Category: Command Line

Monitor Network Usage On A Per-Application Basis

Today’s article is going to tell you how to use Nethogs to monitor network usage on a per-application basis. It’s actually easier than one might think and we’ll even show you how to install Nethogs on a variety of distros.

Why would you want to monitor this? Well, you may want to know which applications are eating up most of your bandwidth. Not everyone has unlimited bandwidth after all. You might also be looking for rogue applications/malware that’s using up some of your bandwidth. There are all sorts of reasons to monitor your network usage at this level. Feel free to leave a comment telling us how you intend to use Nethogs.

As stated, we’ll be using Nethogs. The man page describes it as:

nethogs – Net top tool grouping bandwidth per process

I suppose that’s mostly useful to those who know what ‘top‘ is. (There’s a future article about top and htop, when I get to it.) But, Nethogs is like a system monitor, except it’s a network monitor with some visual similarity with top. (Yes, that’s an ugly, ugly sentence.)

We’ll be using ‘sudo’ for all of these commands. It’s possible to use Nethogs without sudo, but we won’t be covering that here. If that’s something you’re interested in doing, a search engine will help you get there.

Monitor Network Usage:

Nethogs is a terminal-based application. As such, you’ll need an open terminal. Just press CTRL + ALT + T and your default terminal emulator should open right up.

Once your terminal is open, you can go ahead and install Nethogs. Pick the command that works with your system’s package manager.

Debian/Ubuntu:

RHEL/CentOS (will need to enable EPEL):

Fedora:

Arch/Derivatives: 

Once you have Nethogs installed, you can check the help files. In this case, the help files are better than the man files (I think) so just enter the following into your terminal:

Now, to run Nethogs, we’ll use sudo and just run it in the terminal. Believe it or not, this mode is generally just fine for anything you’re going to do.

That’ll open Nethogs and start monitoring your network usage on a per-application basis. It looks something like this:

Nethogs running in the terminal.
As you can see, bandwidth monitoring on a per-application basis. Tada!

Now, if you’re going to leave it open, you can change the refresh rate. That’s done with the -d <seconds> flag. If you want it to refresh every 15 seconds, your command would look like this:

By the way, if you want to exit Nethogs, you just press Q and it closes – like top and htop do.

If you want, you can specify the network interface you want to use. It doesn’t require any flags, just the network interface name. (Read Also: how to change your network interface name.) An example of that command would be:

While the application is running, you can do some sorting/display changes with the M, R, and S keys. But it’s usually not all that complicated and sorting isn’t needed. If you’re dealing with hundreds of collections, then you may want to start sorting. Really, that’s about all you’ll ever need.

Closure:

And there you have it! You have another article to read. This one is about monitoring your network usage on a per-application basis, a pretty handy skill/tool to have. It’s pretty easy and the output is clear enough for all but the newest Linux users. If you find the tool useful, or already use the tool, please feel free to comment.

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Upgrade Ubuntu From The Terminal

Today’s article will show how to update and upgrade Ubuntu from the terminal. Of course, this will work on any system that uses apt, including Debian, Lubuntu, Linux Mint, etc… You can always upgrade when the GUI tells you to, but you can do it manually on your own time.

Once in a while, I come across someone who refuses to upgrade. This is a bad idea. Upgrades include things like security upgrades and they’re pretty much mandatory. It’s Linux, so you don’t “have to”, but it makes you a bad netizen because those security upgrades may very well mean your computer is being used as a spam relay or, worse, a part of a botnet.

So, please, upgrade your Ubuntu systems – and, really, all Linux boxes should get regular upgrades. I can’t emphasize this enough! Upgrade your system – if not for you then for the rest of us who have to deal with enough internet hostility. Malware exists for Linux, as does exploits for Linux and the software you have installed. Even if you don’t care about your own experiences, care about the rest of the people on the ‘net. Thanks!

For this article, we’ll be using apt. Apt is apt-get in disguise, but not quite the same. If you’re scripting you use apt-get, because it’s more stable. When you’re running commands yourself, use apt because it’s faster/easier. 

This article should be pretty quick and easy.

Upgrade Ubuntu From The Terminal:

Obviously, this article requires an open terminal. You can open one with your keyboard – just press CTRL + ALT + T and your default terminal should open.

