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.
Short Answer: Mac OS is NOT Linux. That’s why you can’t run MAC Apps on Linux. Long Answer: It is based on UNIX, in that it conforms to POSIX Architecture Standards, just like Linux and BSD. POSIX stands for Portable Operating System Interface for Unix-like Operating 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.'
When Apple introduced the Macintosh on Jan. 24, 1984, it wasn't the first computer to sport a graphical user interface (GUI) on top of its operating system (OS), but it was an early success in the consumer market. At the time, most consumer computers used text-based command lines. Computer owners had to learn numerous commands to navigate file systems and run applications. The Macintosh GUI seemed like a big leap ahead -- so much so that other companies began to invest in creating their own GUI OS.
A quick glimpse at today's Mac OS X reveals that the GUI is stronger than ever. But the current Mac operating system owes a lot to other computer projects, some of which weren't under Apple's leadership. To understand how OS X works, you have to know its history.
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Shortly after the debut of the Macintosh there was a power struggle in the executive levels of leadership at Apple. Co-founder Steve Jobs found himself pushed to the edges of the company and eventually resigned. In 1988, Jobs went on to spearhead a project he called the NeXT Computer, which ran on an operating system called NEXTSTEP. Meanwhile, Apple continued to develop the Mac operating system.
Does Linux Software Work On Mac
Ultimately, NeXT received little traction in the computer market, though it was used in some high-profile applications. For example, World Wide Web founder Tim Berners Lee designed the first Web page using a NeXT computer [source: CERN]. And the executive power struggle at Apple continued as the company struggled to remain relevant. It was facing stiff competition with Microsoft's Windows OS. Apple executives considered purchasing or leasing an operating system from several different sources, including IBM. Ultimately, a phone call from Steve Jobs to Apple convinced the company to acquire NeXT in order to use its OS in Mac computers. This meant Steve Jobs was once again part of Apple.
Apple began to incorporate NeXT technology with the Mac OS. Apple also began to integrate features from a failed internal OS project codenamed Copland. In September 1997, Jobs became the interim CEO of Apple. A year later, he announced that Mac OS X -- the 10th generation of the Macintosh operating system -- would debut in 1999. On March 16 of that year, Jobs revealed the first build of Mac OS X to a group of developers. While the technical name for the operating system is Mac OS X 10.0, the company gave it the codename Cheetah. Since that first release, all OS X versions have a big-cat nickname. The most recent version as of the writing of this article is Mac OS X 10.7, also known as Lion.
Now that we've got some basic history out of the way, let's take a quick look at what operating systems actually do.