274 lines
9.8 KiB
Markdown
274 lines
9.8 KiB
Markdown
---
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---
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In this doc, we introduce the Kubernetes command line for interacting with the api to docker-cli users. The tool, kubectl, is designed to be familiar to docker-cli users but there are a few necessary differences. Each section of this doc highlights a docker subcommand explains the kubectl equivalent.
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* TOC
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{:toc}
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#### docker run
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How do I run an nginx Deployment and expose it to the world? Checkout [kubectl run](/docs/user-guide/kubectl/kubectl_run).
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With docker:
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```shell
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$ docker run -d --restart=always -e DOMAIN=cluster --name nginx-app -p 80:80 nginx
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a9ec34d9878748d2f33dc20cb25c714ff21da8d40558b45bfaec9955859075d0
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$ docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a9ec34d98787 nginx "nginx -g 'daemon of 2 seconds ago Up 2 seconds 0.0.0.0:80->80/tcp, 443/tcp nginx-app
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```
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With kubectl:
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```shell
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# start the pod running nginx
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$ kubectl run --image=nginx nginx-app --port=80 --env="DOMAIN=cluster"
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deployment "nginx-app" created
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```
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`kubectl run` creates a Deployment named "nginx" on Kubernetes cluster >= v1.2. If you are running older versions, it creates replication controllers instead.
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If you want to obtain the old behavior, use `--generator=run/v1` to create replication controllers. See [`kubectl run`](/docs/user-guide/kubectl/kubectl_run/) for more details.
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Note that `kubectl` commands will print the type and name of the resource created or mutated, which can then be used in subsequent commands. Now, we can expose a new Service with the deployment created above:
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```shell
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# expose a port through with a service
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$ kubectl expose deployment nginx-app --port=80 --name=nginx-http
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service "nginx-http" exposed
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```
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With kubectl, we create a [Deployment](/docs/user-guide/deployments) which will make sure that N pods are running nginx (where N is the number of replicas stated in the spec, which defaults to 1). We also create a [service](/docs/user-guide/services) with a selector that matches the Deployment's selector. See the [Quick start](/docs/user-guide/quick-start) for more information.
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By default images are run in the background, similar to `docker run -d ...`, if you want to run things in the foreground, use:
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```shell
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kubectl run [-i] [--tty] --attach <name> --image=<image>
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```
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Unlike `docker run ...`, if `--attach` is specified, we attach to `stdin`, `stdout` and `stderr`, there is no ability to control which streams are attached (`docker -a ...`).
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Because we start a Deployment for your container, it will be restarted if you terminate the attached process (e.g. `ctrl-c`), this is different than `docker run -it`.
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To destroy the Deployment (and its pods) you need to run `kubectl delete deployment <name>`
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#### docker ps
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How do I list what is currently running? Checkout [kubectl get](/docs/user-guide/kubectl/kubectl_get).
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With docker:
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```shell
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$ docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a9ec34d98787 nginx "nginx -g 'daemon of About an hour ago Up About an hour 0.0.0.0:80->80/tcp, 443/tcp nginx-app
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```
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With kubectl:
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```shell
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$ kubectl get po
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NAME READY STATUS RESTARTS AGE
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nginx-app-5jyvm 1/1 Running 0 1h
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```
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#### docker attach
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How do I attach to a process that is already running in a container? Checkout [kubectl attach](/docs/user-guide/kubectl/kubectl_attach)
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With docker:
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```shell
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$ docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a9ec34d98787 nginx "nginx -g 'daemon of 8 minutes ago Up 8 minutes 0.0.0.0:80->80/tcp, 443/tcp nginx-app
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$ docker attach -it a9ec34d98787
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...
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```
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With kubectl:
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```shell
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$ kubectl get pods
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NAME READY STATUS RESTARTS AGE
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nginx-app-5jyvm 1/1 Running 0 10m
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$ kubectl attach -it nginx-app-5jyvm
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...
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```
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#### docker exec
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How do I execute a command in a container? Checkout [kubectl exec](/docs/user-guide/kubectl/kubectl_exec).
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With docker:
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```shell
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$ docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a9ec34d98787 nginx "nginx -g 'daemon of 8 minutes ago Up 8 minutes 0.0.0.0:80->80/tcp, 443/tcp nginx-app
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$ docker exec a9ec34d98787 cat /etc/hostname
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a9ec34d98787
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```
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With kubectl:
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```shell
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$ kubectl get po
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NAME READY STATUS RESTARTS AGE
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nginx-app-5jyvm 1/1 Running 0 10m
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$ kubectl exec nginx-app-5jyvm -- cat /etc/hostname
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nginx-app-5jyvm
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```
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What about interactive commands?
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With docker:
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```shell
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$ docker exec -ti a9ec34d98787 /bin/sh
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# exit
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```
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With kubectl:
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```shell
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$ kubectl exec -ti nginx-app-5jyvm -- /bin/sh
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# exit
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```
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For more information see [Getting into containers](/docs/user-guide/getting-into-containers).