Once you have your terminal open, we’ll go ahead and update the database (the cache) to see if any upgrades are available. To do that, you run:

It’ll tell you if upgrades are available and give you some more information – such as telling you how to see which application upgrades are available. In this case, we’re just going to upgrade everything. Like so:

That is sometimes interactive. It will want you to agree manually to the upgrades. You can just skip all that by adding a -y flag. Even better, you can now string both commands together and save some time monitoring the terminal. That command, and I use this pretty much exclusively by way of alias, is:

The && means that the next command will only run if the first has been completed successfully. You can even add autoremove to this string of commands and keep things a little cleaner automatically.

The autoremove will “remove packages that were automatically
installed to satisfy dependencies for other packages and are now no
longer needed as dependencies changed or the package(s) needing
them were removed in the meantime.” You might as well include it, as it’s pretty harmless and will save you some disk space.

Finally, there’s full-upgrade which is quite similar to the old apt-get dist-upgrade, in that it will upgrade you to a new release if both a new release is available and your settings are to upgrade to new releases (instead of staying on a LTS branch, for example). You’ll find that full-upgrade is also capable of deleting unneeded files all on its own.

To use full-upgrade, you’d still run the update first and then run the command. You can also pack them together, like so:

And there you have it. That’s about all you really need to know about upgrading Ubuntu from the terminal. It’s not hard, so just do it. Yeah, once in a blue moon it breaks something. That’s usually easily fixed and the risk is worth the benefits – to you and the rest of the internet.

Closure:

I can’t emphasize it enough – do your upgrades regularly. Now you know how to upgrade Ubuntu from the terminal, which is something I naturally do out of habit. I actually have it aliased to the ‘update’ command and it takes care of all that for me. I can’t remember the last time it broke anything – but it has to have been multiple years ago. Breakage isn’t a real risk, as things are usually heavily tested.

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Show Date And Time In The Terminal

Today’s article is a nice and easy one, where I show you how to show the date and time in the terminal. It seems like a nice and easy article to write when I’m not feeling well. I’ll try to not let my ailments hamper the article in any way. 

Normally, I’d have a few articles written ahead of time. This time, I only have one article written ahead of time and it’s my ’emergency’ article. I’m not doing that poorly, so I’ll write this one. I’m pretty dedicated to doing an article every other day.

Anyhow, as I said, this article will show you how to get the date and time from the terminal. You can actually get the time just from running uptime, but there’s more to it. Linux actually has a ‘date’ command, which is what we’ll be using for this exercise. The date command’s man page describes it like:

date – print or set the system date and time

We will only be using the date command to print the time in the terminal. There are easier ways to set and maintain the time. With NTP being common, you really shouldn’t have to worry much about keeping the time accurate enough on your system.

Why would you want to know the date and time? Not everyone uses a desktop environment with a GUI and a clock. You may need to know the system time when you’re working on it remotely. There are all sorts of reasons. In fact, I once wrote an entire article about finding your timezone in Linux.

Show Date And Time In The Terminal:

This article requires an open terminal, just like many other articles on this site. Just press CTRL + ALT + T and your default terminal should open.

Now, this is nice and obvious… With your terminal open, just type in:

You’ll get an output similar to this one:

Tada! You’re done!

Just kidding! There’s more to it. If you want to show just the time, you can just use this command:

If you want to show the date and have it formatted like we do in the US, you can use this command:

Want to know the date 3 weeks ago? (You can also use days for this command)? Well then, you can try this command:

How about if you want to know how many days into the year you are? Well, you can do that with:

Those are about the most interesting ways to show the date and time in the terminal, at least the most interesting ways that I can think of at this moment in time. If you use the date command for anything else, let us know by leaving a comment!

Closure:

There you have it, yet another article! This one shows you how to show the date and time in the terminal, just in case you want to do that. It’s a nice and easy exercise and, as far as tools go, is one that’s at least easy to remember. It’s probably not the most important tool you can have in your toolbox, but at least it’s in there. (Please be gentle pointing out any errors, part of this article was written with the help of a heating pad.)

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How To: Shutdown Linux From The Terminal

Today’s article is going to tell you how to shutdown from the terminal. I’ve previously explained how to reboot a ‘frozen’ Linux system using the Magic SysReq keys. Today, we’ll shutdown from the terminal. It’s a quick and easy article – as the holidays are eating a bit of my “free” time.

