Inside Docker

A small overview of virtualization technics and their schemes of work, as well as the internal structure of Docker (LXC plus AUFS)

1. Inside Docker
2. OMG! Why VirtualBox is so slow?
3. Virtualization
4. Full Virtualization Software-based Paravirtualization
5. Full x86 Virtualization Software-based Hardware assisted Paravirtualization
6. Full x86 Virtualization Operating system- level Software-based Hardware assisted Paravirtualization
7. 3 key aspects CPU virtualization Memory virtualization Device and IO virtualization
8. Privilege rings for the x86 available in protected mode Ring 0 - “Kernel” 4 rings
9. User Apps Ring 3 Ring 2 Guest OS Ring 1 VMM Ring 0 Hardware Binary translation Full virtualization using Binary translation
10. User Apps Ring 3 Ring 2 Ring 1 Paravirtualized Guest OS Ring 0 Hardware Replacing non-virtualizable OS-instructions Paravirtualization Virtualization Layer
11. User Apps Ring 3 Ring 2 Ring 1 Guest OS Ring 0 Hardware x86 VMM Root mode privilege levels Non-root mode privilege levels
12. To summarize VBox ‣ Emulates IO/Hardware devices, BIOS ‣ Use binary translation ‣ Work hard in MMU (shadowing pages table, updating TLB)
13. AUFS LXC
14. AUFS LXC Linux Containers
15. ‣ Kernel namespaces (ipc, uts, mount, pid, network and user) ‣ AppArmor and SELinux profiles ‣ Seccomp policies ‣ Chroots (using pivot_root) ‣ Kernel capabilities ‣ Control groups (cgroups)
16. Linux namespaces user utc ipc net mnt pid Process
17. Cgroups Resource limiting CPU Memory IO cpu.shares cpuset.cpus memory.limit_in_bytes blkio.throttle. {read,write}. {iops,bps}.device blkio.weight memory.stat cpuacct.stat Accounting Isolation
18. ‣ The liblxc library ‣ Several language bindings (python3, lua and Go) ‣ A set of standard tools to control the containers ‣ Container templates Parts
19. ‣ all containers uses the same kernel ‣ thus requires less resources ‣ and more lightweight ‣ takes seconds to start (fast) Pros ‣ not so isolated Cons
20. AUFS LXC
21. AUFS Layered Filesystem
22. AUFS Branch 1 Branch 2 f1 f1 f2 f2 f3 f3 f3 d1 f4 f5 d1 f4 d1 f5 f6 f6 f6 Copy on Write Write Read
23. Read AUFS Branch 1 Branch 2 f6 f6 f6 Delete f6 Whiteout f6
24. ‣ storage savings ‣ faster deployments ‣ better memory usage ‣ easier upgrades ‣ allows arbitrary changes (root filesystem is still writeable) Pros ‣ not so active development Cons
25. Resources 1. VMware “Understanding Full Virtualization, Paravirtualization, andHardware Assist” http://www.vmware.com/files/pdf/ VMware_paravirtualization.pdf 2. Namespaces in operation, part 1: namespaces overview https://lwn.net/ Articles/531114/ 3. PaaS Under the Hood http://blog.dotcloud.com/ 4. Lightweight Virtualization by Jérôme Petazzoni http:// www.socallinuxexpo.org/sites/default/files/presentations/Jerome- Scale11x%20LXC%20Talk.pdf 5. The File system http://www.tldp.org/LDP/tlk/fs/filesystem.html