On Mon, 20.04.15 14:59, Adrian Reber ([email protected]) wrote: > Using CRIU I have been migrating processes from one system to another > for the last few months (even years). I am now interested in migrating > processes under systemd's control. Before starting to look how to make > it work I wanted to know if there has been any discussion if and how > systemd and CRIU can work together?
Not that I was aware of. Personally I do not really believe in the idea of CRIU. I mean, I can see that people want the functionality, but given the amount of context processes maintain about the system I find it quite illusionary that this can work for any but the most simple programs. > Dumping a process under systemd's control should be no problem. > After criu has dumped the process (and killed it) systemd should know > that it does not need to restart the process, but even if the process is > restarted by systemd it does not hurt the process migration. > > The interesting part happens on the system where the process wants to be > migrated to. After the process has been dumped and transfered from the > source system to the destination system it needs to be restarted. So far > this works with different tested processes (postgresql is my current > test process). If I want to restore the process as a systemd child > process I have the problem that the process would have to be re-parented > to systemd after restarting which is not possible in Linux. Therefore I > need the help of systemd. > > My plan now would be to transfer the process to the destination > system and tell systemd I want to restore a process which should be > under systemd's control after the restore has completed. Therefore > systemd needs to run criu with the option to restore the new process as > a criu sibling. Thus systemd would be the correct parent process. > > Is this something which would be useful to integrate into systemd? > I have some ideas how this could be implemented and how the user > interfaces could look like. Before going in too much detail I want to > find out if this is a direction which makes sense. systemd has no provisions for anything like this and I have doubts it really should have. I mean, normal programs retain ccess to the cgroup tree, so you could readd whatever you restore back in the cgroups, but that's hardly sufficient to make systemd aware of a process like this properly. Lennart -- Lennart Poettering, Red Hat _______________________________________________ systemd-devel mailing list [email protected] http://lists.freedesktop.org/mailman/listinfo/systemd-devel
