sudo /usr/bin/lttng-sessiond -vvv shows us the cause:
DEBUG1 - 08:54:51.384370 [14445/14475]: Processing client command 14 (in process_client_msg() at main.c:2989) modprobe: FATAL: Module lttng-tracer not found in directory /lib/modules/4.10.0-14-generic Error: Unable to load required module lttng-tracer DEBUG1 - 08:54:51.387309 [14445/14475]: Failed to open /proc/lttng (in init_kernel_tracer() at main.c:2721) DEBUG1 - 08:54:51.390165 [14445/14475]: Modprobe removal successful lttng-kretprobes (in modprobe_remove_lttng() at modprobe.c:126) DEBUG1 - 08:54:51.392860 [14445/14475]: Modprobe removal successful lttng-kprobes (in modprobe_remove_lttng() at modprobe.c:126) DEBUG1 - 08:54:51.396010 [14445/14475]: Modprobe removal successful lttng-ftrace (in modprobe_remove_lttng() at modprobe.c:126) DEBUG1 - 08:54:51.398841 [14445/14475]: Modprobe removal successful lttng-types (in modprobe_remove_lttng() at modprobe.c:126) Error: Unable to remove module lttng-ring-buffer-metadata-mmap-client Error: Unable to remove module lttng-ring-buffer-client-mmap-overwrite Error: Unable to remove module lttng-ring-buffer-client-mmap-discard Error: Unable to remove module lttng-ring-buffer-metadata-client Error: Unable to remove module lttng-ring-buffer-client-overwrite Error: Unable to remove module lttng-ring-buffer-client-discard Error: Unable to remove module lttng-lib-ring-buffer Error: Unable to remove module lttng-tracer Warning: No kernel tracer available DEBUG1 - 08:54:51.422146 [14445/14475]: Missing llm structure. Allocating one. (in process_client_msg() at main.c:4037) DEBUG1 - 08:54:51.422168 [14445/14475]: Sending response (size: 16, retcode: Kernel tracer not available) (in thread_manage_clients() at main.c:4456) DEBUG1 - 08:54:51.422197 [14445/14475]: Clean command context structure (in clean_command_ctx() at main.c:829) DEBUG1 - 08:54:51.422206 [14445/14475]: Accepting client command ... (in thread_manage_clients() at main.c:4310)
sudo /usr/bin/ lttng-sessiond -vvv shows us the cause:
DEBUG1 - 08:54:51.384370 [14445/14475]: Processing client command 14 (in process_ client_ msg() at main.c:2989) 4.10.0- 14-generic tracer( ) at main.c:2721) remove_ lttng() at modprobe.c:126) remove_ lttng() at modprobe.c:126) remove_ lttng() at modprobe.c:126) remove_ lttng() at modprobe.c:126) buffer- metadata- mmap-client buffer- client- mmap-overwrite buffer- client- mmap-discard buffer- metadata- client buffer- client- overwrite buffer- client- discard ring-buffer client_ msg() at main.c:4037) manage_ clients( ) at main.c:4456) manage_ clients( ) at main.c:4310)
modprobe: FATAL: Module lttng-tracer not found in directory /lib/modules/
Error: Unable to load required module lttng-tracer
DEBUG1 - 08:54:51.387309 [14445/14475]: Failed to open /proc/lttng (in init_kernel_
DEBUG1 - 08:54:51.390165 [14445/14475]: Modprobe removal successful lttng-kretprobes (in modprobe_
DEBUG1 - 08:54:51.392860 [14445/14475]: Modprobe removal successful lttng-kprobes (in modprobe_
DEBUG1 - 08:54:51.396010 [14445/14475]: Modprobe removal successful lttng-ftrace (in modprobe_
DEBUG1 - 08:54:51.398841 [14445/14475]: Modprobe removal successful lttng-types (in modprobe_
Error: Unable to remove module lttng-ring-
Error: Unable to remove module lttng-ring-
Error: Unable to remove module lttng-ring-
Error: Unable to remove module lttng-ring-
Error: Unable to remove module lttng-ring-
Error: Unable to remove module lttng-ring-
Error: Unable to remove module lttng-lib-
Error: Unable to remove module lttng-tracer
Warning: No kernel tracer available
DEBUG1 - 08:54:51.422146 [14445/14475]: Missing llm structure. Allocating one. (in process_
DEBUG1 - 08:54:51.422168 [14445/14475]: Sending response (size: 16, retcode: Kernel tracer not available) (in thread_
DEBUG1 - 08:54:51.422197 [14445/14475]: Clean command context structure (in clean_command_ctx() at main.c:829)
DEBUG1 - 08:54:51.422206 [14445/14475]: Accepting client command ... (in thread_