KVM with Barrier: Control multiple computers with a single keyboard and mouse

Control multiple computers with a single keyboard and mouse It's no longer exclusive to old physical KVM switches. Thanks to tools like Barrier, you can have several computers on your desk, with different operating systems, and manage them as if they were a single unit, without touching a single cable.

In this article we will see What is Barrier, and how does it work as a software KVM?This article will cover its limitations, the systems it can be used on, and what to do when something goes wrong, such as the typical SSL certificate error or connection problems between Linux and macOS. The goal is that, by the time you finish reading, you'll have a clear understanding of how to get the most out of Barrier on your local network.

What is Barrier and why is it considered a software KVM?

When we talk about traditional KVM, we are referring to a physical device that allows share keyboard, video and mouse (Keyboard, Video, Mouse) between several computers. These gadgets connected to the computers via cables, and you switched between machines by pressing a button or turning a wheel. Convenient for its time, but a bit outdated nowadays.

Barrier performs exactly that function, but everything is managed by software. That is to say, You don't need any physical device.Simply install the application on all the computers you want to control, configure one as the server (the one with the physical keyboard and mouse), and the rest as clients. From then on, by moving the mouse to the edge of the screen or using a special key, you can switch between computers.

Barrier's philosophy is clear: Maintain the simplicity of the old Synergy 1.xWithout unnecessary frills or complications, its aim is to make you forget you're using multiple computers and give you the feeling of being in front of a giant extended desktop, even though there are different machines and systems underneath.

Historically, Synergy was the project that popularized this software-based KVM concept. Later, Synergy was commercialized and evolved with new features, while Barrier was born as a fork of the Synergy 1.9 codebase to maintain a free, open, and simplicity-focused alternative. Synergy, in turn, was a reimplementation of CosmoSynergy, originally created by Chris Schoeneman.

It is worth noting that, as of today, Barrier and Synergy are not compatible with each other.If you want to share a keyboard and mouse between several computers, they must all have Barrier (and a reasonably recent version) installed for communication to work correctly.

Key features of Barrier such as “KVM with Barrier”

The main appeal of Barrier is that it... It allows you to manage multiple computers from a single workstation. without having to change USB ports or fiddle with cables. This translates into several practical advantages, especially if you work with more than one operating system at the same time.

One of the pillars of the tool is the cross-platform compatibilityBarrier works on Windows (7, 8, 8.1, 10, and 11), macOS (with some limitations we'll discuss), Linux, FreeBSD, and even OpenBSD. The idea is that if you have, for example, a Windows desktop, a Linux laptop, and a Mac, you can control them all effortlessly with a single keyboard and mouse.

Another practical function is the clipboard sharing between computers. With Barrier, you can copy text on one computer and paste it on another, as if they were all in the same work environment. While compatibility with different languages ​​and character sets isn't perfect (there are reports of problems with UTF-8 and some alphabets), for normal use with Latin text it usually works reasonably well.

In terms of usability, the tool focuses on offering Reliability without headachesThe developers are regular users of the program and set out to solve Synergy's recurring problems, iron out bugs, and share those improvements with the community. No flashy effects or super-advanced features: the goal is for you to install it, configure it once, and forget about it.

Communication with users is another important point. The project is managed openly: Everything goes through the repository and the incident system.where you can see if anyone else has reported the same issue, provide details, track the progress, and see when it will be resolved. They also have a chat channel on the LiberaChat network, in the channel #barrierfor quick questions or just to say hello.

Barrier compatibility with operating systems and versions

One of the strengths of using Barrier as a software KVM is that It doesn't tie you to a single systemIf you work in mixed environments, you'll notice a significant difference compared to a classic physical KVM. However, there are important nuances depending on the platform and operating system version.

On Windows, compatibility is fairly straightforward: Barrier works on Windows 7, 8, 8.1, 10 and 11provided you're using a modern version of the tool. However, 32-bit versions are not supported; the focus is on 64-bit systems, which are the current standard.

