For almost two years Mike Rapoport and I have been working on lazy
process migration. Lazy process migration (or post-copy migration) is a
technique to decrease the process or container downtime during the live
migration. I described the basic functionality in the following previous
articles:

Those articles are not 100% correct anymore as we changed some of the
parameters during the last two years, but the concepts stayed the same.

Mike and I started about two years ago to work on it and the latest
CRIU release
(3.5)
includes the possibility to
use lazy migration. Now that the post-copy migration feature has been
merged from the criu-dev branch to the master branch it is part of
the normal CRIU releases.

With CRIU’s 3.5 release lazy migration can be used on any kernel which
supports
userfaultfd.
I already updated the CRIU packages in Fedora to 3.5 so that lazy
process migration can be used just by installing the latest CRIU
packages with dnf (still in the testing repository right now).

More information about container live migration in our upcoming Open
Source Summit Europe talk: Container Migration Around The
World
.

My pull request to
support lazy migration in
runC was also recently
merged, so that it is now possible to migrate containers using pre-copy
migration and post-copy migration. It can also be combined.

Another interesting change about CRIU is that it started as x86_64
only and now it is also available on aarch64, ppc64le and s390x.
The support to run on s390x has just been added with the previous 3.4
release and starting with Fedora 27 the necessary kernel configuration
options are also active on s390x in addition to the other supported
architectures.