nix-alien

Introduction

You are running nix/NixOS and have ever encountered the following problem?

$ ./bb
bash: ./bb: No such file or directory

Fear not, now there is nix-alien which will download necessary dependencies for you.

$ ./nix-alien bb            --> Run the binary inside a FHS shell with all needed shared dependencies to execute the binary
$ ./nix-alien-ld bb         --> Spawns you inside a shell with NIX_LD_LIBRARY_PATH set to the needed dependencies, to be used with nix-ld
$ ./nix-alien-find-libs bb  --> Lists all libs needed for the binary

Usage (Flakes)

Assuming you have nix already installed:

$ nix-shell -p nixUnstable nix-index
$ nix-index # this will take a long time
$ nix run --experimental-features 'nix-command flakes' "github:thiagokokada/nix-alien" -- ~/myapp

This will run nix-alien on ~/myapp binary with a FHSUserEnv including all shared library dependencies. The resulting default.nix file will be saved to $XDG_CACHE_HOME/nix-alien/ /default.nix , making the next evaluation faster. You can also pass --recreate flag to force the recreation of default.nix file

You can edit your /etc/nix/nix.conf or ~/.config/nix/nix.conf file and add the following line to avoid having to pass --experimental-features flag every time:

experimental-features = nix-command flakes

From here on this guide will assume the above configuration is done for brevity.

In case you're using nix-ld, there is also nix-alien-ld:

$ nix run "github:thiagokokada/nix-alien#nix-alien-ld" -- ~/myapp 

This will spawn a mkShell instead with NIX_LD_LIBRARY_PATH and NIX_LD setup. The resulting shell.nix file will be saved to $XDG_CACHE_HOME/nix-alien/ /shell.nix , making the next evaluation faster. You can also pass --recreate flag to force the recreation of shell.nix file

If you want to use the fzf based menu to find the libraries for scripting purposes, you can run:

$ nix run "github:thiagokokada/nix-alien#nix-alien-find-libs" -- ~/myapp 

This will print the found libraries on the stdout. The informational messages are printed to stderr, so you can easily redirect them to /dev/null if needed.

To avoid the slow startup of nix-index, you can also download a pre-computed index from nix-index-database:

$ nix run "github:thiagokokada/nix-alien#nix-index-update"

Usage (non-Flakes)

$ $(nix-build default.nix --no-out-link)/bin/nix-alien
$ $(nix-build default.nix --no-out-link)/bin/nix-alien-ld
$ $(nix-build default.nix --no-out-link)/bin/nix-alien-find-libs
$ $(nix-build nix-index-update.nix --no-out-link)/bin/nix-index-update

Limitations

Binaries loading shared libraries dynamically (e.g.: with dlopen) will probably not work with this script. However, this script can still be useful to create an initial default.nix or shell.nix, that can be populated later with the runtime dependencies of the program.

Technical Description

This Python program allows you to download ELF binaries and use them right away! This is achieved by enumerating the shared library dependencies from the ELF header and then searching for the equivalent library in nixpkgs. This is done by querying nix-locate locally.

To be able to use nix-locate, first, the index has to be build. This is done by running nix-index and waiting 10-15 minutes. To speed-up this process, this repo also includes nix-index-update script, that downloads the index from nix-index-database.

Credits

• Inspired by Lassulus/nix-autobahn
• Thanks to Mic92/nix-ld and bennofs/nix-index, since without them this project wouldn't be possible