In the Apple ecosystem, things are a bit more complicated. Barrier works in macOS (formerly OS X / Mac OS X)However, the current graphical interface is not compatible with versions earlier than macOS 10.12 Sierra. This is because the GUI relies on Apple's Metal framework, which is not available in older versions of the system. On machines running OS X 10.10 Yosemite or Mac OS X 10.9 Mavericks (and possibly earlier), the command-line portions of Barrier should, in principle, start without issue, but The graphical interface does not run. because the system lacks Metal.

Barrier is very widespread in Linux. In fact, Many distributions already include pre-packaged goods. Barrier is available in their repositories, so you can install it without compiling anything. Flatpak and Snap packages are also available if you prefer more universal formats. To see a fairly comprehensive list of distributions that include Barrier, you can usually use services like Repology, which displays the packages available in different repositories.

In the field of BSD-type systems, Barrier also provides support to FreeBSD and OpenBSDAlthough package availability and the installation process may vary slightly, the intention of the project is that, if you work with one of these systems, you can integrate them into your "KVM with Barrier" without major complications.

It should also be noted that the project can only provide official support for Barrier versions from 2.3.4 onwardsIf you're using an older build, we recommend updating as soon as possible, as security vulnerabilities and other bugs have been fixed. This is especially important if any of your devices are accessible from the internet or frequently connect to shared or unreliable networks, such as public Wi-Fi.

Barrier installation on the various equipment

To set up your own “KVM with Barrier”, the first step is install the program on all involved computersUnlike a hardware KVM, there's no need to plug in anything unusual: everything is done over the network, usually over your home or office LAN.

In most modern Linux distributions, you'll find Barrier directly in the repositories. In that case, simply use your usual package manager. If you prefer a more portable format, Flatpak and Snap packages are also available. These builds are maintained on platforms like Flathub and Canonical's repositories. They are typically generated automatically using continuous integration systems, such as Azure Pipelines, which help ensure that versions are built consistently.

On Windows and macOS, the development team publishes versions ready for downloadSo you just need to install the corresponding executable or package. Many users find that their distribution or system already has Barrier packaged or available, but if that's not the case for you, you can always use the official releases.

The key is that Barrier must be present in all the equipment you're going to handleThis applies both to the server (the one with the physical keyboard and mouse) and to the clients (the other machines to be controlled). It's not enough to have it on just one device, because communication takes place directly between the Barrier instances on each device.

Once installed, you'll see that the application has a simple graphical interface for defining who is the server, who are the clients, and how the screens are arranged. From there, you can also access advanced options, such as encryption settings, the communication port, and mouse and keyboard behavior when switching between computers.

Basic configuration of Barrier as a server and client

The most common way to use Barrier as a software KVM is choose a main computer to act as the serverThis is usually the computer you're sitting at, with your keyboard and mouse connected. The other machines will be clients that accept commands from the server.

The general procedure is simple: first you run Barrier on all machines. On the computer with the physical keyboard and mouse, select server mode.In some cases, you select client mode, while in others you choose client mode. On the server interface, you'll see a "Configure server" button that takes you to a grid where you can place representations of the client screens.

In that grid, you drag a new "screen" for each client you're going to use. You must assign a [missing information] to each screen. screen name that exactly matches This is the IP address that appears in each client's Barrier window, just above the server's IP address. It's important to respect uppercase letters, lowercase letters, and any other characters, as the match is case-sensitive and makes it difficult to type.

For clients, you only need to indicate the IP address of the server and the port that Barrier will use (by default, it's usually 24799). In some environments, the application may use Bonjour or other auto-configuration mechanisms to detect the server, but if that doesn't work, you can always enter the IP address manually. Once you've completed these steps, you should be able to click "Start" on both the server and clients and see the connections being established.

If everything goes well, in the log windows on both sides you will see messages indicating that Barrier is running and the connection is activeFrom that point on, you can move the mouse to the edge of the server screen, and when you cross that boundary, the cursor will appear on the adjacent client screen. Similarly, the keyboard will type on the machine to which the focus has "shifted."

One detail that goes unnoticed by many users is that, if The Scroll Lock key is activated on the keyboardThe Barrier key blocks mouse movement between screens. It's a sort of "safety" to prevent accidental focus changes. If you suddenly find yourself unable to switch between computers, check out that key before you mess around with the settings.

