Getting core files
If CRIU crashes it's useful to build it with debug info and look into core file.
- build CRIU with debug info
- setup core file generation which depends on distro settings, usually the core generation template is sitting in /proc/sys/kernel/core_pattern, see more details at core.5
Then upload core file into debugger
gdb criu core-file and type
bt command to fetch a backtrace.
Docker keeps images in ... and logs in ...
CRIU uses ptrace, so strace can't be used in some cases. perf trace is an alternative way. It isn't so informative, but it is still better than nothing.
The crit tool can help to decode image files into a human readable format.