Tag: file permissions

Disallow Directory Listing (in the terminal)

In today’s article, and for no apparent reason, we’re going to learn how to disallow directory listing in the terminal. This seems like a good article for beginners to learn, and it seems like something most folks might like to know. So, if you want to disallow directory listing read on!

You never know when you might want some additional privacy, though I’d definitely not confuse this for strong privacy measures like encryption, amongst your files. Perhaps you’re planning on releasing a memo and you don’t want anyone to read it until you’re done?

I dunno? It’s up to you as to why you’d want the potential privacy from making it so that the files in a directory can’t be listed. Your reasons are your own. I just share tidbits of knowledge.

We will be using ‘chmod’ in this exercise. The man page for ‘chmod’ describes itself like:

chmod – change file mode bits

But, for our purposes and generally speaking, it’s used to adjust the file permissions. As you should know, files have various permissions in Linux – and everything in Linux is a file. There are read, write, and executable bits that can be set (with said chmod, for example) and there’s also file ownership (for another day). We’ll be using those permissions to prevent listing the files in a directory.

Ready? It really won’t take long – and it should be easy enough for anyone…

Disallow Directory Listing:

As the title suggests, this is another ‘in the terminal’ application. So, of course, you’ll need an open terminal. You should open a terminal now. 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 first start by making a directory – just so that we can then use that to disallow directory listing. We’ll just do this in your /home directory. Start with:

Now, let’s move to the new ‘sample’ directory and make a couple of files.

Now, what we’re going to do is change the permissions of the ‘sample’ directory, like so:

You don’t need ‘sudo’ or anything, because these files belong to you. But, you can now test it. While still in the folder, try any of the following:

Or (from outside the directory, if you’d like):

In all cases, it should give you a ‘permission denied’ error, because you no longer have permission to list files from within that directory.

If you wish to reverse this, you can simply try changing the permissions again. You can just:

With that command, you can resume directory listing. So, it’s pretty easy to reverse the process. It’s also not the greatest security measure you can take, because of that. So, do what you will with it, as you now know how to disallow directory listing in the terminal.

Closure:

There you have it, it’s yet another article. This one seemed like an interesting one to write, so I figured I’d write it. You never know when you want to disallow directory listing, but now you know how to do so. If you have any questions, feel free to ask…

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How To: Find Files Owned By A Specific User

In today’s article, we’ll be learning how to find files owned by a specific user. We’ll even use the ‘find’ command, as we find files owned by a specific user! That seems to be the best idea, and the best way to do it.

This should also be a fairly quick article. I don’t see any reason why I’d have to make it longer than it needs to be. So, it won’t take too much of your time today.

This article will be published on November 11. That’s a day known by a number of other names. It’s Veteran’s Day, Armistice Day, Remembrance Day, and probably a dozen more names that I don’t know. It was the day WWI ended, which was thought to be the war to end all wars ’cause it was just that horrific.

Well, as you can see, it was definitely not the last war – but we still choose this day to remember. In the US, veterans are celebrated today. Memorial Day is only for those who are no longer with us. Today is for the vets, as well as those who are no longer here.

It’s a holiday, which means it’s a fine day to have a nice and simple article. It’s a fine day to cherish your friends and family, instead of spending your time online reading Linux articles. (But thanks for doing so!)

Find Files Owned By A Specific User:

This article requires an open terminal, like so very many other articles. 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, you should probably navigate to a directory other than your home directory. If you run this command in your home directory, it’s gonna output a whole lot of text. So, let’s just try this first in your ~/Downloads directory:

The command we’re going to use is find, and the format is the find command, a dot to say the current directory, the -user flag, and then the username. So, your command would look something like:

(No brackets, of course.)

You probably don’t have any files owned by root in that directory, so a good test to make sure it’s working properly would be something like:

Now, you can mix things up a bit. Instead of using the dot to indicate the current directory, let’s find files owned by root in the /etc directory.

See? That’s not all that hard at all. It’s remarkably easy to find files owned by a specific user – and the command really isn’t that hard to memorize! You can run it in the folder you’re in, or you can use the directory path method.

