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