Midnight Commander – the "mc" command – provides an easy way to browse directories and to view, move, delete, compare, change and edit files. Similar in some ways to ranger, mc makes it easy to move around directories and offers side-by-side file/directory listings that work independently of each other. In addition, it provides a very wide range of actions that you can take through simple menu choices.

To start Midnight Commander, simply type "mc" in a terminal window. When you open mc, both the left and right sides of the display will look the same and will show the contents of whatever directory you started in. You can switch sides using the tab key or simply by clicking on a directory or file in the side of the display. You can select a file or directory simply by clicking on it. You can also browse directory contents using the up and down arrow keys.

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There are quite a few changes you can make to user accounts on Linux systems: setting them up, deleting or disabling them, adding or removing users from secondary groups, changing usernames or UIDs, moving home directories, changing users’ shells, altering account expiration timing, and so on.

One command that can make nearly all of these changes easier is usermod. The only real constraints are 1) that the accounts you intend to change must already exist on the system (this command won’t set them up from scratch), and 2) that the affected users should probably not be logged in when you make these changes.

The basic syntax for the command is usermod [options] LOGIN but that options section has a lot more possibilities than you might anticipate. In addition, sudo permissions will be required for this command since superuser access is required to set up or change nearly all user account settings.

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When you want a process to continue running even after you log off a Linux system, you have a couple options.

One of them is to use the disown command. It tells your shell to refrain from sending a HUP (hangup) signal to the process when you log off. So, the process continues running. This can be very handy whenever you start a process and then, for some reason, you can’t stay logged in and wait until it finishes.

The disown command is a shell built-in. This means that you don’t have to install it to use it, but it also means that it won’t be available if you use a shell that doesn’t support it. For those of us using bash and related shells (zsh, ksh etc.), disown should be available and you can verify this with a command like this that lists shell built-ins and then looks for "disown":

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Deploying password-quality checking on your Debian-based Linux servers can help ensure that your users assign reasonably secure passwords to their accounts, but the settings themselves can be a bit misleading.

For example, setting a minimum password length of 12 characters does not necessarily mean that all your users' passwords will actually have 12 or more characters.

Let's stroll down Complexity Boulevard and see how the settings work and examine some that are worth considering.

The files that contain the settings we're going to look at will be:

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Who would have imagined that there’s a Linux tool available for downloading YouTube videos? Well, there is and it works for Linux as well as for other operating systems. So, if you need to watch some of the available videos even when your internet connection is flaky or you need to be offline for a while, this tool can be especially handy.

The tool for downloading videos is called youtube-dl. (The “dl” portion undoubtedly means “download”.) It’s very easy to use and drops webm or mp4 files onto your system. Both formats provide compressed, high-quality video files that you can watch whenever you like.

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Ranger is a unique and very handy file system navigator that allows you to move around in your Linux file system, go in and out of subdirectories, view text-file contents and even make changes to files without leaving the tool.

It runs in a terminal window and lets you navigate by pressing arrow keys. It provides a multi-level file display that makes it easy to see where you are, move around the file system and select particular files.

To install ranger, use your standard install command (e.g., sudo apt install ranger). To start it, simply type “ranger”. It comes with a lengthy, very detailed man page, but getting started with ranger is very simple.

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When you delete a file on a Linux system, it isn’t necessarily gone forever, especially if you just recently deleted it.

Unless you rubbed it out with a tool such as shred, the data will still be sitting on your disk—and one of the best tools for recovering deleted files, testdisk, can help you rescue it. While testdisk has a wide range of functionality including recovering lost or damaged partitions and making non-booting disks bootable again, it’s also frequently used to restore files that were deleted by mistake.

In this post, we’ll take a look at how you can recover deleted files using testdisk and what each step in the process looks like. Since the process requires quite a few steps, you’re likely to feel more comfortable running through them once you’ve done it a few times.

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While far from being one of the first 50 Linux commands anyone learns, the lshw command (read as “ls hardware”) can provide a lot of useful details on your system’s hardware.

It extracts details—maybe quite a few more than you knew were available—in a format that is reasonably easy to digest. Given descriptions, logical (device) names, sizes, etc., you are likely to appreciate how much detail you can access.

