Build, Ship, and Run Any App, Anywhere using Docker
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The document discusses the concept of namespaces in Linux, which are essential for containerization by partitioning kernel resources. It covers various types of namespaces such as PID, network, mount, UTS, IPC, and user namespaces, explaining their functionalities and significance in managing processes and resources. Additionally, it touches on Docker's architecture and the distinction between Docker images and containers.
![5
What are they ?
root@ip-172-31-43-99:/# ls -la /proc/4015/ns/
total 0
lrwxrwxrwx 1 cgroup -> cgroup:[4026531835]
lrwxrwxrwx 1 ipc -> ipc:[4026531839]
lrwxrwxrwx 1 mnt -> mnt:[4026531840]
lrwxrwxrwx 1 net -> net:[4026531993]
lrwxrwxrwx 1 pid -> pid:[4026531836]
lrwxrwxrwx 1 user -> user:[4026531837]
lrwxrwxrwx 1 uts -> uts:[4026531838]](https://image.slidesharecdn.com/fossmeet-coep-180406111804/85/Build-Ship-and-Run-Any-App-Anywhere-using-Docker-5-320.jpg)
![UTS namespace Implementation
func main() {
cmd := exec.Command("/bin/sh")
cmd.SysProcAttr = &syscall.SysProcAttr{
Cloneflags: syscall.CLONE_NEWUTS,
}
syscall.Sethostname([]byte("inner"))
if err := cmd.Run(); err != nil {
panic(err)
}
}](https://image.slidesharecdn.com/fossmeet-coep-180406111804/85/Build-Ship-and-Run-Any-App-Anywhere-using-Docker-12-320.jpg)
Build, Ship, and Run Any App, Anywhere using Docker
- 1. Build, Ship, and Run Any App, Anywhere COEP FOSSMeet'18 Rahulkrishnan R A
- 2. About Me » Consultant @ Capgemini » Debian Contributor » Gopher » Organizer of kubernetes Meetup, Chennai Docker 101 LinkedIn linkedin.com/in/rahulkrishnanra/ Github https://github.com/rahulkrishnanfs Twitter https://twitter.com/rahulkrishnanra
- 3. 3What is namespace? » Feature of the Linux kernel that partitions kernel resources » Limits what you can see » Namespaces are the fundamental aspect of containers on Linux
- 4. 4 Types of namespace o pid (processes) o net (network stack) o mnt (mount points, filesystems) o uts (hostname) o ipc (System V IPC) o user (UIDs) o cgroups
- 5. 5 What are they ? root@ip-172-31-43-99:/# ls -la /proc/4015/ns/ total 0 lrwxrwxrwx 1 cgroup -> cgroup:[4026531835] lrwxrwxrwx 1 ipc -> ipc:[4026531839] lrwxrwxrwx 1 mnt -> mnt:[4026531840] lrwxrwxrwx 1 net -> net:[4026531993] lrwxrwxrwx 1 pid -> pid:[4026531836] lrwxrwxrwx 1 user -> user:[4026531837] lrwxrwxrwx 1 uts -> uts:[4026531838]
- 6. 6 PID namespace » Processes within a PID namespace only see processes in the same PID namespace » Each PID has its own numbering » Namespace will be killed if PID one goes away » Behavior like the “init” process » PID namespace can be nested, up to 32 nesting levels
- 7. 7 1 2 3 4, 1 5, 2 6, 3 Child PID namespace parent PID namespace
- 8. Network Namespace » Logical copy of the network stack It has its own: routes firewall rules network devices IP address » It helps to separate application/process networking » You can move network interface across netns » Newly created network namespace includes only the loopback device
- 9. Child net namespace Child net namespace Global net namespace InterfaceInterface routing NetworkInterface
- 10. Mount namespace » Processes can have their own rootfs » Mounts can be totally private or shared » In the new mount namespace, all previous mounts will be visible » Mounts/unmounts in the global namespace are visible in that namespace
- 11. UTS namespace » Appears to have different host and domain names to different processes. » UTS namespace provides a way to get information about the system with commands like uname or hostname » Simple one to implement
- 12. UTS namespace Implementation func main() { cmd := exec.Command("/bin/sh") cmd.SysProcAttr = &syscall.SysProcAttr{ Cloneflags: syscall.CLONE_NEWUTS, } syscall.Sethostname([]byte("inner")) if err := cmd.Run(); err != nil { panic(err) } }
- 13. IPC namespace » Private set of IPC objects inside namespace eg: shm
- 14. User namespace » Allows to map UID/GID » Avoid extra configuration in containers » Security improvement
- 15. Container runtime - Docker
- 16. How containers looks like? ContainersVirtual Machines
- 17. Interest on Docker – Google trends https://trends.google.co.in/trends/explore?date=today%205-y&q=docker
- 18. Docker Engine Docker Engine is a client-server application with these major components: » A REST API which specifies interfaces that programs can use to talk to the daemon and instruct it what to do » A command line interface (CLI) client ( the docker command) » A server which is a type of long-running program called a daemon process (the dockerd command)
- 20. How docker access the linux kernel?
- 21. Docker Images vs Containers Images » Lightweight, stand-alone, executable package » Includes everything needed to run a piece of software, including the code, a runtime, libraries, environment variables, and config files. Container » Runtime instance of an image—what the image becomes in memory when actually executed.
- 22. Docker Image
- 23. Sharing the docker image
- 24. “ Demo 24
- 25. “ Questions 25
- 26. “ Thanks !!! Follow me @rahulkrishnanra 26 😉