Shulou(Shulou.com)06/02 Report--

K8s advanced data volume and data persistence volume

Table of contents:

First, the best way to access applications from the outside; second, configure and manage three data volumes and data persistence volumes; fourth, talk about stateful application deployment five K8S security mechanism.

III. Data volumes and data persistent volumes

The background of the data volume generation

Why is there a data volume? the data volume here is not quite the same as the data volume of docker. To put it bluntly, the data volume can help you persist the important data of your pod. If you do not persist, the data temporarily generated in the pod deletion will also be deleted. This is the same no matter in K8s or docker, so both K8s and docker provide this kind of volume related functions. Just to persist the data in your container so that it can be rebuilt or deleted, and the data still exists.

Volume in Kubernetes provides the ability to mount external storage in a container, that is, to deploy K8s' own storage, just like building a distributed storage, just like cloud disk storage in public cloud, so that storage that can be hung outside the cluster can be used in K8s.

To use this kind of storage, pod must define two things:

Pod needs to set the volume source (spec.volume) and mount point (spec.containers.volumeMounts) information before you can use the corresponding Volume.

The best explanation for taking a look at the type of volume is the official:

Let's take a look at what the officials say:

Https://kubernetes.io/docs/concepts/storage/volumes/

The first is the local volume.

For example, the hostPath type and the bind mount type in docker are the types that are mounted directly to the host file.

EmptyDir is such a local volume, which is similar to the volume type

Both of these points are bound to node nodes.

The second is the network data volume.

Such as Nfs, ClusterFs, Ceph, these are external storage that can be mounted to K8s.

The third kind is cloud disk.

Such as AWS, azuredisk

The fourth is the resources of K8s itself.

Such as secret, configmap, downwardAPI

Let's take a look at the local volume first.

Like emptyDir is similar to docker's volume, while docker deletes the container, the data volume will still exist, while emptyDir deletes the container, the data volume will also be lost. Generally, this is only used as a temporary data volume.

Create an empty volume and mount it to the container in Pod. Pod deleting the volume will also be deleted.

Application scenario: data sharing between containers in Pod

EmptyDir Typ

[root@k8s-master demo] # vim emptydir.yamlapiVersion: v1kind: Podmetadata: name: my-podspec: containers:-name: write image: centos command: ["bash", "- c", "for i in {1... 100}; do echo $I > > / data/hello;sleep 1" Done "] volumeMounts:-name: data mountPath: / data-name: read image: centos command: [" bash ","-c " "tail-f / data/hello"] volumeMounts:-name: data mountPath: / data volumes:-name: data emptyDir: {} [root@k8s-master demo] # kubectl create-f emptydir.yaml [root@k8s-master demo] # kubectl get podNAME READY STATUS RESTARTS AGEmy-pod 2 kubectl create 13 67mmypod 1/1 Running 0 3h40mmypod2 1/1 Running 0 3h34mmypod3 0/1 Completed 0 3h6mmypod4 0/1 Completed 0 3hnginx-5ddcc6cb74-lplxl 1/1 Running 0 4h8m [root@k8s-master demo] # kubectl logs my-pod read

Hostpath Typ

Mount a file or directory on the Node file system to a container in Pod.

Application scenario: the container in Pod needs to access the host file

[root@k8s-master demo] # vim hostpath.yaml apiVersion: v1kind: Podmetadata: name: my-pod2spec: containers:-name: busybox image: busybox args:-/ bin/sh-- c-sleep 36000 volumeMounts:-name: data mountPath: / data volumes:-name: data hostPath: path: / tmp type: Directory [root@k8s-master demo] # kubectl create-f hostpath.yaml [root@k8s-master demo ] # kubectl get podNAME READY STATUS RESTARTS AGEmy-pod2 1/1 Running 0 12smypod 1/1 Running 0 4h53mmypod2 1/1 Running 0 4h47mmypod3 0/1 Completed 0 4h27mmypod4 0Running 1 Completed 0 4h22mnginx-5ddcc6cb74-lplxl 1 it my-pod2 shcd 1 Running 0 5h30mweb-67fcf9bf8-mrlhd 1 it my-pod2 shcd 1 Running 0 20m [root@k8s-master demo] # kubectl exec-it my-pod2 shcd / data/ls

The data created here is the same as the data of the node node to which we are assigned. The created data will be updated, the container will be deleted, and the data of the data volume will not be deleted.

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