Category: Command Line

Disable Bluetooth From Automatically Starting At Boot

In today’s article, we’re going to learn how to disable Bluetooth from automatically starting at boot. It’s a handy thing to know, if you’re like me and have no real use for the service.

I suppose it’d even speed your system’s boot time a trivial amount and reduce the number of running services. So, it’ll make your system a trivial amount more efficient. I just don’t care for Bluetooth so I have a way to prevent it from automatically starting in my notes. These articles are generally based on my notes, so now you’ll know.

NOTE: I should probably also mention that this is really only useful for those of you who use systemd. If you still haven’t moved to systemd, or refuse to move to systemd, then this article isn’t going to be of much use to you. You can still do this, but you’ll have to do so with your particular init system’s commands. These commands are not gonna work for you.

Even if you don’t want to disable Bluetooth from automatically starting at boot, you may want to learn how to disable other services. The process for other services is pretty much the same as it is for Bluetooth. So, you can learn something from this article if you’re new to this whole thing.

This is a nice and easy article, it shouldn’t take much time to read and understand. So then, let’s get on with it!

Disable Bluetooth From Automatically Starting At Boot:

Yeah, that’s longer than it should be. Oh well… Blame the need to optimize for keywords! I try to keep ’em shorter, but here we are…

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.

With your terminal open, let’s first check the Bluetooth service status:

It may or may not be running. If it’s not running, odds are that Bluetooth isn’t set to automatically start at boot. You can ensure that it’s not set to automatically start with the following command:

Now, that’s the command you probably want. It’ll disable Bluetooth from automatically starting at boot – and it will still let the Bluetooth service start if you want it to later or if something else in the system calls for it to start. You can reboot and make sure the setting has changed, if you’d like.

On the other hand, if you ‘mask’ the service, like we did in the How To: Disable Sleep And Hibernation on Ubuntu Server article, you won’t be able to start the service at all. That’s the biggest difference between ‘disable’ and ‘mask’, in case you’re curious. Both of these options are better than manually deleting the services, ’cause you can undo the setting fairly easily. In fact, to do so with the Bluetooth service, you just:

After which, you should check the status again:

And all should be well. You can now reverse it after you’ve chosen to disable Bluetooth from automatically starting at boot. See? Pretty easy and handy information to have for other services. By the way, if you chose ‘mask’ then you’d ‘unmask’ the service, which seems like an obvious way to do it.

Closure:

See? I told you that this one would be pretty quick and easy. I’m kinda amazed that I haven’t run out of ideas for articles yet! I’m still chugging along, well after the initial year-long scope for the site. If I can do it, anyone can! I’m still very much open to guest articles, within reason.

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How To: Protect a file or directory from being deleted or changed by root

The following article is a guest article that will teach you how to protect a file or directory from being deleted or changed – even by root. This is a handy skill to have as you may have files you want to ensure are never changed.

This time, I’m going to do very little editing – but not out of laziness, but because I really don’t seem to need to do much. I really only need to do some formatting changes and we’ll be good.

Note: I forgot to ask the author if they want me to disclose their name. It’s a little late in the day now, as they’re in another time zone entirely, so when they see this they can let me know if they want their name credited/anything linked from it.

Without further ado…

Protect A File Or Directory:

Sometimes we come across files/directories in Linux that we don’t want to be changed. It won’t be long before we realize making a file “read only” through the GUI of our desktop environment doesn’t work the way we want to because the root user is still able to alter that file.

In this article I’m going to show you how to protect ANY file or directory from being deleted or changed even by the root user. For this example I’ll use xorg.conf which is nvidia’s config file.

Files:

In order to make xorg.conf immortal, as I like to call this process, open terminal and type:

and press enter. To make sure the file has become immutable, which is what the +i stands for, open it as root in your favorite text editor (sudo gedit /etc/X11/xorg.conf). Some text editors will allow you to write new content to the file but they won’t allow you to save the changes because the file is already immutable. Other text editors won’t react to pressing keys and there will be a “read only” string in the title bar next to the file name.

Undoing a file immutable is pretty much the same, with the only difference being that instead of a + you must use a minus symbol:

Directories:

You can also make a directory immutable or even a set of subdirectories. For this example open your home directory in your favorite file manager, then open terminal and type:

Now, here comes a little tricky part that you need to remember for the immutabling of the directories to work: placing a slash after the names tells the shell that dir2 is a directory and not a file. If you type /testdir/dir2, the shell will think dir2 is a file and will return an error.

