Action scripts
With the --action-script command line option, CRIU can call your action scripts (also known as hooks) at various stages of dumping/restoring. The following hooks are available:
pre-dump- called before the beginning of dump
post-dump- called when CRIU finished dumping tasks and before unfreezing them
pre-restore- called before the beginning of restore
post-restore- called when CRIU has finished restoring tasks and before unlocking the network
network-unlock- requested to unlock a container network (used by Docker and LXC)
setup-namespaces- called when the root task is alive and new set of namespaces is created to set them up
post-setup-namespaces- called after namespaces are configured
pre-resume- called at the moment when processes and resources are already restored but not yet in running state
post-resume- called at the very end, when everything is restored and processes were resumed
orphan-pts-master- called after master pty is opened and unlocked (used by Docker). Used only in RPC mode, and the notification message contains a file descriptor for the master pty.
CLI
These hooks are added with the --action-script shell-code-to-execute option. When called, the CRTOOLS_SCRIPT_ACTION environment is set to a value determining which type of action is performed.
RPC
In case of RPC, action scripts are implemented as notifications. Once CRIU service wants to execute a script, it sends an RPC message to the caller and waits for it to respond with criu_req message having notify_success = true.
Library
When using a library, one can set up a callback using the criu_set_notify routine.