Volumes:
The files in the container exist for a short time. When a container crashes, the files will be lost, but the state after the container restarts is clean; the second problem solves the problem of sharing files between different containers in a Pod.
There are many types of volumes, please check the official documentation for details:roll
1. Volume characteristics:
When a Pod is created, the emptyDir volume is created, and this volume will remain during the Pod run.
Used for data sharing between different containers in Pod.
When a Pod is deleted from a node, the data in the emptyDir volume will also be permanently deleted and will not be saved.
The media used by emptyDir volumes to be stored on that node can be disk or SSD or network storage or memory;
Note that if the media is memory, it will be recorded in the container consumption.
1.2. Official example:
The configuration items are only last three lines, which is relatively simple.
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: /test-webserver
name: test-container
volumeMounts:
- mountPath: /cache
name: cache-volume
volumes:
- name: cache-volume
emptyDir: {}
1.3. Let's make an example:
Step 1: We create a deploy type yaml file we are preparing to use. The general part above is not posted. It mainly depends on the part we want to use. Create two nginx containers and hang the emptyDir volumes under the two containers respectively.
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: /test-webserver
name: test-container
volumeMounts:
- mountPath: /cache
name: cache-volume
volumes:
- name: cache-volume
emptyDir: {}
Step 2: Execute the yaml file to create deploy resources
[root@k8s-master01 ~]# kubectl create -f /dp-cm created [root@k8s-master01 ~]# kubectl get NAME READY UP-TO-DATE AVAILABLE AGE dp-nginx 1/1 1 1 17m [root@k8s-master01 ~]# kubectl get pod NAME READY STATUS RESTARTS AGE dp-nginx-98db5f6df-6g24r 2/2 Running 0 2m40s
Step 3: Create a file in the /opt directory of the nginx container, and then check it in the Chengdu /tmp directory in the redis container to see if it is shared
# Create a file in nginx container[root@k8s-master01 ~]# kubectl exec -ti dp-nginx-98db5f6df-6g24r -c nginx -- bash root@dp-nginx-98db5f6df-6g24r:/# cd /opt/ root@dp-nginx-98db5f6df-6g24r:/opt# touch root@dp-nginx-98db5f6df-6g24r:/opt# ls # Go to the redis container to see if the file is shared[root@k8s-master01 ~]# kubectl exec -ti dp-nginx-98db5f6df-6g24r -c redis -- ls /tmp
Step 4: There is no step 4. From the third step, you can see the files created in the nginx container. You can see them in the redis container. All shared volumes are successful.
2. Volume characteristics:
The hostPath volume can mount files or directories on the host node file system to your Pod.
Note: This method is not recommended for official purposes, but when you need to use hostPath, its scope should be limited to the required files or directories and mounted in a read-only manner.
2.2. Official example:
apiVersion: v1
kind: Pod
metadata:
name: test-pd
spec:
containers:
- image: /test-webserver
name: test-container
volumeMounts:
- mountPath: /test-pd
name: test-volume
volumes:
- name: test-volume
hostPath:
# Directory location on the host path: /data
# This field is optional type: Directory
The type value supported by the hostPath type:
Default is empty: means that no checks are performed before the hostPath volume is installed.
DirectoryOrCreate: If nothing exists on the given path, an empty directory will be created as needed, with permission set to 0755, with the same group and owner information as kubelet.
Directory: A directory that must exist on a given path.
FileOrCreate: If nothing exists on the given path, an empty file will be created there as needed, with permission set to 0644, with the same group and ownership as kubelet.
File: A file that must exist on a given path.
Socket: A UNIX socket that must exist on a given path.
CharDevice: A character device that must exist on a given path.
BlockDevice：BlockDevice
Note: FileOrCreate mode is not responsible for creating the parent directory of the file. If the parent directory of the file to be mounted does not exist, the Pod startup will fail.
2.3. Let's make an example:
Our example is the File type. You can also try other types, and the configuration method is the same
Step 1: From the following example, you can see that the time zone in the container is different from the time zone of our host machine.
[root@k8s-master01 ~]# kubectl exec -ti dp-nginx-98db5f6df-6g24r -c nginx -- cat /etc/timezone Etc/UTC [root@k8s-master01 ~]# cat /etc/timezone Asia/Shanghai
Step 2: Modify the yaml file and then update the deploy copy
spec:
containers:
- image: nginx
name: nginx
volumeMounts:
- mountPath: /opt
name: share-volume
- mountPath: /etc/timezone
name: timezone
- image: redis
name: redis
volumeMounts:
- mountPath: /tmp
name: share-volume
volumes:
- name: share-volume
emptyDir: {}
- name: timezone
hostPath:
path: /etc/timezone # Host path type: File
# Update the copy, pay attention to upper and lowercase, the lowercase I just wrote the file has reported an error[root@k8s-master01 ~]# kubectl replace -f
/dp-nginx replaced
Step 3: Check the container time zone, it is successful and has been modified to shanghai; you can see that the time zone of the host mounted host has been modified, and the time zone of the redis container that is not mounted is still the default
[root@k8s-master01 ~]# kubectl exec dp-nginx-7b456ccf45-8c8fn -c nginx -- cat /etc/timezone Asia/Shanghai [root@k8s-master01 ~]# kubectl exec dp-nginx-7b456ccf45-8c8fn -c redis -- cat /etc/timezone Etc/UTC
The nfs volume can mount NFS (network file system) to your Pod. Unlike emptyDir, the Pod will be deleted while deleting it. The contents of the nfs volume will be saved when deleting the Pod, and the volume will be uninstalled.
However, it is not recommended to use it in production.
I didn't prepare for this example, so I'll talk about how to do it. If you are interested, you can do it yourself.
Step 1: Prepare an NFS server and create a shared directory /data/test
Step 2: Mount the shared directory of nfs into the pod
spec:
containers:
- image: nginx
name: nginx
volumeMounts:
- mountPath: /opt
name: nfs-volume
volumes:
- name: nfs-volume
nfs:
server: 192.168.10.10 #nfs server ip path: /data/test
Step 3: After creating the Pod resource, create a file in the container /opt, check whether it is shared under the nfs server /data/test, and test it in turn. If resource sharing is successful.
For other types of volumes, you can check the official website, and write pv and pvc in the next article!
The above is the detailed content of the use of volumes in the cloud native container kubernetes. For more information about volumes in the cloud native container kubernetes, please follow my other related articles!