[Nix-dev] Question about dockerTools layering

[Tobias Pflug]

> On 23 Sep 2016, at 22:01, Luca Bruno <lethalman88 at gmail.com> wrote:
> 
> Yes, you can create an image with only node_modules and then layer on top of it another image with fromImage.
> 
> You can make the node_modules symlink in the base image. Then only update assets in the upper image.
> 

I guess this is the part where I am somewhat confused - when those are separated how do I create the symlink. Should i be creating a symlink to some absolute path in the node_modules image and then symlink to that absolute path in the other one?

I feel silly for asking but i do have some mental block on that ;)

>> On Fri, Sep 23, 2016 at 8:38 PM, Tobias Pflug <Tobias.Pflug at gmx.net> wrote:
>> Hi,
>>  
>> I recently started using dockerTools.buildImage for a nodejs based project. It's working
>> fine but I am hitting a mental block trying to introduce layers - I don't want to always push
>> around node_modules.
>>  
>> My current setup is something like the following:
>>  
>> # default.nix
>> dockerImage = with pkgs; dockerTools.buildImage {
>>   name = "foo";
>>   contents = [ nodejsApp ];
>>   config = {
>>     Cmd = [ "${nodejs-6_x}/bin/node" "${nodejsApp}/index.js" ];
>>     WorkingDir = "${nodejsApp}"
>>   };
>> };
>>  
>> # nodejsApp.nix
>> stdenv.mkDerivation {
>>   name = "nodejsApp";
>>   src = ...
>>   buildInputs = [ assets nodeModules ];
>>   installPhase = ''
>>     mkdir -p $out
>>     ln -s ${nodeModules}/node_modules $out/node_modules
>>     ln -s ${assets} $out/assets
>>     ...
>>   '';
>> }
>>  
>> So basically I have a derivation for my app and I symlink in the node_modules. Now if I want to avoid pushing
>> the node_modules to my docker registry if they are unchanged I would have to create a docker image that contains
>> only the node_modules and specify that docker image as `fromImage` argument in my buildImage call I assume?
>>  
>> I'm just not quite sure to make it all fit together. Maybe someone could help me out a bit?
>> Thanks in advance!
>>  
>> best regards,
>> Tobi
>> 
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> 
> 
> 
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> NixOS Linux
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