docker stuff

categories/devops/docker.md

@@ -1,45 +1,98 @@
-# Orchestration
-
-## Rancher
+# Docker
 
 Easy to use, just drag and drop things.
 
 ## Benefits of using Docker
 
-	- escape the app dependency matrix
-	- Solve the environment issue. it works on my machine.
+- Escape the app dependency matrix
+- Solve the environment issue. it works on my machine.
+- Very low resource allocation cost when compare with Virtual Machine. So on the same machine, you can run more containers and spend much less time.
+
+## How Docker works
+
+Very useful blog talking about how docker works internally: [Understanding the Docker Internals](https://medium.com/@nagarwal/understanding-the-docker-internals-7ccb052ce9fe)
+
+![Docker](https://raw.githubusercontent.com/wahyd4/knowledge-mind-mapping/master/assets/images/docker.png)
+
+Docker use
+
+* Namespaces
+* Cgroups
+* Network
+* Union File Systems
+
+to isolate all kinds of resources.
+
+### Namespaces
+
+Docker makes use of kernel namespaces to provide the isolated workspace called the container. When you run a container, Docker creates a set of namespaces for that container. These namespaces provide a layer of isolation. Each aspect of a container runs in a separate namespace and its access is limited to that namespace.
+Docker Engine uses the following namespaces on Linux:
+
+- `PID` namespace for process isolation.
+- `NET` namespace for managing network interfaces.
+- `IPC` namespace for managing access to IPC resources.
+- `MNT` namespace for managing filesystem mount points.
+- `UTS` namespace for isolating kernel and version identifiers.
+
+### Cgroups
+
+Docker also makes use of kernel control groups for resource allocation and isolation. A cgroup limits an application to a specific set of resources. Control groups allow Docker Engine to share available hardware resources to containers and optionally enforce limits and constraints.
+Docker Engine uses the following cgroups:
+
+- Memory cgroup for managing accounting, limits and notifications.
+- HugeTBL cgroup for accounting usage of huge pages by process group.
+- CPU group for managing user / system CPU time and usage.
+- CPUSet cgroup for binding a group to specific CPU. Useful for real time applications and NUMA systems with localized memory per CPU.
+- BlkIO cgroup for measuring & limiting amount of blckIO by group.
+- net_cls and net_prio cgroup for tagging the traffic control.
+- Devices cgroup for reading / writing access devices.
+- Freezer cgroup for freezing a group. Useful for cluster batch scheduling, process migration and debugging without affecting prtrace.
+
+### Union File Systems
+
+Union file systems operate by creating layers, making them very lightweight and fast. Docker Engine uses UnionFS to provide the building blocks for containers. Docker Engine can use multiple UnionFS variants, including AUFS, btrfs, vfs, and devicemapper.
+
+### Docker VS VM
+
+![Docker vs VM](https://raw.githubusercontent.com/wahyd4/knowledge-mind-mapping/master/assets/images/container.png)
+
 ## Network
 
 - Bridge
 - Host
 
-## Tips
+## CMD
 
-	- difference between `cmd` and `entrypoint`
-	- difference between `copy` and `add`
+- has three forms
+- CMD ["executable","param1","param2"]
+	- exec form, preferred
+- CMD ["param1","param2"]
+	- as default parameters to ENTRYPOINT
+- CMD command param1 param2
+	- shell form
+- The main purpose of a CMD is to provide defaults for an executing container. These defaults can include an executable, or they can omit the executable, in which case you must specify an ENTRYPOINT instruction as well.
+- If CMD is used to provide default arguments for the ENTRYPOINT instruction, both the CMD and ENTRYPOINT instructions should be specified with the JSON array format.
+- docker run could override the default specified in CMD.
 
-        Basically they are similar, copy files and folder to destination. While ADD has some features (like local-only tar extraction and remote URL support) that are not immediately obvious. Consequently, the best use for ADD is local tar file auto-extraction into the image, as in ADD rootfs.tar.xz /.
-- CMD
-	- has three forms
-		- CMD ["executable","param1","param2"]
-			- exec form, preferred
-		- CMD ["param1","param2"]
-			- as default parameters to ENTRYPOINT
-		- CMD command param1 param2
-			- shell form
-	- The main purpose of a CMD is to provide defaults for an executing container. These defaults can include an executable, or they can omit the executable, in which case you must specify an ENTRYPOINT instruction as well.
-	- If CMD is used to provide default arguments for the ENTRYPOINT instruction, both the CMD and ENTRYPOINT instructions should be specified with the JSON array format.
-	- docker run could override the default specified in CMD.
-- ENTRYPOINT
-	- docker run arguments will as the entrypoint’s parameters. not CMD’s override
-	- has two forms
-		- ENTRYPOINT ["executable", "param1", "param2"]
-			- exec form, preferred
-		- ENTRYPOINT command param1 param2
-			- shell form
-	- entrypoint setting can be override by docker run —entrypoint
-- Security
+## ENTRYPOINT
+
+- docker run arguments will as the entrypoint’s parameters. not CMD’s override
+- has two forms
+- ENTRYPOINT ["executable", "param1", "param2"]
+	- exec form, preferred
+- ENTRYPOINT command param1 param2
+	- shell form
+- entrypoint setting can be override by docker run —entrypoint
+
+## Security
 	- https://docs.docker.com/engine/security/security/
 	- use non root user
 	- docker daemon attack surface
 	- kernel security features
+
+## Tips
+
+- difference between `cmd` and `entrypoint`
+- difference between `copy` and `add`
+
+	Basically they are similar, copy files and folder to destination. While ADD has some features (like local-only tar extraction and remote URL support) that are not immediately obvious. Consequently, the best use for ADD is local tar file auto-extraction into the image, as in ADD rootfs.tar.xz /.

categories/devops/kubernetes.md

@@ -703,3 +703,4 @@ k3s is intended to be a fully compliant Kubernetes distribution with the followi
 
 - https://kubernetes.io/docs/concepts/overview/components
 - [Writing a Custom Controller: Extending the Functionality of Your Cluster [I] - Aaron Levy](https://www.youtube.com/watch?v=_BuqPMlXfpE)
+- [kubectl docs](https://kubectl.docs.kubernetes.io/)