We have checkpoint/restart (CPT) and live migration in OpenVZ for ages (well, OK, since 2007 or so), allowing for containers to be freely moved between physical servers without any service interruption. It is a great feature which is valued by our users. The problem is we can't merge it upstream, ie to vanilla kernel.
Various people from our team worked on that, and they all gave up. Then, Oren Laadan was trying very hard to merge his CPT implementation -- unfortunately it didn't worked out very well either. The thing is, checkpointing is a complex thing, and the patch implementing it is very intrusive.
Recently, our kernel team leader Pavel Emelyanov got a new idea of moving most of the checkpointing complexity out of the kernel and into user space, thus minimizing the amount of the in-kernel changes needed. In about two weeks of time he wrote a working prototype. So far the reaction is mostly positive, and he's going to submit a second RFC version for review to lkml.
For more details, read the lwn.net article. After all, while I am sitting next to Pavel, Mr. Corbet ability to explain complex stuff in simple terms is way better than mine.
I tried it and was able to migrate a CentOS 7 container... but the Fedora 22 one seems to be stuck in the "started" phase. It creates a /vz/private/{ctid} dir on the destination host (with the same…
The fall semester is just around the corner... so it is impossible for me to break away for a trip to Seattle. I hope one or more of you guys can blog so I can attend vicariously.
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Do you still stand by your opinions above now in 2016?…