[Nix-dev] Generating nixos-compatible binaries? And bootstrapped packages.

[Bjørn Forsman]

On 25 August 2016 at 18:54, Nick Sabalausky
<bus_nixos_list at semitwist.com> wrote:
> On 08/24/2016 01:29 PM, stewart mackenzie wrote:
>> Have a look at patchelf
>
> Ok, so according to <https://nixos.org/patchelf.html>, what I do is:
>
> % patchelf --set-interpreter PATH_TO_LOADER program_binary
> % patchelf --set-rpath LINKER_SEARCH_PATHS program_binary
>
> But how do I know what my paths for PATH_TO_LOADER and LINKER_SEARCH_PATHS
> are?

A place to start would be to look at the output of

  readelf -a $MYPROG | grep "NEEDED\|interpreter

For instance,

  $ readelf -a $(which ls) | grep "NEEDED\|interpreter"
      [Requesting program interpreter:
/nix/store/dad9vxniabwzidvvxfsfj6vb0xncsbbb-glibc-2.23/lib/ld-linux-x86-64.so.2]
   0x0000000000000001 (NEEDED)             Shared library: [libacl.so.1]
   0x0000000000000001 (NEEDED)             Shared library: [librt.so.1]
   0x0000000000000001 (NEEDED)             Shared library: [libpthread.so.0]
   0x0000000000000001 (NEEDED)             Shared library: [libc.so.6]

Then try with:

  PATH_TO_LOADER=$(nix-build -A glibc '<nixpkgs>'
--no-out-link)/lib/ld-linux-x86-64.so.2

(Assuming 64-bit program.)

When the interpreter is in place, I think you can use 'ldd' to figure
out the recursive set of libraries it needs. If not, one can do the
trial and error method by trying to run the program and seeing what it
says is missing.

LINKER_SEARCH_PATHS can be built like this:

  $ for p in acl glibc; do echo $(nix-build -A $p '<nixpkgs>'
--no-out-link)/lib; done | tr '\n' ':'
  /nix/store/mq5a5h2p9wwwbpv0i7lmjzw2a503ph22-acl-2.2.52/lib:/nix/store/gwl3ppqj4i730nhd4f50ncl5jc4n97ks-glibc-2.23/lib:

  (TODO: strip the trailing colon)

Best regards,
Bjørn Forsman