use it.

Closure:

And there’s another article in the books! This one explains vnStat and vnstati. Both are pretty great tools that go well together, and they help you monitor your bandwidth usage. If you have any questions or comments, feel free to scroll down and leave a message.

Thanks for reading! If you want to contribute, you can donate, you can write an article, you can register to help, you can buy inexpensive hosting, you can rate the articles, you can scroll down to sign up for the newsletter, or you can share this site on social media. If you can think of anything else to help, jump right in and start doing it!

How To: Find Your IP Address Through Your Terminal

The answer to the question, “What is my IP address?” can have different answers. In practice, you likely have more than one IP address. This article will explain how and will tell you how to use your terminal to find your IP address(es).

What is an IP address?

An IP address is a numerical designation given to computers on a network. This number is used to identify the computer. You can also identify a computer by their hostname, but the hostname is resolving to an IP address. Computers that are connected to a network will have an IP address.

There are two types of IP addresses to be curious about these days. There’s IPv4 and IPv6. IPv4 predates IPv6 and is still in use, but has run out of numbers. IPv6 solves that by enabling a whole lot more combinations. IPv6 has a potential of 340,282,366,920,938,463,463,374,607,431,768,211,456 addresses – which is a whole lot of ’em, especially when compared to IPv4’s paltry ~4.3 billion addresses.

IPv4 addresses have technically already been exhausted, and have been since early 2011. The addresses still exist, but they’re all assigned to various entities. The IPv6 roll-out has been slow. Odds are good that you’re using IPv4 right now, in fact I know you are – as this site has an IPv4 address. Still, your router is likely handing out IPv4 addresses and your ISP is likely still using IPv4 addresses.

Additionally, in most cases, you would be concerned with two IP addresses. You’re likely connected to a router/modem that’s connected to the internet. As such, you will have a private IP address and you’ll have a public IP address. The first is (usually) assigned to your computer by your router and the second is assigned to your router by your ISP. This article will explain a little about each and how to find both of them.

Find Your Private IP Address:

Your private IP address will be in a reserved section of the IP address space. It will probably be handed down by DHCP (Dynamic Host Configuration Protocol), but many routers will both let you pick your IP address (from the reserved space) or will just assign the same IP address to the same device based on the MAC address (Media Access Control). 

The reasons you’d want to know it are your own, but it’s handy if you want to connect to a specific computer. As I know my laptop is 192.168.1.5, I can just SSH into it using that address. I know my media server is a different address, and I can connect to it with the IP address as well.

There are a number of ways to find your private IP address. I’ll share two of them that are quick and easy. For this, you’re going to want to open your terminal, which you can do by pressing CTRL + ALT + T and it should open right up.

First try:

You can also try:

In both cases, you look for ‘inet’ AND your device. You’re not looking for ‘loopback’, as that will likely list your IP address as 127.0.0.1 – which isn’t the address you’re after for reasons beyond the scope of this article.

You’re looking for your device, maybe named ‘eth0’ or ‘wlo1’ or similar, and then you’re looking for ‘inet’. Your IP address is the next four sets of digits (or alphanumeric combinations in the case of IPv6). For example:

example IP address
I’m not so sure the underlining matters.

One or both of those methods should work for you with any major distribution. There are surely many other ways to find your IP address, so feel free to leave a comment indicating how you do it.

Find Your Public IP Address:

The next kind of address is your public IP address. This is the IP address your ISP assigns you. If you wanted to connect to your computer over the world-wide-web, you’d be able to do so (with obvious caveats and proper configuration) with your public IP address.

It’s also the address I see (unless you’re using a VPN) in my server logs when you visit my site. That’s perfectly normal – as my site needs to know where to send the return packets. If my site didn’t know an address to send data to, it simply wouldn’t work.

You can think of this as the IP address assigned to the public side of your router, and your router then passes that information along via the private IP address that originated the request. This lets you have multiple devices using the same public IP address. (Read about NAT here.)

My understanding is that some ISPs are NATing public IPv4 addresses so that multiple routers can actually have the same IP address (not necessarily a good thing). However, that too goes beyond the scope of this article and isn’t want this site is actually about.

Anyhow, there are numerous public servers out there that you can ‘cURL‘ and those will give you your public IP address right there in the terminal. Just like above, you can open your terminal by using your keyboard and pressing CTRL + ALT + T. Once open, you can try:

Or you can try:

It should look a little something like this:

my public IP address
Yes, that’s my public IP address. No, I don’t care.

There are numerous other sites that’ll spit out the same info. The top-most example was recently handed over to Cloudflare, just so folks are aware.

Closure:

And, there you have it. You now know how to find your public IP address and how to find your private IP address from within the terminal. There are also many dozens of websites that will tell you your public IP address, but we might as well stick to the terminal for this one. Why not? You can do a lot in the terminal.

Once again, thanks for reading. Your comments and feedback help make the site better. As always, you can donate, write an article, sign up for the newsletter below, register, and vote to let me know which articles you prefer. If you sign up for the newsletter, you’ll get notifications when new articles are published. No spam, I promise!

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