This post examines the information that lshw provides with a particular focus on disk and related hardware. Here is some sample lshw output:

$ sudo lshw -C disk *-disk:0 description: SCSI Disk product: Card Reader-1 vendor: JIE LI physical id: 0.0.0 bus info: scsi@4:0.0.0 logical name: /dev/sdc version: 1.00 capabilities: removable configuration: logicalsectorsize=512 sectorsize=512 *-medium physical id: 0 logical name: /dev/sdc 

Note that you should run the lshw command with sudo to ensure that you get all of the available details.

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If you haven’t tried it yet, you might be surprised by the many features of shopt. While it works like a Linux command, it’s actually a bash shell builtin that allows you to change many things about that shell’s behavior.

One option, for example, allows the shell to fix minor typos when you type directory names. To demonstrate, in the first cd command shown below, the directory name, bin, is typed with an extra letter and the shell complains and gives up:

$ cd binn -bash: cd: binn: No such file or directory 

This next command enables the cdspell option that gets bash to attempt to correct minor typos in directory names.

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The stat command supplies a lot of detailed information on files.

It provides not just the date/time of the most recent file changes, but also shows when files were most recently accessed and permissions changed. It tells you the file size in both bytes and blocks. It displays the inode being used by the file along with the file type. It includes the file owner and the associated user group both by name and UID/GID. It displays file permissions in both the “rwx” (referred to as the “human-readable” format) and numerically. On some systems, it might even include the date and time that a file was created (called its “birth”).

In addition to providing all this information, the stat command can also be used to create file listings. These listings are extremely flexible in that you can choose to include any or all of the information described above.

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Want to get work done a little faster, spend less time remembering commands and maybe even show your coworkers how clever you are? Easy. Set up several dozen bash aliases.

Your days will get easier and a tad less stressful. You might even have some fun. In this post, we'll look at the various types of aliases that you can set up, and what you need to know to manage them.

Why use aliases?

Using aliases helps you to avoid having to type a lot of command details, especially those that are hard to remember or require a lengthy string of options that might have to be entered in some particular order before they'll spit out just the output that you're waiting to see.

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There are many ways to list files and display information about them on Linux systems. This post reviews a number of commands that provide details on files and provides options for customizing your file listings to meet your needs.

Most of the commands list files within individual directories while others reach as deeply into a file system as you care to look.

The primary command for listing files is, of course, ls. This command, however, has an extensive number of options for finding and listing just the files you want to see. Plus, there's always find for helping with very specific file searches.

Listing files by name

The easiest way to list files by name is simply to list them using the ls command. Listing files by name (alphanumeric order) is, after all, the default. You can choose the ls (no details) or ls -l (lots of details) to determine your view.

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Process accounting is a method of recording and summarizing commands and processes. It's an option on Linux systems, but you have to enable it and use a particular command to view the details collected. This post covers the commands involved and offers some suggestions on making the views even more useful.

To start, understand that process accounting is different than what you see when running the ps command. It shows details on commands that have completed –- not those that are currently running. It also shows a lot more details than you would see by looking at your users' command history files and keeps all the collected data in a single file on the system.

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In these stressful times, one way to distract ourselves from the gloom is by playing word games. With this thought in mind, I challenged myself to identify words that, spelled backwards, would still be words.

Instead of cheating by doing a simple Google search, I cheated by using my Linux commands skills. So, in this post, we’ll look at how Linux commands and resources can be used to identify such words.

Defining the search

Before we get started on the Linux search technique, I should point out that what I was looking for were not just palindromes – words like “civic” and “deified” that read the same from left to right as they do right to left. Instead, I was also looking for words like “reward” and “decaf” that turn into different words – in this case, “drawer” and “faced” -- when one reads them backwards.

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There are a number of ways to merge and sort text files on Linux, but how to go about it depends on what you're trying to accomplish – whether you simply want to put the content of multiple files into one big file, or organize it in some way that makes it easier to use. In this post, we'll look at some commands for sorting and merging file contents and focus on how the results differ.

