service with shared libraries

[Andrei Porumb]

Hello all,

                I need to use Ubuntu Snappy to develop a service. The service has "special communication needs"... err... AMQP... so it needs a shared library to do so.

                The code is written in C. For the executable to load the shared library, it needs to have set LD_LIBRARY_PATH. So the service is started by a bash script that doesn't do much, except:

                #!/bin/sh
export LD_LIBRARY_PATH=./bin
./bin/FunkyTv
echo this line should never be executed.

This is the content of package.yaml

name: simplesampleamqp
version: 45
icon: meta/icon.png
maintainer: anporumb at microsoft.com
services:
- name: sum
   description: SomeService
   start: bin/sum.sh
   caps: networking

Problem: the service doesn't start.

Observations: if the app is run from the command line (as a regular app), the app runs just fine and performs as expected.
When run as a service, there's no life.

Journalctl helps a little here, and this is the output:


ubuntu at localhost:/apps/simplesampleamqp/current$ sudo journalctl -f -u simplesampleamqp_sum_45
-- Logs begin at Sun 2015-04-12 16:33:29 UTC. --
Apr 13 16:59:12 localhost.localdomain systemd[1]: Started SomeService.
Apr 13 16:59:12 localhost.localdomain systemd[1]: Starting SomeService...
Apr 13 16:59:12 localhost.localdomain sum.sh[2920]: Segmentation fault
Apr 13 16:59:12 localhost.localdomain sum.sh[2920]: this line should never be executed.

The segmentation fault happens (as far as I can tell) before the first line in main. Since this is C code (as opposed to C++) there cannot be other code executed before main.

Further investigation revealed that in the small script that attempts to start the service there cannot be just any command. For example, "ldd" cannot be there (if it is, there's going to be a DENIAL something like : Apr 12 19:53:10 localhost.localdomain kernel: audit: type=1400 audit(1428868390.904:62): apparmor="DENIED" operation="exec" profile="simplesampleamqp_sum_44" name="/usr/bin/ldd" pid=2310 comm="sum.sh" requested_mask="x" denied_mask="x" fsuid=0 ouid=0). Echo is fine to be in the script...

I guess it all boils down to: how does one write some service in C that needs some shared libraries and loads them and executes? As an "app" the executable runs fine...


Any hints/help is greatly appreciated.

Best Regards,
Andrei Porumb



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