If you have entered the command correctly, you will see this output:

If you have closed terminal, open it again in your home directory where you just created these two directories and type (exactly the way you see it, with the capital R and V):

-R stands for “recursive”, meaning it will do the same operation to all subdirectories, including dir2.
-V stands for “verbose” which will display what has been done.

In order to test this, simply select test dir and press Delete to try and delete it. You’ll see an error message which means testdir and the dir2 inside it have both become “immortal” and now nobody can delete them, not even root.

Undoing this is the same command, only instead of +i, you must use -i.

Closure:

And there you have it, a fairly well written article that I didn’t do much to other than some basic formatting. If there’s an error, don’t blame me! Ha! It looks right to me and jives with what I know on the subject, but I did not actually go through and test this. I trust the author to know what they’re talking about.

By the way, if you have a favorite subject and want to write an article, it really is that easy. Up in the upper right, click on the ‘contribute’ and I’ve made it even easier. (Don’t worry if it won’t let you pick a category, it’ll go through – and I still have to pick a category for it anyhow. All that does is save it as a draft for me to work on. It certainly doesn’t publish anything without my intervention. That’d just be silly talk!)

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Let’s Learn Some apt Basics

Today we’ll be learning a little about some apt basics. This is only useful if your distro uses apt to manage software. If you aren’t using a distro that does (Debian, Ubuntu, Mint, etc) then this probably isn’t an article that will interest you much, and that’s fine. With the great variety there is in the Linux world, it won’t always be an article that matters to you. Better luck tomorrow! Well, two days from now… 

In the past we’ve covered quite a few apt commands. Here are a few that are poorly formatted ’cause, you know, WordPress…

How To: Clear The apt Cache

Use ‘apt’ To Download A Program And Its Dependencies

Use ‘apt-cache’ To Find An Application’s Homepage

Those are a few – but there are actually more than that. If you’re unfamiliar with apt, you can click any of those articles and learn more about it.

For those of you whose systems use apt to manage packages, this article is for you. If you aren’t aware, apt is the package manager application that you’ll interact with more often than not (if you do things in the terminal).

Apt has a number of commands, of course. As a package manager, it’s bound to be a robust and potentially complicated application. Today, we’ll just be covering a few simple apt commands that you’re most likely to use. It will not be an exhaustive article because of time constraints, reader attention limits, and usefulness. My goal was never to replicate man pages. You’ve still gotta read ’em.

So then, without further ado…

Some apt Basics:

If you want to use apt, you have to have an open terminal. If you don’t know how to open the terminal, you can do so with your keyboard. Press CTRL + ALT + T and your default terminal should open.

With your terminal now open, you can easily install applications with apt. You’ll need to know the package name for the software you want to install, however. So, you can search for packages easily enough:

For example, you can use ‘terminal’ in there as a keyword and get a ton of options, all of which should be installable easily. Again, these are just apt basics.

Now that you know, or you may already have known, the package name, you can install it with:

You don’t need to do the runaround with dpkg for local .deb files, by the way. I’m not sure why people still suggest that? If there’s a good reason for doing it that way, please let me know in the comments. You can just use apt and it works just fine – including resolving dependencies (when they’re able to be resolved). To install a local .deb file with apt:

If you want to get the information for a specific package, you can use the ‘show’ command. That’s easy enough:

If you want to see the dependencies, that is the other applications that need to be installed in order to make it work, then you just check the dependencies with:

If you want to remove a package with apt, then you can just read this article to decide which command is right for your needs:

‘sudo apt remove’ vs ‘sudo apt purge’

That’ll answer it nicely enough.

Closure:

There you have it. You have an article about apt basics, and that’s all it is. You’ll note that not all apt commands need elevated permissions, so there’s no need to use sudo unless you’re adding or removing software. The other commands can be run without elevated permissions.

There’s more to apt. Yes, yes there is. Type man apt and you’ll get an idea of the available options. This article is just some apt basics, the things I think you’re most likely to need on a day to day basis. 

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Let’s Have A Look At The free Command

If the title wasn’t enough, today’s article has us taking a look at the free command. Once again, this will be a nice and easy article. I wanted to write a witty title, but Google doesn’t like witty titles for stuff like this and Google has been mad at me for a couple of months! Either way, it’s a good time for an easy article.

