Repos-que-me-gustan/devops-exercises
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Merge branch 'master' of https://github.com/bregman-arie/devops-exercises

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abregman 2020-08-29 12:37:08 +03:00
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@ -4127,6 +4127,62 @@ Docker daemon creates a new container by using the image it downloaded
Docker daemon redirects output from container to Docker CLI which redirects it to the standard output Docker daemon redirects output from container to Docker CLI which redirects it to the standard output
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<details>
<summary>What are `dockerd, docker-containerd, docker-runc, docker-containerd-ctr, docker-containerd-shim` ?</summary><br><b>
dockerd - The Docker daemon itself. The highest level component in your list and also the only 'Docker' product listed. Provides all the nice UX features of Docker.
(docker-)containerd - Also a daemon, listening on a Unix socket, exposes gRPC endpoints. Handles all the low-level container management tasks, storage, image distribution, network attachment, etc...
(docker-)containerd-ctr - A lightweight CLI to directly communicate with containerd. Think of it as how 'docker' is to 'dockerd'.
(docker-)runc - A lightweight binary for actually running containers. Deals with the low-level interfacing with Linux capabilities like cgroups, namespaces, etc...
(docker-)containerd-shim - After runC actually runs the container, it exits (allowing us to not have any long-running processes responsible for our containers). The shim is the component which sits between containerd and runc to facilitate this.
![alt text](https://i.stack.imgur.com/lAtSR.png "Docker Process")
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<summary>Describe difference between cgroups and namespaces </summary><br><b>
cgroup: Control Groups provide a mechanism for aggregating/partitioning sets of tasks, and all their future children, into hierarchical groups with specialized behaviour.
namespace: wraps a global system resource in an abstraction that makes it appear to the processes within the namespace that they have their own isolated instance of the global resource.
In short:
Cgroups = limits how much you can use;
namespaces = limits what you can see (and therefore use)
Cgroups involve resource metering and limiting:
memory
CPU
block I/O
network
Namespaces provide processes with their own view of the system
Multiple namespaces: pid,net, mnt, uts, ipc, user
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<summary>Describe in detail what happens when you run `docker pull image:tag`?</summary><br><b>
Docker CLI passes your request to Docker daemon. Dockerd Logs shows the process
docker.io/library/busybox:latest resolved to a manifestList object with 9 entries; looking for a unknown/amd64 match
found match for linux/amd64 with media type application/vnd.docker.distribution.manifest.v2+json, digest sha256:400ee2ed939df769d4681023810d2e4fb9479b8401d97003c710d0e20f7c49c6
pulling blob \"sha256:61c5ed1cbdf8e801f3b73d906c61261ad916b2532d6756e7c4fbcacb975299fb Downloaded 61c5ed1cbdf8 to tempfile /var/lib/docker/tmp/GetImageBlob909736690
Applying tar in /var/lib/docker/overlay2/507df36fe373108f19df4b22a07d10de7800f33c9613acb139827ba2645444f7/diff" storage-driver=overlay2
Applied tar sha256:514c3a3e64d4ebf15f482c9e8909d130bcd53bcc452f0225b0a04744de7b8c43 to 507df36fe373108f19df4b22a07d10de7800f33c9613acb139827ba2645444f7, size: 1223534
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<details> <details>
<summary>How do you run a container?</summary><br><b> <summary>How do you run a container?</summary><br><b>