kubectl for Docker Users
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.
- docker run
- docker ps
- docker attach
- docker exec
- docker logs
- docker stop and docker rm
- docker login
- docker version
- docker info
docker run
How do I run an nginx Deployment and expose it to the world? Checkout kubectl run.
With docker:
$ docker run -d --restart=always -e DOMAIN=cluster --name nginx-app -p 80:80 nginx
a9ec34d9878748d2f33dc20cb25c714ff21da8d40558b45bfaec9955859075d0
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a9ec34d98787 nginx "nginx -g 'daemon of 2 seconds ago Up 2 seconds 0.0.0.0:80->80/tcp, 443/tcp nginx-app
With kubectl:
# start the pod running nginx
$ kubectl run --image=nginx nginx-app --port=80 --env="DOMAIN=cluster"
deployment "nginx-app" created
kubectl run creates a Deployment named “nginx-app” on Kubernetes cluster >= v1.2. If you are running older versions, it creates replication controllers instead.
If you want to obtain the old behavior, use --generator=run/v1 to create replication controllers. See kubectl run for more details.
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:
# expose a port through with a service
$ kubectl expose deployment nginx-app --port=80 --name=nginx-http
service "nginx-http" exposed
With kubectl, we create a Deployment 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 with a selector that matches the Deployment’s selector. See the Quick start for more information.
By default images are run in the background, similar to docker run -d ..., if you want to run things in the foreground, use:
kubectl run [-i] [--tty] --attach <name> --image=<image>
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 ...).
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.
To destroy the Deployment (and its pods) you need to run kubectl delete deployment <name>
docker ps
How do I list what is currently running? Checkout kubectl get.
With docker:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
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
With kubectl:
$ kubectl get po
NAME READY STATUS RESTARTS AGE
nginx-app-5jyvm 1/1 Running 0 1h
docker attach
How do I attach to a process that is already running in a container? Checkout kubectl attach
With docker:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a9ec34d98787 nginx "nginx -g 'daemon of 8 minutes ago Up 8 minutes 0.0.0.0:80->80/tcp, 443/tcp nginx-app
$ docker attach -it a9ec34d98787
...
With kubectl:
$ kubectl get pods
NAME READY STATUS RESTARTS AGE
nginx-app-5jyvm 1/1 Running 0 10m
$ kubectl attach -it nginx-app-5jyvm
...
docker exec
How do I execute a command in a container? Checkout kubectl exec.
With docker:
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a9ec34d98787 nginx "nginx -g 'daemon of 8 minutes ago Up 8 minutes 0.0.0.0:80->80/tcp, 443/tcp nginx-app
$ docker exec a9ec34d98787 cat /etc/hostname
a9ec34d98787
With kubectl:
$ kubectl get po
NAME READY STATUS RESTARTS AGE
nginx-app-5jyvm 1/1 Running 0 10m
$ kubectl exec nginx-app-5jyvm -- cat /etc/hostname
nginx-app-5jyvm
What about interactive commands?
With docker:
$ docker exec -ti a9ec34d98787 /bin/sh
# exit
With kubectl:
$ kubectl exec -ti nginx-app-5jyvm -- /bin/sh
# exit
For more information see Getting a Shell to a Running Container.
docker logs
How do I follow stdout/stderr of a running process? Checkout kubectl logs.
With docker:
$ docker logs -f a9e
192.168.9.1 - - [14/Jul/2015:01:04:02 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.35.0" "-"
192.168.9.1 - - [14/Jul/2015:01:04:03 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.35.0" "-"
With kubectl:
$ kubectl logs -f nginx-app-zibvs
10.240.63.110 - - [14/Jul/2015:01:09:01 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
10.240.63.110 - - [14/Jul/2015:01:09:02 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
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:
$ kubectl logs --previous nginx-app-zibvs
10.240.63.110 - - [14/Jul/2015:01:09:01 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
10.240.63.110 - - [14/Jul/2015:01:09:02 +0000] "GET / HTTP/1.1" 200 612 "-" "curl/7.26.0" "-"
See Logging and Monitoring Cluster Activity for more information.
docker stop and docker rm
How do I stop and delete a running process? Checkout kubectl delete.
With docker
$ docker ps
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
a9ec34d98787 nginx "nginx -g 'daemon of 22 hours ago Up 22 hours 0.0.0.0:80->80/tcp, 443/tcp nginx-app
$ docker stop a9ec34d98787
a9ec34d98787
$ docker rm a9ec34d98787
a9ec34d98787
With kubectl:
$ kubectl get deployment nginx-app
NAME DESIRED CURRENT UP-TO-DATE AVAILABLE AGE
nginx-app 1 1 1 1 2m
$ kubectl get po -l run=nginx-app
NAME READY STATUS RESTARTS AGE
nginx-app-2883164633-aklf7 1/1 Running 0 2m
$ kubectl delete deployment nginx-app
deployment "nginx-app" deleted
$ kubectl get po -l run=nginx-app
# Return nothing
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.
docker login
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.
docker version
How do I get the version of my client and server? Checkout kubectl version.
With docker:
$ docker version
Client version: 1.7.0
Client API version: 1.19
Go version (client): go1.4.2
Git commit (client): 0baf609
OS/Arch (client): linux/amd64
Server version: 1.7.0
Server API version: 1.19
Go version (server): go1.4.2
Git commit (server): 0baf609
OS/Arch (server): linux/amd64
With kubectl:
$ kubectl version
Client Version: version.Info{Major:"0", Minor:"20.1", GitVersion:"v0.20.1", GitCommit:"", GitTreeState:"not a git tree"}
Server Version: version.Info{Major:"0", Minor:"21+", GitVersion:"v0.21.1-411-g32699e873ae1ca-dirty", GitCommit:"32699e873ae1caa01812e41de7eab28df4358ee4", GitTreeState:"dirty"}
docker info
How do I get miscellaneous info about my environment and configuration? Checkout kubectl cluster-info.
With docker:
$ docker info
Containers: 40
Images: 168
Storage Driver: aufs
Root Dir: /usr/local/google/docker/aufs
Backing Filesystem: extfs
Dirs: 248
Dirperm1 Supported: false
Execution Driver: native-0.2
Logging Driver: json-file
Kernel Version: 3.13.0-53-generic
Operating System: Ubuntu 14.04.2 LTS
CPUs: 12
Total Memory: 31.32 GiB
Name: k8s-is-fun.mtv.corp.google.com
ID: ADUV:GCYR:B3VJ:HMPO:LNPQ:KD5S:YKFQ:76VN:IANZ:7TFV:ZBF4:BYJO
WARNING: No swap limit support
With kubectl:
$ kubectl cluster-info
Kubernetes master is running at https://108.59.85.141
KubeDNS is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/kube-dns
KubeUI is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/kube-ui
Grafana is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/monitoring-grafana
Heapster is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/monitoring-heapster
InfluxDB is running at https://108.59.85.141/api/v1/proxy/namespaces/kube-system/services/monitoring-influxdb