Using cat

If all you want to do is pull a group of files together into a single file, the cat command is an easy choice. All you have to do is type "cat" and then list the files on the command line in the order in which you want them included in the merged file. Redirect the output of the command to the file you want to create. If a file with the specified name already exists, it will be overwritten by the one you are creating. For example:

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In addition to all its other successes, Linux dominates supercomputing: All 500 of the worlds fastest supercomputers run Linux, and that has been the case since November 2017, according to the TOP500 organization, which has been ranking the 500 most powerful computer systems since 1993. (A graph of Linux' ascension is available on here.)

How did this happen?

A little history

Linux began life in 1991 as the personal project of 21-year-old Finnish student Linus Torvalds. I first became aware of it several years later while working at Johns Hopkins University’s physics and astronomy department where I managed the department’s network and a number of servers with the help of a couple grad students.

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Dig is a powerful and flexible tool for interrogating DNS name servers. It performs DNS lookups and displays the answers that are returned from the name servers that were involved in the process along with details related to the search. System and DNS administrators often use dig to help troubleshoot DNS problems. In this post, we’ll take a deep dive into how it works and see what it can tell us.

To get started, it's helpful to have a good mental image of how DNS or domain name system works. It's a critical part of the global Internet because it provides a way to look up and, thereby, connect with servers around the world. You can think of it as the Internet's address book and any system that is properly connected to the Internet should be able to use it to look up the IP address of any properly registered server.

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Getting a summary of the commands you use on a Linux system requires only a relatively modest string of commands along with a couple pipes to tie them all together. When your history buffer preserves the most recent 1,000 or 2,000 commands, summarizing command activity can get rather tedious. This post provides a handy way to summarize command usage and highlight those commands used most frequently.

To start, keep in mind that a typical entry in a command history might look like this. Note that command is displayed after the command sequence number and followed by its arguments.

 91 sudo apt-get install ccrypt ^ +-- command 

Note that the history command, adhering to the HISTSIZE setting, will determine how many commands will be preserved. This could be 500, 1,000 or more. If you don't like how many commands are preserved for you, you can add or change the HISTSIZE setting in your .bashrc or other start-up file.

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There are numerous commands for encrypting files on Linux. When you want to limit access to file contents, you can use file permissions but file encryption makes limiting access much more effective. This post compares some of the commands for encrypting files and provides an easy script for trying them out.

Encryption means, of course, that a file that you can look at with Linux commands and tools is altered in ways that make it unusable and unreadable unless you reverse the encryption process. Encryption does not generally reduce the size of files unless compression is used as well. In fact, the encryption process might make some files larger. Some commands compress by default; others do not.

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There’s a lot more to identifying a Linux release than citing a simple version number. Even a quick look at the output from the uname command can tell you that. What is all of that information, and what does it tell you?

In this post, we’ll take a closer look at the output from the uname command along with release descriptions provided by some other commands and files.

Using uname

A lot of information is displayed whenever you issue the command uname -a in a Linux system terminal window. That's because that little “a” tells the man command that you want to see all of the output that the command is able to provide. The resultant display will tell you a lot of different things about the system. In fact, each chunk of information displayed tells you something different about the system.

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Extracting files from archives in Linux systems is considerably less painful than tooth extraction, but sometimes seems more complicated. In this post, we will take a look at how you can easily extract files from just about any kind of archive you’re likely to run into on a Linux system.

There’s a pile of them – everything from .gz to .tbz2 files with some variations for how those files are named. Sure, you can memorize all of the various commands available for extracting files from archives along with the options they offer, but you can also just deposit all that know-how into a script and stop worrying about the details.

In this post, we assemble a series of extraction commands into a script that calls the proper command to extract the content of file archives depending on the archive file names. The script starts with some commands to verify that a file name has been provided as an argument or ask that the person running the script provide one.

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Why would you ever want to stress your Linux system? Because sometimes you might want to know how a system will behave when it’s under a lot of pressure due to a large number of running processes, heavy network traffic, excessive memory use and so on.  This kind of testing can help to ensure that a system is ready to "go public".

If you need to predict how long applications might take to respond and what, if any, processes might fail or run slowly under a heavy load, doing the stress testing up front can be a very good idea.

Fortunately for those who need to be able to predict how a Linux system will react under stress, there are some helpful techniques you can employ and tools that you can use to make the process easier. In this post, we examine a few options.

