SNAP how to use dynamic linker ldconfig or LD_LIBRARY_PATH

[schwebo]

Good Morning,

i have a applikation /binary which i want to pack to a SNAP. I setup a Linux VM on my PC (amd64).

to execute my app directly i have to setup the dynamic-runtime linker in order to copy my own config file with lib pathes to

cp myConfigFileWithPathes.conf /etc/ld.so.conf.d/
ldconfig

after thas.  i can create a SNAP on my VM target ,  and i can this snap...

So my question:

But how can i do this for a SNAP on a xCtrl Hardware? How can i setup my snapcraft, that the dynamic linker pathes will autmatice setup according to the target!?  I read about the $LD_CONFIG_PATH

I tried so something like that in my app in the snap yaml (but it does not work)

environment:

LD_LIBRARY_PATH: $LD_LIBRARY_PATH:my_pathes_from_the_config_file

But wenn i build the snap i still get the followed warnings: (but this libs normal resolve from the dynamic link in the conf file)

This part is missing libraries that cannot be satisfied with any available stage-packages known to snapcraft:
- home/xctrlvm/AppEngine/drivers/halcon/libhalcon.so.20.11.1
- home/xctrlvm/AppEngine/drivers/halcon/libhalconc.so.20.11.1
- home/xctrlvm/AppEngine/drivers/halcon/libhalconcpp.so.20.11.1
- home/xctrlvm/AppEngine/drivers/halcon/libhdevenginecpp.so.20.11.1
- home/xctrlvm/AppEngine/libeuler_log_frontend.so.1
- home/xctrlvm/AppEngine/libeuler_plugin_loader.so.1

[nickH]

Hello, 

some topics from my side:

• Did you setup your Development Environment with one of the two options we recommend in the SDK Docu on GitHub?
• Please have a look into the SDK and see how the sample snaps for ctrlX CORE in the different programming languages get build.
• For detailed information on how to build a snap see: snapcraft - creating a snap  

I'm sorry, but I didn't understand everything from your post. Can you please explain your issue and your desired snap build process a little bit deeper (maybe also share your snapcraft.yaml)? 

Best regards,

Nick

[schwebo]

Good morning nick,

thank for response. I'll try to explany it clearer.

First, i setup a VM with sdk and so on, and iam able to build the sample-snaps form the sdk. until then everything is fine:) 

Second, i am a noob in Linux and SNAP, but i try to learn this technologies and do my best.

I have a application binary-builds for Linux arm64 and amd64. An i can run this appilcation in my linux VM whitout SNAP. To get the applikation running, i have to copy a .conf (from my app) file to the /etc/ld.so.conf.d/ folder which contians lib-path from my app. And with ldconfig i announce the dynamic linker of linux that ther are new lib locations... than i can execute my app from the cli .

Now, i want to pack my Application to a SNAP. So, my first though, create a snapcraft with a app and and  part (plugin:dump) with the source of my binary (which mention above). the problem ist now, that the SNAP build process has to the same which i have done above for the dynamic-linker. So is read soming about the LD_PATH_LIBRARY. to provide dynamic-linker path something like this:

export LD_LIBRARY_PATH="$LD_LIBRARY_PATH:$SNAP/path/to1/:$SNAP/path/to2/:$SNAP/path/to3/"

but how can i to that with SNAP implcity!?

So i understand, is the a .snap file which is build, contains ALL Libs which are needed, that meand the lib from the dynanamic.linker are alos copies to the snap file !?!?!?!

Thank you

[nickH]

Hello, 

Just to show some basics about snaps I copied out an extract from the snapcraft.yaml of the hello.world sample from the SDK and added some comments: 

# define how apps & services are exposed to host system
apps:
  HelloWorld:                            #name of your application (binary build)  
    command: HelloWorld          #this will be the command to run the service
    plugs:                                    #plugs to connect to interfaces
      - network
    daemon: simple                     #declares that your application gets started by the system deamon
    passthrough:                          #restarts the application if it shuts down after 10 sec
      restart-condition: always             
      restart-delay: 10s  

#describes how the binary application (from folder ./generated/build) gets packed (dumped) into the snap 
parts:
  helloworld:
    plugin: dump
    source: ./generated/build

 Please a look into the snpacraft.yaml reference. It describes all the details snapcraft needs to build a snap. 

---

@schwebo wrote:

So i understand, is the a .snap file which is build, contains ALL Libs which are needed, that meand the lib from the dynanamic.linker are alos copies to the snap file !?!?!?!

---

Yes, this is true. Snaps in general are self contained and therefor have to have all needed dependencies inside.

I hope I could clarify some things. You can share your snapcraft.yaml (with some comments) so we can have a look at your snap build mechanism. 

[JohannesA · Accepted solution]

Hi 

maybe you are looking for "stage-packages" ? 

If you have to add own libraries you can dump it into the snap using the dump plugin.

$SNAP/lib:$SNAP/usr/lib:$SNAP/usr/lib/x86_64-linux-gnu (on amd64 architecture) are default part of the LD_LIBRARY_PATH

If you add your library to another directory within your snap you have to extend the environment variable e.g.:

apps:
example-app:
 [...]
 environment:
    LD_LIBRARY_PATH: $LD_LIBRARY_PATH:$SNAP/<example-directory>

Regards

Johannes