GDB problems inside docker
This is due to apparmor. I have a solution but it needs to be applied after each boot.
The trick is to tell apparmor to 'complain' about security violations rather than block them. This isn't the most secure workaround, I'd really like to find a better way to deal with it (like only allow ptrace and whatever else GDB requires).
To tell apparmor to complain, you need to change the line in /etc/apparmor.d/docker from:
profile docker-default flags=(attach_disconnected,mediate_deleted) {to:
profile docker-default flags=(attach_disconnected,mediate_deleted,complain) {