[Libguestfs] guestfs_launch() fails when C application is started as a systemd service

[Peter Dimitrov]

Here are strace outputs per process.

strace_output.22076 is the plugin's pid. (A little before forking)
strace_output.22077  runs qemu-img
strace_output.22078 is a mystery to me
strace_output.22079 is rm -rf to the overlay image and its temporary dir.

Best Regards,
Peter


On Wed, Nov 7, 2018 at 4:38 PM Richard W.M. Jones <rjones at redhat.com> wrote:

> On Wed, Nov 07, 2018 at 01:37:03PM +0200, Peter Dimitrov wrote:
> > > That makes no sense because we are supposed to have just forked
> > successfully
> >
> > I just realized libguestfs uses fork. Now we know why qemu-img worked - I
> > launched it with popen.
> >
> > > So it must be something to do with collectd and how it runs programs.
> > > Is it using LD_PRELOAD trickery, or replacing libc, or using seccomp?
> >
> > If I understand the question correctly - it's about how collectd loads
> its
> > plugins? If so it uses:
> >
> > static int plugin_load_file(const char *file, _Bool global) {
> >   void (*reg_handle)(void);
> >   int flags = RTLD_NOW;
> >     if (global)
> >       flags |= RTLD_GLOBAL;
> >   void *dlh = *dlopen*(file, flags);
> >   //...
> >   reg_handle = (void (*)(void))*dlsym*(dlh, "module_register");
> >   //...
> >   *(*reg_handle)();*
> > }
> >
> >
> > Does this give any clues?
>
> Can you strace the collectd process around the point where qemu-img is
> run?  It may gives some clues.
>
> Rich.
>
> --
> Richard Jones, Virtualization Group, Red Hat
> http://people.redhat.com/~rjones
> Read my programming and virtualization blog: http://rwmj.wordpress.com
> libguestfs lets you edit virtual machines.  Supports shell scripting,
> bindings from many languages.  http://libguestfs.org
>
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