LTTng core dump snapshot handler Christian Babeux, June 2013 This is a custom core dump program that will be called when a core dump occurs. The program will save the core data in CORE_PATH and also, if a root session daemon is running, will record a snapshot of tracing data using the lttng command line utility. The core dump snapshot handler can be installed by using the provided install.sh script or by adding the appropriate program pipe line to /proc/sys/kernel/core_pattern. Refer to core(5) for more information about the Linux kernel core dump handling and custom handler mechanism. Installation: # ./install.sh Backup current core_pattern in core_pattern.bkp. Successfully installed core_pattern. How to use: You can use the provided test.sh script to test that the core dump snapshot handler is working properly: # ./test.sh Setup coredump-handler... Session coredump-handler created. Default snapshot output set to: /tmp/lttng/snapshot Snapshot mode set. Every channel enabled for that session will be set in overwrite mode and mmap output kernel event sched_switch created in channel channel0 Tracing started for session coredump-handler Sleeping... Crashing... Segmentation fault (core dumped) Sleeping... Waiting for data availability Tracing stopped for session coredump-handler Session coredump-handler destroyed Core dump will be available in /tmp/lttng/core. Snapshot will be available in /tmp/lttng/snapshot. # tree /tmp/lttng /tmp/lttng ├── core │   └── core.29085 └── snapshot └── snapshot-1-20130719-175041-0 └── kernel ├── channel0_0 ├── channel0_1 ├── channel0_2 ├── channel0_3 └── metadata Chaining with other core dump handler: Some Linux distributions already use their own core dump handler (such as systemd 'systemd-coredump' utility). It is possible to chain these core dump utility with the core dump snapshot handler. In order to achieve this, the core dump snapshot handler must be first in the chain (e.g. installed in /proc/sys/kernel/core_pattern) and the other core dump handler must be called from within the core dump snapshot handler script. Example (chaining with systemd systemd-coredump): # cat /proc/sys/kernel/core_pattern |/path/to/lttng/handler.sh %p %u %g %s %t %h %e %E %c In LTTng handler.sh script: [...] # Save core dump from stdin. #$MKDIR_BIN -p "${CORE_PATH}" #$CAT_BIN - > "${CORE_PATH}/${CORE_PREFIX}.$p" # Optional, chain core dump handler with original systemd script. $CAT_BIN - | /usr/lib/systemd/systemd-coredump $p $u $g $s $t $e [...]