# Reference Documentation

##### Design docs, concept definitions, and references for APIs and CLIs.

- GUIDES
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Version 1.1 Version 1.0

# 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.

Table of Contents

#### docker run

How do I run an nginx container 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"
    replicationcontroller "nginx-app" created
    # expose a port through with a service
    $ kubectl expose rc nginx-app --port=80 --name=nginx-http

With kubectl, we create a replication controller 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 replication controller’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 replication controller 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 replication controller (and it’s pods) you need to run `kubectl delete rc <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 into containers.

#### 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 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 rc nginx-app
    CONTROLLER   CONTAINER(S)   IMAGE(S)   SELECTOR        REPLICAS
    nginx-app    nginx-app      nginx      run=nginx-app   1
    $ kubectl get po
    NAME              READY     STATUS    RESTARTS   AGE
    nginx-app-aualv   1/1       Running   0          16s
    $ kubectl delete rc nginx-app
    NAME              READY     STATUS    RESTARTS   AGE
    nginx-app-aualv   1/1       Running   0          16s
    $ kubectl get po
    NAME      READY     STATUS    RESTARTS   AGE

Notice that we don’t delete the pod directly. With kubectl we want to delete the replication controller that owns the pod. If we delete the pod directly, the replication controller 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