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• Open Source Software for running Windows applications on other operating systems. Such as Linux, macOS, & BSD. Instead of simulating internal Windows logic like a virtual machine or emulator, Wine translates Windows API calls into POSIX calls on-the-fly, eliminating the performance and memory penalties of other methods and allowing you to.
• Links to popular distribution download pages. Below you'll find links that lead directly to the download page of 25 popular Linux distributions.

Knoppix: UPDATE: New link Knoppix is one of the better tools for rescuing data from sick.

Linux users who want to run Windows applications without switching operating systems have been able to do so for years with Wine, software that lets apps designed for Windows run on Unix-like systems.

There has been no robust equivalent allowing Mac applications to run on Linux, perhaps no surprise given that Windows is far and away the world's most widely used desktop operating system. A developer from Prague named Luboš Doležel is trying to change that with 'Darling,' an emulation layer for OS X.

'The aim is to achieve binary compatible support for Darwin/OS X applications on Linux, plus provide useful tools that will aid especially in application installation,' Doležel's project page states. Darwin is Apple's open source operating system, which provides some of the backend technology in OS X and iOS. The name 'Darling' combines Darwin and Linux. Darling works by 'pars[ing] executable files for the Darwin kernel... load[ing] them into the memory... and execut[ing] them.'

But there is a ways to go. 'Darling needs to provide an ABI-compatible [application binary interface] set of libraries and frameworks as available on OS X... by either directly mapping functions to those available on Linux, wrapping native functions to bridge the ABI incompatibility, or providing a re-implementation on top of other native APIs,' the project page notes.

Doležel, who started Darling a year ago, described the project and its progress in an e-mail interview with Ars. Darling is in the early stages, able to run numerous console applications but not much else. 'These are indeed the easiest ones to get working, albeit 'easy' is not the right word to describe the amount of work required to achieve that,' Doležel said. 'Such applications include: Midnight Commander, Bash, VIM, or Apple's GCC [GNU Compiler Collection]. I know it doesn't sound all that great, but it proves that Darling provides a solid base for further work.'

Users must compile Darling from the source code and then 'use the 'dyld' command to run an OS X executable,' Doležel said. One roadblock is actually getting Mac .dmg and .pkg application files working on a Linux system. Because doing so isn't that straightforward, Doležel said, 'I've written a FUSE module that enables users to mount .dmg files under Linux directly and without root privileges. An installer for .pkg files is underway.'

Unix/Linux synergy

The fact that OS X is a Unix operating system provides advantages in the development process. 'This saved me a lot of work,' Doležel explained. 'Instead of implementing all the 'system' APIs, it was sufficient to create simple wrappers around the ones available on Linux. I had to check every function for ABI compatibility and then test whether my wrapper works, so it wasn't as easy as it may sound.'

Another lucky break not available to Wine developers is that Apple releases some of the low-level components of OS X as open source code, 'which helped a lot with the dynamic loader and Objective-C runtime support code,' Doležel noted.

But of course, the project is an extremely difficult one. Doležel isn't the first to try it, as Darling was initially based on a separate project called 'maloader.' Doležel said he heard from another group of people 'who started a similar project before but abandoned the idea due to lack of time.'

Doležel was actually a novice to OS X development when he started Darling, being more familiar with OS X from a user's perspective than a developer's perspective. 'I have personally looked for something like Darling before, before I realized I would have to start working on it myself,' he said.

Darling relies heavily on GNUstep, an open source implementation of Apple's Cocoa API. GNUstep provides several core frameworks to Darling, and 'the answer to 'can it run this GUI app?' heavily depends on GNUstep,' Doležel said. Doležel is the only developer of Darling, using up all his spare time on the project.

No reverse-engineering

Doležel isn't reverse-engineering Apple code, noting that it could be problematic in terms of licensing and also that 'disassembling Apple's frameworks wouldn't be helpful at all because Darling and the environment it's running in is layered differently than OS X.'

