Filesystem Virtualization with Runner

Runner is a utility for launching programs under GoboLinux that ensures that the filesystem view of a process will match its dependencies. In other words, Runner eliminates the possibility of library conflicts when running an executable.

Runner is a filesystem virtualization tool that sets up a constrained view of /System/Index for a process based on the executable program’s Dependencies file. It is run as a wrapper, e.g. Runner SomeApp.

Runner builds a custom mount table for the process, like container tools do, but without duplicating files. It dynamically picks the correct parts of your /Programs tree. This approach is feasible in GoboLinux due to way programs are each confined to their own subdirectories.

Preparing the filesystem view

All you have to do is to make sure the dependencies of the program you want to run are correctly listed under the program’s Resources directory - more specifically, in the Dependencies file at /Programs/Name/Version/Resources/Dependencies. You may list program names (e.g., LibPNG), specify a particular version (as in LibPNG 1.4.4) or even let Runner pick the best version given a certain range (e.g., LibPNG >= 1.4.0, < 1.5.0).

Most likely, the program you want to run will already have a sane Dependencies file - every binary package we distribute will have one, just like every compilation recipe do.

The Compile tool

Compile makes use of Runner to control the environment for building software packages. When you type Compile Foo, Compile fetches the recipe for Foo and passes both the Dependencies and BuildDependencies files of that recipe to Runner. This ensure that the right versions of the libraries, headers, and executables needed by that package will be mapped onto /System/Index.

Spawning an application with Runner

For regular GoboLinux packages, simply type Runner application_name. Runner will figure from which entry under /Programs application_name comes from, and will create a custom filesystem view for that application by overlaying its dependencies over /System/Index.

For non-regular GoboLinux packages, such as third-party executables downloaded on your home directory, you can hand-craft a Dependencies file and then provide that file to Runner, as in Runner -d MyDependenciesFile ./third_party_app.

Multi-arch setups

Running a 32-bit application on a 64-bit distro is no different with Runner. Provided that you have the 32-bit dependencies installed under /Programs (such as Glibc/2.18-i686 and Bash/3.1-i686), the Dependencies file of your program simply needs to state the versions of the 32-bit packages it relies on. Afterwards, simply type Runner <application_name> and you are all set.