Configuration management and automatic startup

Once you have your “KVM with Barrier” tuned, it's quite comfortable save the settings and reuse them Instead of reconfiguring everything every time you open the application, Barrier does it almost automatically, but it's still useful to know where it stores things.

In Linux, after configuring the server from the graphical interface, the application generates a configuration file in the path $HOME/.local/share/barrier/.barrier.confThis file stores screen layout data, hostnames, network options, and other settings. You can close the graphical interface and Launch the Barrier server from the command lineThis will read the configuration file and apply the options exactly as you left them in the GUI.

If you want Barrier to automatically load a specific configuration on startup, you can start the binary with the parameter –config followed by the path to the fileSomething like barrier --config <ruta_al_config> This will cause the application to directly launch the server or client with that screen layout, without needing to tweak the interface each time.

In some cases, users find that when uploading a configuration file to the client, The “Server IP” field is shown as emptyIf this happens to you, the solution involves manually editing the configuration file and ensuring it includes the correct server IP address. It's not enough to rely on the GUI to fill it in automatically; if an old or incomplete configuration was imported, you'll likely have to correct it manually.

This text file-based approach has the advantage that You can version and copy your settings easily between machines, or even integrate Barrier startup into more complex startup scripts, for example in laboratory environments, classrooms or scenarios with many computers connected by the same "KVM with Barrier".

Barrier's current limitations and outstanding issues

Although Barrier is very useful for setting up a software KVM, it's important to keep in mind certain technical limitations of the current versionIgnoring them can lead to frustration if you're expecting features that don't yet exist or are simply not supported on your platform.

One of the most talked about is the absence of drag and drop in LinuxIn other words, you can't simply drag and drop a file on one Linux machine onto another to transfer it directly via Barrier. This functionality isn't currently implemented, and if you'd like to follow its development or contribute, the repository references a specific issue where this is discussed.

Another somewhat delicate aspect is the Unicode text management and special charactersThere are reports of problems with certain languages ​​and character sets when sharing the clipboard between machines, especially when different operating systems are used. This doesn't mean it will always fail, but compatibility isn't perfect, and you might encounter some issues in certain situations.

In the Linux ecosystem, many users ask about the support for WaylandWayland, the modern replacement for the classic X11 graphics server. For now, the project acknowledges the interest and is keeping a close eye on Wayland's evolution, but there is no firm date for full support. Some reports emphasize that, as of the end of 2021, a definitive integration was not expected, and those with expertise are encouraged to contribute through open issues related to Wayland.

In addition to these functional limitations, there is the fact that, as with any live software project, There is a list of errors and pending tasks which is managed in the "Issues" tab of the repository. There you can see what's broken, what's being improved, and in which areas the developers are requesting more help, whether in the form of detailed bug reports or ready-to-review patches.

Support, community, and collaborative development

Barrier operates with a very open philosophy: Everything is discussed and recorded publiclyFrom the smallest incidents to the most important design decisions, this has the advantage that any user can check the issue tracker to see if their problem has already happened to someone else or if a solution is in progress.

If you want to report a bug, the team insists that the The only official way to get their attention is to create a new incident report. In the issue manager, explain the problem clearly, concisely, and in detail, including the Barrier version, operating system, relevant log messages, and steps to reproduce the error. The better described the issue, the more likely you are to receive an equally clear and helpful response.

Regarding priority, developers usually give priority to problems that affect more usersThat doesn't mean individual cases are ignored, but rather that the focus is first on what breaks the experience for a large group of people, whether it's a major incompatibility or a security flaw.

For quick inquiries, minor doubts, or simply to share impressions, the community usually gathers in the #barrier channel of the LiberaChat IRC networkIt's not a substitute for the incident reporting system, but it's very useful if you want to resolve a small doubt, check if strange behavior is happening to someone else at that moment, or even coordinate efforts to debug a complex problem.

