1. How to clean useless Docker images and containers?
During the process of using Docker, over time, many no longer used or outdated images, stopped containers, useless data volumes, and networks may accumulate in the system, which take up disk space and may lead to performance degradation. Therefore, it is necessary to clean up these resources regularly. Here is how to clean useless Docker images and containers:
Cleaning useless images:
Clean up using Docker command：
docker image prune
This command can delete all dangling images (i.e. mirrors without labels or mirror layers that are no longer used by any container).
If you want to delete all unused images (not just dangling), you can use it with-aOption command:
docker image prune -a
Manually delete：
First, list all images:
docker images
Then according toREPOSITORY、TAGandIMAGE IDInformation, usedocker rmiCommand to delete a specific image:
docker rmi <IMAGE_ID>
Cleaning useless containers:
Delete all stopped containers：
docker container prune
This command deletes all containers that are in a stopped state.
Manually delete：
First, list all containers (including those that are stopped):
docker ps -a
Then according toCONTAINER IDInformation, usedocker rmCommand to delete a specific container:
docker rm <CONTAINER_ID>
In addition, it can also be useddocker volume pruneanddocker network pruneCommands to clean useless data volumes and networks.
2. How to use Docker Swarm for container orchestration and expansion?
Docker Swarm is Docker's built-in cluster management tool, which allows users to form multiple Docker hosts into a cluster and deploy and scale services on that cluster. Here are the basic steps for container orchestration and expansion using Docker Swarm:
Initialize Swarm：
Initialize Swarm on a Docker host, the machine will become the Swarm management node (manager):
docker swarm init
After executing this command, Docker will generate a token for other nodes to join Swarm.
Join Swarm：
On other Docker hosts, join Swarm using the previously generated tokens, these machines can become worker or management nodes:
docker swarm join --token <YOUR_TOKEN> <MANAGER_IP>:<MANAGER_PORT>
Deployment Services：
On the Swarm management node, usedocker stack deployCommand and Compose file deployment service. The Compose file defines the configuration of the service, including the image to be run, environment variables, network, data volume, etc.:
docker stack deploy -c <SERVICE_NAME>
Extended Services：
Extend the service by updating the number of replicas (replicas) of the service. You can specify the number of copies in the Compose file and then usedocker stack deployCommand to re-deploy the service, or usedocker service scaleThe command dynamically adjusts the number of replicas:
docker service scale <SERVICE_NAME>=<DESIRED_REPLICAS>
Management and monitoring：
usedocker serviceCommand group to manage services, such as viewing service details, logs, etc. In addition, Docker's visualization tools (such as Portainer) can be used to more easily manage and monitor Swarm clusters.
3. How to use Kubernetes to manage Docker container clusters?
Kubernetes (K8s) is an open source container orchestration system that supports the automated deployment, scaling and management of containerized applications. Compared to Docker Swarm, Kubernetes offers richer features and higher scalability. Here are the basic steps to manage Docker container clusters using Kubernetes:
Build a Kubernetes cluster：
There are many ways to build Kubernetes clusters, including using kubeadmin, Minikube (local development environment), EKS/AKS/GKE (hosted services of cloud service providers), etc. After the cluster is built, there will be master nodes and multiple worker nodes.
Deploy the application：
In Kubernetes, applications usually run as Pods, a set of tightly coupled containers. Deployment and manage Pods by creating Deployment resources. Deployment defines the expected state of the Pod, and Kubernetes ensures that the actual state is consistent with the expected state.
Service discovery and load balancing：
Use Service resources to expose Pods' network access. Service provides stable network endpoints and can achieve load balancing.
Extended application：
Extend the application by adjusting the number of replicas of the Deployment. Kubernetes will automatically scale or reduce the number of Pods on nodes in the cluster based on resource requirements and scheduling constraints.
Persistent storage：
Use PersistentVolume and PersistentVolumeClaim to manage persistent storage. Pods can access persistent data by mounting Volume.
Configuration and Secret Management：
Use ConfigMap and Secret to manage your application's configuration information and sensitive data. Pods can use these configurations and secrets through environment variables or file mounts.
Monitoring and logging：
Use Kubernetes monitoring tools (such as Metrics Server, Prometheus, etc.) and log collection systems (such as Elasticsearch, Fluentd, etc.) to monitor application performance and log collection.
Access control and security：
Use Kubernetes' authentication, authorization, and network policy capabilities to ensure the security of the cluster. It can define who can access cluster resources and network communication rules between pods.
The above are the basic steps to manage Docker container clusters using Kubernetes. It should be noted that Kubernetes has a relatively steep learning curve, but it provides powerful management and orchestration capabilities for complex large-scale containerized applications.
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