If  you’ve somehow never used the free command, you’re in luck! That’s what this article is going to be about! It should be relatively short, as there’s really only a few ways you’ll want to use the command.

What is the free command? Well, it’s an application that you run in the terminal (like oh so many of my articles) and it gives you some needed information about memory usage. It’s not fine-grained information, it’s about total usage. 

You can get this information all sorts of ways. Both top and htop will happily spit this information out. There are any number of GUI ways to get this information, such as your task and process manager may have a tab to tell you about memory usage. 

Us? No, we’ll be using the free command. The man page happily describes the free command as:

free – Display amount of free and used memory in the system

See? It’s another one of those terminal applications that does exactly what it says it’s going to do! Imagine that!

The Free Command:

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.

You can just run the command with nothing else:

That’s the same as you’d get if you ran free -w, by the way.

You can pick the display units as flags. Just look into man free to learn how to do that, but the easiest output for most people to read will be to display the units in megabytes or in ‘human readable’ form. You do those with:

Or the human-readable format:

Or if you prefer base ten:

Next, as you can see there’s a swap and regular memory section. If you have swap enabled, you can get some small benefit from seeing the total memory used. To do that, try this:

Finally, you can run the command periodically and get a running output so that you can monitor memory usage over time. That one’s pretty simple. The -s means seconds, so the following will refresh every ten seconds:

There’s more that can be done with the free command, so be sure to run man free in the terminal. However, those are the most common ways I use the command, so it’s likely to be fairly similar usage needs for you.

Closure:

There you have it, we have an article about the free command. It’s a good way to monitor memory usage, unless you need something more fine grained. If you want, there are are tools for that – including top and htop. But, those are fine article ideas for another time.

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.

Let’s Reboot Your Linux Computer

Today is another article with one of those things you probably already know, it’s about how you can reboot your Linux computer. Specifically, we’re going to reboot from the terminal. You can use the GUI to reboot easily enough, but if that’s frozen and you don’t really want to do a hard restart, you might as well reboot it if you can.

If you can’t reboot your computer because it appears frozen, consider the Magic SysReq Keys. (More specifically, the REISUB method.)

If you aren’t already aware, there are all sorts of ways to reboot your Linux computer. Like oh so many things in Linux, there’s a multitude of ways. We’re just going to cover a few of them, because you really don’t need to know more. Well, if you do need to know more,  you probably already know those ways to reboot your Linux computer!

It’s also another fairly simple article. That’s good (for me) as it’s a bit like work lately and I don’t want the site to really be about work but rather being about a hobby. If it’s work, I wanna get paid… 

This is also useful information if you’re working on something remote. You don’t want to shut that system down and have to have someone go physically turn it back on, so you reboot the system – making sure to reboot the right system and not the system you’re physically using. I’ve done that more times than I care to share – and I’ve done the reverse as well. It’s seldom good if you enter the reboot command and immediately follow it with a verbal, “Oops.”

Reboot Your Linux Computer:

This article requires an open terminal, because we’ll be learning how to reboot your Linux computer from said 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 now open, let’s start with the easiest of the commands to reboot your Linux computer:

With some distros, that’ll be all you need. With others, you may need to have elevated permissions. This is also often true if you’re connected remotely, via SSH. So, in those instances, you’ll need to preface it with sudo and use your password when asked. Like so:

If you want,  you can also use the shutdown command. That’s pretty easy, you can just use:

The -r flag tells the system to reboot and the ‘now‘ means to do so right now – immediately. You can play around with that ‘now’ bit, like so:

Instead of ‘now‘ you’ll see there’s a ‘1‘ and that’s how many minutes you want to wait before rebooting the system. You can change that to any number you’d like, I suppose.

Finally, you can use systemd to reboot. Why? Because of course you can! It’s systemd, and you can do anything with it! (Kinda like zombo.com, I guess.)

That’ll happily reboot your Linux computer, all nice and neat and proper. It does exactly what you’d expect it to do, so there’s that.

Closure:

There you have it. You now have a few ways to reboot your Linux computer from the terminal. There are other ways, including init or whatnot. You can also just use the GUI if you’re working locally. It’s Linux. There are all sorts of ways to accomplish a given task. That’s a good thing.

I find myself rebooting from the terminal more often than not, simply because I’ve already got a terminal open and it’s just as quick for me to type the reboot command as it is for me to go clicking around. I’m also often testing other systems and really don’t want to have to go fishing around to find the command, then click on some sort of secondary agree menu or the likes.

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