2006: Started with linux-vserver (link)? Had problems with the userspace tools, bugs, and wasn't too enthused with the attitude of some of the devs.

2008: Had another problem that cried out for lightweight virtualization. This time I tried OpenVZ which solved most of my Linux-VServer problems but brought some of its own.

Chronically out of date. Can't run it on my laptop or workstation because trying to wedge a 2.6.18 kernel into Jaunty is always a bad idea (at the time their 2.6.24 was still unstable). Even in a server environment, it's painful: I wanted to run it on linode so I had to do my own merge (on github). My kernel works for a few days, then something in the host kernel goes into an infinite loop and everything freezes until I reboot the box. Doesn't seem network, disk, or memory-related.

Luckily, by the time I was getting around to tracking it down, OpenVZ released a Xen-enabled kernel. So I installed that one. Guess what? Same thing!!

And it requires grub-pxe if the host is running under Xen. It turns out that grub-pxe doesn't work with more than 1024 MB of memory. It's not fun trying to diagnose that remotely -- the only clue is your VM won't boot (thanks to caker from Linode for help with that one, it would have taken me far longer to figure it out on my own).

So, the only way I've found to keep OpenVZ stable is to run seriously vanilla on ancient Centos or new Proxmox on bare metal. Don't run it on workstations or laptops with active users (the kernel is far too old), and don't run it under KVM or Xen.

Not limitations that I'm willing to accept.

All of those are solved by LXC. And that brings us to 2009.

Note that LXC not without its downsides. OpenVZ is much more mature and will have more features for quite a while. Here's a summary: http://www.spinics.net/lists/linux-containers/msg21439.html

Also, live Migration doesn't work yet but it's close. I really like that it uses plain old checkpoint/restart features. http://www.mail-archive.com/lxc-users@lists.sourceforge.net/msg00283.html

Contact: #lxcontainer on irc.freenode.org

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