The project is also open to code contributions. If you find a bug and are willing to fix it yourself, you can send a pull request with your patchMost change requests must be accompanied by a release note, following the guidelines explained in the internal documentation (for example, in the README file corresponding to the change releases or snippets). Once the PR is submitted, the maintainers will review it and, if everything is in order, merge it into the main code.

Practical example: connection problems between Linux Mint and macOS

In practice, one of the most typical scenarios in which Barrier is used as a software KVM is Sharing keyboard and mouse between a Linux desktop and a MacImagine the case of someone who has a laptop with Linux Mint acting as a server and a Mac Mini with macOS Mojave as a client.

Let's assume that a recent version of Barrier (for example, 2.4.0 with a specific build date) is installed on the Mac Mini and has been configured in client mode, even disabling the firewall for applications like Little Snitch to avoid network blocks. The Mac and the laptop running Linux Mint are connected via Ethernet cable to the same router; that is, They share the same local network.

On the Linux Mint side, the same version of Barrier is also installed, but configured as a server. The distribution's firewall is disabled, it's verified that both programs display the same IP address and port (24799 by default), and it's checked in the server configuration panel that both "blue screens" have the correct hostnames. At first glance, everything appears to be configured correctly.

However, the following message appears in the Barrier registration window in Linux Mint: “ERROR ssl certificate doesn't exist”On the Mac Mini, lines like “NOTE: connecting to '192.168.1.15': 192.168.1.15:24799” followed by “NOTE: disconnected from server” are displayed. In other words, the client attempts to connect, manages to open the channel, but the connection is lost shortly afterward.

This type of situation usually indicates that, although basic network connectivity is correct, The server does not have a generated or accessible SSL certificate.And therefore the encryption layer fails. In many cases, regenerating the certificate from Barrier's options, checking the file permissions, or deleting the configuration to create a new one can resolve the issue. It's also advisable to ensure there are no traces of an old installation that used different parameters or whose path has changed.

As you can see, even when everything appears to be properly aligned (same version, same network, firewall disabled, matching IP and port), small details such as the certificate or legacy configuration These issues can cause disconnections. In these cases, in addition to reviewing the logs and searching for the specific error in the project's incident management system, it's a good idea to check the community chat channel to see if anyone else has experienced the same problem and how they resolved it.

Barrier versus a traditional hardware KVM

When you compare a hardware KVM with a “KVM with Barrier”, there are several points where The software approach offers clear advantagesTo begin with, you save yourself the tangle of video cables, USB cables and other connectors that physical devices require, as well as the limit of ports they support.

With Barrier, as long as the devices are connected to the same local network (or, if you set it up more carefully, even through a secure VPN), no matter where they are physicallyYou can have the server on your desktop, a Linux machine in a rack, and a Mac in another room, and still control them with the same keyboard and mouse without moving from your spot.

Furthermore, since it is free and cross-platform software, You don't depend on the physical KVM supporting a specific video standard. Nor does it care whether or not it has the correct connector (HDMI, DisplayPort, etc.). Barrier simply manages keyboard, mouse, and clipboard input; the video is displayed on the monitors connected to each machine as usual, and you simply "jump" between them.

Of course, there are also situations where a physical KVM still makes sense, especially in very restricted environments or when you need Switch video centrally without relying on the networkBut for most desktop uses, development, system administration, or hybrid work across multiple operating systems, Barrier admirably covers the function of KVM, and even includes extras like a shared clipboard.

All of this means that if you work with multiple machines daily, you might seriously consider whether it's more worthwhile to spend a few minutes learning how to use Barrier than to keep manually switching keyboards, mice, or physical KVM switches. Once you have it configured and stable, the increase in comfort and efficiency in your daily work is remarkable.

Ultimately, leveraging Barrier as "KVM with Barrier" means understanding that you're replacing a physical device with a software layer that relies on your local network, with its strengths (cross-platform compatibility, no extra cables, shared clipboard, active community) and its current limitations (no drag-and-drop on Linux, pending Wayland support, some issues with Unicode and certificates). If you choose the right versions, keep the program updated, and use its support system when something goes wrong, it's a tool that can completely change the way you work with multiple computers simultaneously.