How Docker didn't invent containers (Docker Meetup Brno #1)
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This document discusses the history of container technologies beginning with FreeBSD Jails in 1998 and the origins of OpenVZ in 2001. It describes how various container features like namespaces and cgroups were developed over time by different projects and eventually merged into the Linux kernel. It notes that Docker popularized containers for application deployment but is only one of several tools for managing containers, and that OpenVZ remains the most full-featured and mature container platform overall. The document concludes that containers and Docker are not the same, and one should consider whether their actual needs are for containers generally or Docker specifically.
How Docker didn't invent containers (Docker Meetup Brno #1)
- 1. How Docker didn't invent containers Docker Meetup Brno #1 Pavel Šnajdr vpsFree.cz
- 2. Contents Containers vs. Hypervisors History of CT tech OpenVZ Containers in vanilla kernel Managing containers How Docker fits in the picture Conclusions
- 3. whoami ● vpsFree.cz ● Container based VPS community/provider ● Founder, admin, base OS dev/QA ● Now full-time ● Formerly Relbit CTO ● Working with containers in prod since 2009
- 4. Hypervisors HW Hypervisor Kernel Kernel Kernel Kernel Init Libraries Apps Init Libraries Apps Init Libraries Apps Init Libraries Apps
- 8. 1998: FreeBSD Jails ● FreeBSD 4.0 ● Resource management very limited ● Origins: a small webhosting company
- 9. 2001: SWSoft Virtuozzo 2.0 ● Started in 1999 ● Groups of processes with namespace isolation ● FS to share code and save RAM ● Resources management ● SWSoft -> Parallels ● Also in 2001 linux-vserver ● Mostly one-man show
- 10. 2004 ● Solaris Containers released (“Zones”) ● Virtuozzo for Windows ● Live kernel patching
- 11. 2005 ● OpenVZ project ● Namespaces (PID, mnt, UTS, net, IPC) ● UBC ● vzquota ● vzctl ● Goal set to upstream containers (“better late than never”)
- 12. 2006 ● OpenVZ live migration ● Rebase to RHEL4 kernel
- 13. 2007 ● IBM AIX WPARs, HP-UX SRP containers ● OpenVZ rebase to RHEL5 ● Also 2.6.20 port ● cgroups upstreamed (Google & IBM)
- 14. 2008 ● OpenVZ namespaces upstreaming ● PID, net, IPC, UTS, mnt ● LXC
- 15. 2010 ● OpenVZ ● Rebase to RHEL6 kernel ● VSwap (simplified UBC) ● ploop (CT-in-a-file) ● on-demand allocation ● instant snapshots ● online resize, compact, merge ● write tracker
- 16. 2011 ● CRIU proposed ● Checkpoint: get stuff from /proc debug fac. ● Restore: read dump & recreate environment ● LinuxCon 2011 Prague ● “There can be only one” ... container tech in vanilla ● Avoid Xen vs. KVM mess
- 17. 2012 ● CRIU 0.1 released ● vzctl 4.0 with support for upstream kernel
- 18. 2013 ● Docker ● lmctfy ● CoreOS ● vzctl adds IO limits ● user namespace in vanilla
- 19. 2014 ● vzctl 4.8, faster live migration ● Parallels announce PCS and OpenVZ to merge into common open-source code-base
- 20. 2015 ● OpenVZ RHEL7 kernel beta ● CRIU for migration ● cgroups replacing UBC ● vzctl not compatible yet ● public Git repo http://src.openvz.org/
- 21. OpenVZ and Docker ● Docker inside https://openvz.org/Docker_inside_CT ● Docker outside https://github.com/docker/libcontainer/pull/434 ● Docker and CRIU ● work in progress
- 22. Containers in vanilla kernel ● Any of (cgroups + namespaces) = container ● Cgroups (blkio, cpu, cpuacct, cpuset, devices, freezer, ns) ● Namespaces (user, net, PID, UTS, mnt, IPC)
- 23. Container management tools ● LXC ● LXD ● Docker ● libvirt-lxc ● systemd-nspawn ● vzctl ● lmctfy ● libct https://github.com/xemul/libct ● “Libvirt for containers”
- 25. Conclusions ● Containers != Docker ● Docker = single (very) limited way of using container tech for apps deployment ● Reinvent the wheel approach... (PID #1, logs...) ● Most mature container tech = OpenVZ ● Best isolation (eg. Kmem) ● Most features ● Do you actually want Docker or containers?
- 26. Q/A ● Questions? Anytime -> snajpa@snajpa.net