Why would you want to do this? Well, if your Linux system isn’t quite frozen or your desktop GUI isn’t something you can reach, then you may want to press something like CTRL + ALT + F3. That should crack open a TTY where you can login and issue commands to your system. Maybe you’re working on a server and need to shut it down? Who knows, but the command is there and it’s a useful command to keep in mind.

For this article, we’ll mostly be using the shutdown command, and the man page defines it as:

shutdown – Halt, power-off or reboot the machine

And it does pretty much what you’d expect from such a command. However, it’s not just a basic command, there are flags and some options that go along with it. So, we might as well take the time to learn about it. After all, you never know when you want to shutdown Linux from the terminal.

Shutdown Linux From The Terminal:

Like oh so many articles, this one will require an open terminal. If you’re connected to a remote server via SSH, you already have a terminal to work with. If not, just press CTRL + ALT + T and your default terminal should open.

Once you’re ready to shutdown your Linux system, you can enter the following to shutdown immediately:

Obviously, that command will shutdown the system immediately, so don’t practice it unless you plan on shutting down – ’cause you will. You can even shutdown at a specific time by using this format (and 24h time):

You can also use the +MM function. To shutdown in 10 minutes, you’d use a command like this:

If you change that +10 to +0, it will also shutdown immediately. If you have users of the system who should be notified of an impending shutdown, then you can actually send them a message. That would look like:

So, what happens if you schedule a shutdown and need to stop it for some reason? Fortunately, the shutdown command will let you cancel an impending shutdown – so long as you get there in time. That’s done with the -c flag, of course.

If your cancellation will impact the users, you can even include a message in that. It’s done like this:

And that’s about it, really. There’s a bit more to the shutdown command, but it’s mostly going to be used in one of the ways mentioned in this article. If you want more information about the shutdown command, simply run man shutdown and read the help file.

Closure:

And there’s another article. This one will tell you how to shutdown Linux from the terminal, a handy skill to have as a user or as an admin. It may seem like a pretty basic command, but that doesn’t mean it can’t be included on the site. 

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Let’s Use ‘ls’ To Sort Files By Time

Today’s article is going to tell you how to sort files by time while using the ‘ls’ command in the terminal. I find sorting by time is often easiest when working with a lot of files that have less-than-helpful filenames. For example, it’s nice to sort by time when I’m dealing with screenshots, knowing that I took a new screenshot that’s helpfully named something like ‘kgiii@kgiii-msi: ~-Downloads_032.png’.

It’s usually easy enough to graphically sort files by time and date. In your file manager, you might need to select list view, add the column, and then select at least one of the time options. Different GUI file managers will have different options, and may not include all possible time values stored in the file’s meta information. Speaking of screenshots, it might look something like this:

sort by modification time
In this case, arranging items by ‘modification time’ is an available option.

The file’s metadata has several time options and we can sort by those with the ‘ls’ command while in the terminal. The output of ‘ls’ is usually sorted alphabetically. It’s not terribly difficult and will help you along your Linux trails. I find it useful when picking among a large number of files.

Parsing the output of the ‘ls’ command is generally considered a bad idea. We won’t really be doing that, but this is a good time to mention it. If you don’t know why, click this link. They explain it better than I can. That’ll save some time!

Today we will learn to use ‘ls’ to sort files by a few time value stored in the file’s meta information. It’s an easy enough process and a handy tool for your growing toolbox of Linux commands.

Sort Files By Time:

Obviously, you’ll need an open terminal. You can do so with your keyboard – just press CTRL + ALT + T and your default terminal should open.

Once you have it open, the /home/user directory is a fine choice. We won’t need to change directories – but you can. If you have a lot of screenshots saved in ~/Pictures, then you may find that directory more informative. Either way, let’s start with the basics:

This first one will show the last time the file was modified – which may be the creation date and time. That command is (the -l used in each command means use the long listing output):

You can sort by access time, sorting by the last time the file was opened. (Yes, this is all part of a file’s metadata.) To do that, you just use:

With that done, we have one more. This one shows the last time the metadata was changed for the files listed. If you were to use touch to change the last modified time, this would show when you did that. Make sense?

And there you have it! If you want to show the output in reverse order, you just use a -r flag and you can still use the -a flag to show hidden files, should you need to do something like that.

Closure:

That’s about it. You can now sort files by time. It’s a pretty handy tool and one you may find yourself using often. As mentioned above, I find it handiest (with my particular uses) when working with all the screenshots I take. I take a whole lot of screenshots. I assume I take more screenshots than most folks.

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