The development process is a painstaking one, done one application at a time. Doležel explains:

To improve Darling, I first take or write an application I'd like to have running. If it is someone else's application, I first examine it with one of the tools that come with Darling to see what frameworks and APIs it requires. I look up the APIs that are missing in Apple's documentation; then I create stub functions for them and possibly for the rest of the framework, too. (Stub functions only print a warning when they are called but don't do any real work.)

The next step is to implement all the APIs according to the documentation and then see how the application reacts. I also add trace statements into important functions to have an insight into what's happening. I believe this is very much like what Wine developers do.

When things go wrong, I have to use GDB [GNU Debugger] to debug the original application.

It is rather unfortunate that Apple's documentation is often so poorly written; sometimes I have to experiment to figure out what the function really does. Many OS X applications seem to contain complete pieces of example code from Apple's documentation, presumably because one would have to spend a lot of time getting to understand how the APIs interact. This is why I appreciate open source so much—when the documentation is sketchy, you can always look into the code.

Years of development are needed. Similar to Wine, 'Having a list of applications known to be working is probably the best way to go,' Doležel said.

Darling should work on all Linux distributions, he said, with the catch that 'many apps for OS X are 32-bit only, and installing 32-bit packages on a 64-bit Linux system could be tricky depending on your distribution. I personally use Gentoo Linux, so I'm gradually creating a Portage overlay that would compile Darling and all dependencies for both 32-bit and 64-bit applications.'

Doležel would like to bring Angry Birds, other games, and multimedia applications to Linux. Darling could potentially 'be used to run applications compiled for iOS,' he writes on the project site. This will also be a challenge. 'The intention is to support the ARM platform on the lowest levels (the dynamic loader and the Objective-C runtime),' he writes. 'Rewriting the frameworks used on iOS is a whole different story, though.'

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If you've upgraded to macOS Mojave or later, follow these steps to keep it up to date:

1. Choose System Preferences from the Apple menu , then click Software Update to check for updates.
   
2. If any updates are available, click the Update Now button to install them. Or click ”More info” to see details about each update and select specific updates to install.
   
3. When Software Update says that your Mac is up to date, the installed version of macOS and all of its apps are also up to date. That includes Safari, iTunes, Books, Messages, Mail, Calendar, Photos, and FaceTime.

To find updates for iMovie, Garageband, Pages, Numbers, Keynote, and other apps that were downloaded separately from the App Store, open the App Store on your Mac, then click the Updates tab.

To automatically install macOS updates in the future, including apps that were downloaded separately from the App Store, select ”Automatically keep my Mac up to date.” Your Mac will notify you when updates require it to restart, so you can always choose to install those later.

How to get updates for earlier macOS versions

If you're using an earlier macOS, such as macOS High Sierra, Sierra, El Capitan, or earlier,* follow these steps to keep it up to date:

1. Open the App Store app on your Mac.
2. Click Updates in the App Store toolbar.
3. Use the Update buttons to download and install any updates listed.
4. When the App Store shows no more updates, the installed version of macOS and all of its apps are up to date. That includes Safari, iTunes, iBooks, Messages, Mail, Calendar, Photos, and FaceTime. Later versions may be available by upgrading your macOS.

To automatically download updates in the future, choose Apple menu  > System Preferences, click App Store, then select ”Download newly available updates in the background.” Your Mac will notify you when updates are ready to install.

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* If you're using OS X Lion or Snow Leopard, get OS X updates by choosing Apple menu  > Software Update.

How to get updates for iOS

Learn how to update your iPhone, iPad, or iPod touch to the latest version of iOS.

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Mac Software Linux

• Learn how to upgrade to the latest version of macOS.
• Find out which macOS your Mac is using.
• You can redownload apps that you previously downloaded from the App Store.
• Your Mac doesn't automatically download large updates when it's using a Personal Hotspot.