Hi, I'd like to use LTTng from within a non-privileged Docker container to perform user-space tracing (enable-event --userspace --tracepoint etc.). Specifically, I would like to trace a .NET Core application, which uses LTTng events to trace GC, JIT, assembly loading, and other events. My testing environment is a FC25 host with an Ubuntu 14.04 container.
I can install LTTng within the target container, but the session daemon produces the following message while loading: modprobe: ERROR: ../libkmod/libkmod.c:556 kmod_search_moddep() could not open moddep file '/lib/modules /4.12.9-200.fc25.x86_64/modules.dep.bin' Error: Unable to load module lttng-tracer DEBUG1 [1830/1830]: Failed to open /proc/lttng (in init_kernel_tracer() at main.c:2382) Error: Unable to remove module lttng-tracer Warning: No kernel tracer available Subsequent commands seem to work, but there are no traces produced. What I ran was: lttng create mysession --output /tmp lttng enable-event --userspace --tracepoint DotNETRuntime:GC* lttng start lttng stop lttng destroy Is there a way to use the LTTng session daemon in non-privileged mode, if I'm only interested in userspace tracing? I would like to avoid installing LTTng on the host system, or running privileged. In fact, the ideal workflow for me is to have a separate container image with LTTng and "attach" that container image (using docker --pid --net) to the target container that I want to analyze. But I'd settle for having LTTng in the target container if that's the only option. By the way, running LTTng from the host when the target application is in a container doesn't work either (i.e. no traces are produced). Running LTTng from the host when the target application is also on the host produces results successfully. Any suggestions would be very much appreciated. Thanks, Sasha
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