Closure:

I told you that it’d be a quick article today. It’s a good day for just a quick tip and everyone can benefit from knowing how to find files owned by a specific user. Toss this tip into your growing list of tools in your Linux toolbox, because  you never know when this will come in handy.

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How To: Make A File Executable

Today we’re going to learn something important, that is how to make a file executable. This is something everyone should know how to do. It’s not going to be easy to make this into an article, ’cause it’s really quite easy, but I’ll give it a shot.

One of the important things about Linux is that files have various permissions. You can read, write, and execute a file based on the permissions. This helps keep Linux a bit more secure, because files can’t be executed until you’ve given them permission to do so.

I’ll make this article as straightforward as I can, by trying to give you an example of how this works. We’ll create a file, make it executable, and then run said file. This should serve as a good example, so that you can do so in the future.

You’ll see a bunch of commands in this article. If you’re new, just follow ’em until the end and you’ll hopefully understand what’s going on, and see how to make a file executable. Trust me, this isn’t something all that taxing. I’m sure you can get it!

Make A File Executable:

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 create a new file. We’ll do that with:

Open love.sh for editing with nano by using the following command:

Enter the following text:

Now, you’ll have to save that. Just press CTRL + X, then Y, and then ENTER. That will save the file with the newly added text.

Now, we’ll make the file executable with the ‘chmod‘ command. That’s done with this command:

With that done, all you need to do now is execute the file. To do that, you just call the file by name in the terminal. As you’re still in the same directory, you’ll need to use ./ – so your command actually looks like:

With that, you should get a message saying that you love Linux Tips. Aww… Isn’t that sweet of you! We love you too! It was also a fun way to create a file, edit it, make it executable, and then actually executed said file.

Closure:

See? That wasn’t all that hard. I hope that method shows you a little about how to make a file executable. It’s a pretty basic skill that all Linux users should be familiar with. It’s not a very complicated article, but that’s just fine. At least we (hopefully) had some fun with it.

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Change Ownership Of Files And Folders

Today, we’ll be covering how to change ownership of files and folders. This is a pretty basic task and one every Linux user should know. This needn’t be terribly complicated, so this article will explain all you really need to know about changing ownership of files and folders.

When dealing with file management, permissions are important. It’s a security matter and a usability matter. You can assign various file and folder permissions, such as read and write permissions, a subject for a different article. However, files and folders all should have owners – owners who can do anything they want with the file or folder.

Curiously, your account should not always be the owner. While maybe not all that intuitive, you shouldn’t have ownership of all the files. This is why you have to use elevated permissions to perform certain tasks. This is to keep things segmented and secure.

Remember, Linux is designed to be a multi-user operating system. That’s not just human users, but different processes and applications may also be associated with users. For example, look at all the users on your system by running the following command in your terminal emulator:

You can also see all the groups on your system with this command:

Obviously, if a user is a member of a group they share permissions with that group. Files also only have one owner and one associated group, of course. So, if you want two people to have control over a file, one way to do that would be to make sure they’re both members of the same group. There’s all sorts of creative things you can do with permissions. This article will be covering just one aspect, it’ll be about how you can …

Change Ownership Of Files And Folders:

Like oh so many of these articles, this one requires an open terminal. You can do so using only your keyboard – just press CTRL + ALT + T and your default terminal should open.

Go right ahead and stay in your home directory. You can check the various files and their permissions with the following:

The output of that command will show you the user and group, with the two being listed in that order as in the image below:

ll listing user and groups
See? I even gave you handy arrows. The order is owner:group, to repeat myself.

To change the owner, the format is:

To change the group, the format is:

If you want to recursively take ownership, you need the -R flag. For that, you’d want something that looks a bit like this:

You can actually just use chown to change both the owner and group at the same time. You’ll most often do this with your own user and group, so I’ll show the command that way:

As you can guess, the -R flag will work there and an asterisk will cover all the files and folders within that directory. Obviously, this applies to folders and not to files.

Closure:

There you have it. You have yet another article and this one has hopefully taught you how to change ownership of files and folders. It may not be one of the most interesting articles, but it’s a skill you’ll eventually want to have and another tool for your Linux toolbox. 

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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