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#### docker logs
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How do I follow stdout/stderr of a running process? Checkout [kubectl logs](/docs/user-guide/kubectl/kubectl_logs).
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With docker:
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```shell
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$ docker logs -f a9e
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192.168.9.1 - - [14/Jul/2015:01:04:02 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.35.0" "-"
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192.168.9.1 - - [14/Jul/2015:01:04:03 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.35.0" "-"
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```
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With kubectl:
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```shell
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$ kubectl logs -f nginx-app-zibvs
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10.240.63.110 - - [14/Jul/2015:01:09:01 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
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10.240.63.110 - - [14/Jul/2015:01:09:02 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
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```
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Now's a good time to mention slight difference between pods and containers; by default pods will not terminate if their processes exit. Instead it will restart the process. This is similar to the docker run option `--restart=always` with one major difference. In docker, the output for each invocation of the process is concatenated but for Kubernetes, each invocation is separate. To see the output from a previous run in Kubernetes, do this:
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```shell
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$ kubectl logs --previous nginx-app-zibvs
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10.240.63.110 - - [14/Jul/2015:01:09:01 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
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10.240.63.110 - - [14/Jul/2015:01:09:02 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
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```
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See [Logging](/docs/user-guide/logging) for more information.
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#### docker stop and docker rm
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How do I stop and delete a running process? Checkout [kubectl delete](/docs/user-guide/kubectl/kubectl_delete).
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With docker
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```shell
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$ docker ps
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CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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a9ec34d98787 nginx "nginx -g 'daemon of 22 hours ago Up 22 hours 0.0.0.0:80->80/tcp, 443/tcp nginx-app
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$ docker stop a9ec34d98787
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a9ec34d98787
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$ docker rm a9ec34d98787
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a9ec34d98787
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```
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With kubectl:
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```shell
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$ kubectl get deployment nginx-app
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NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
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nginx-app 1 1 1 1 2m
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$ kubectl get po -l run=nginx-app
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NAME READY STATUS RESTARTS AGE
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nginx-app-2883164633-aklf7 1/1 Running 0 2m
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$ kubectl delete deployment nginx-app
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deployment "nginx-app" deleted
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$ kubectl get po -l run=nginx-app
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# Return nothing
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```
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Notice that we don't delete the pod directly. With kubectl we want to delete the Deployment that owns the pod. If we delete the pod directly, the Deployment will recreate the pod.
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#### docker login
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There is no direct analog of `docker login` in kubectl. If you are interested in using Kubernetes with a private registry, see [Using a Private Registry](/docs/user-guide/images/#using-a-private-registry).
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#### docker version
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How do I get the version of my client and server? Checkout [kubectl version](/docs/user-guide/kubectl/kubectl_version).
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With docker:
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```shell
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$ docker version
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Client version: 1.7.0
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Client API version: 1.19
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Go version (client): go1.4.2
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Git commit (client): 0baf609
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OS/Arch (client): linux/amd64
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Server version: 1.7.0
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Server API version: 1.19
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Go version (server): go1.4.2
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Git commit (server): 0baf609
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OS/Arch (server): linux/amd64
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```
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With kubectl:
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```shell
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$ kubectl version
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Client Version: version.Info{Major:"0", Minor:"20.1", GitVersion:"v0.20.1", GitCommit:"", GitTreeState:"not a git tree"}
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Server Version: version.Info{Major:"0", Minor:"21+", GitVersion:"v0.21.1-411-g32699e873ae1ca-dirty", GitCommit:"32699e873ae1caa01812e41de7eab28df4358ee4", GitTreeState:"dirty"}
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```
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#### docker info
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How do I get miscellaneous info about my environment and configuration? Checkout [kubectl cluster-info](/docs/user-guide/kubectl/kubectl_cluster-info).
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With docker:
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```shell
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$ docker info
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Containers: 40
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Images: 168
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Storage Driver: aufs
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Root Dir: /usr/local/google/docker/aufs
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Backing Filesystem: extfs
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Dirs: 248
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Dirperm1 Supported: false
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Execution Driver: native-0.2
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Logging Driver: json-file
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Kernel Version: 3.13.0-53-generic
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Operating System: Ubuntu 14.04.2 LTS
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CPUs: 12
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Total Memory: 31.32 GiB
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Name: k8s-is-fun.mtv.corp.google.com
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ID: ADUV:GCYR:B3VJ:HMPO:LNPQ:KD5S:YKFQ:76VN:IANZ:7TFV:ZBF4:BYJO
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WARNING: No swap limit support
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```
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With kubectl:
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```shell
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$ kubectl cluster-info
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Kubernetes master is running at https://108.59.85.141
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KubeDNS is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/kube-dns
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KubeUI is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/kube-ui
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Grafana is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/monitoring-grafana
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Heapster is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/monitoring-heapster
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InfluxDB is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/monitoring-influxdb
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```
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