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If you’re managing a Linux server, it’s good to be ready with a number of commands that you can use to check user activity – when your users are logging in and how often, what groups they belong to, how much disk space they’re consuming, what command they're running, how much disk space they're occupying, if they’re reading their mail and more.

In this post, we'll look at a number of commands that can help you understand who your user are and how they work.

finger

One handy command for getting a user profile is finger. It allows you to see who is logged in or focus on a single user to view their last login, where they logged in from, how long they've been idle (how long since they ran a command), etc. In this command, we are looking at the user nemo.

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There are a number of ways to loop forever (or until you decide to stop) on Linux and you can do this on the command line or within scripts.

The for and while commands make the job quite easy. There are only a few things to keep in mind with respect to syntax and tactics.

Using while

One of the easiest forever-loops involves using the while command followed by the condition "true". You don’t have to bother with logic like while [ 1 -eq 1 ] or similar tests. The while true test means the loop will run until you stop it with CTRL-C, close the terminal window or log out. Here's an example:

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Linux provides many commands for examining the contents of files including cat, more, head and tail, but that's just a start.

For one thing, even the most obvious commands have a lot more options than many Linux users ever get around to using. And there are some less obvious commands that offer some unique features. In this post, we’ll both at commands for viewing the contents of files and options for tailoring those views to better cater to your needs.

cat

The cat command sends the entire contents of text files to your terminal window for viewing. In fact, if you type “cat” followed by the name of a file with thousands of lines, those lines will whiz by your window so fast, you won’t be able to make out much more of it than the last screenful of text. Yet, as familiar as the cat command is to Linux users, even this basic command provides a lot of useful options such as numbering the lines in the output that many of us likely haven’t ever used. To expand on that, not only can you number lines; you have some choices in how you do the numbering.

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Symbolic links play a very useful role on Linux systems. They can help you remember where important files are located on a system, make it easier for you to access those files and save you a good amount of disk space and trouble by making it unnecessary for you to copy large files just to make them a little more accessible.

What exactly is a symbolic link?

Generally referred to as a "symlink" or "soft link", symbolic links are very small files. In fact, all a symlink really contains is the name of whatever file it points to, generally along with the file system path (relative to the current location or absolute). If a file named ref1 points to a file named /apps/refs/ref-2020, ref1 will be 19 characters long even if the ref-2020 file is 2 terabytes. If it points to ./ref-2020, it will be only 10 characters in length. If it points to ref-2020, only eight.

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The tmux tool is one of a number of Linux terminal window splitters that allow you to run commands in adjacent (up/down, right/left or both) panes so that you can easily use the output in one pane to help with work you’re doing in another. You can even disconnect a multi-pane tmux session and reattach to it when you need it again.

What's more, processes running within tmux will continue running even when you detach, making tmux an excellent tool to use when you’re not sure your connection to a remote server is solid and don't want to be dropped in the middle of an important task.

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Believe it or not, it's possible to open a Linux terminal on a Windows 10 system and you might be surprised how much Linux functionality you’ll be able to get by doing so.

You can run Linux commands, traipse around the provided Linux file system and even take a novel look at Windows files. The experience isn’t altogether different than opening a terminal window on a Linux desktop, with a few interesting exceptions.

What is needed to make this happen is something called the Windows Subsystem for Linux (WSL) and a Windows 10 x86 PC.

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There are quite a number of ways to look at running processes on Linux systems – to see what’s running, the resources that processes are using, how the system is affected by the load and how memory is being used. Each command gives you a different view, and the range of details is considerable. In this post, we’ll run through a series of commands that can help you view process details in a number of different ways.

ps

While the ps command is the most obvious command for examining processes, the arguments that you use when running ps will make a big difference in how much information will be provided. With no arguments, ps will only show processes associated with your current login session. Add a -u and you'll see extended details.

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If you want to run a command on a Linux system until it succeeds, there are some really easy ways to do it that don’t require you to retype the command repeatedly or sit in front of your screen pressing !! (repeat the previous command) until the command works. In this post, we’ll look at two options available with bash.

Using while !

First, we’ll look at an easy example of trying to display the contents of a file. This trick is to use the bash while command to create a loop, but preface the command that you want to run with a ! sign so that it loops until the command succceeds. Here’s how it works.

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