IBM Cloud Private and Kubernetes - Coping files

Whilst I have used docker cp numerous times to copy files from a running container to the host ( or vice versa ), I had the need to do the same with a container running in a Pod orchestrated by Kubernetes.

The syntax for Docker is: -

docker cp <<container ID>>:/from-path /to-path

e.g.

docker cp 97ee4c182ece:/opt/ibm/db2/V11.1/java/db2jcc4.jar .

For containers running in Pods via Kubernetes, it's a little different.

The first trick is to inspect the Pod: -

kubectl get pod

NAME                                         READY     STATUS                          RESTARTS   AGE
db2trader-ibm-db2oltp-dev-2298094317-fgn0b   1/1       Running                         0          3h
jenkins-jenkins-662520783-jq60z              1/1       Running                         0          18h
loyalty-level-2196446665-hnsnv               1/1       Running                         0          12m
mqtraader-ibm-mqadvanced-0                   1/1       Running                         0          2h
notification-3317998672-qsgvj                0/1       secrets "openwhisk" not found   0          11m
portfolio-1784192597-588s1                   1/1       Running                         0          11m
redistrader-redis-0                          1/1       Running                         0          2h
redistrader-redis-1                          1/1       Running                         0          2h
redistrader-redis-2                          1/1       Running                         0          2h
stock-quote-2259670618-z0400                 1/1       Running                         0          11m
trader-2151312948-zfvch                      1/1       Running                         0          12m

kubectl describe pod mqtraader-ibm-mqadvanced-0

Name:           mqtraader-ibm-mqadvanced-0
Namespace:      default
Node:           10.0.0.3/10.0.0.3
Start Time:     Wed, 22 Nov 2017 03:07:48 -0800
Labels:         QM_IDENTIFIER=mqtraader
                app=mqtraader-ibm-mqadvanced
                chart=ibm-mqadvanced-server-dev-1.0.1
                controller-revision-hash=mqtraader-ibm-mqadvanced-1107708458
                heritage=Tiller
                release=mqtraader
Annotations:    kubernetes.io/created-by={"kind":"SerializedReference","apiVersion":"v1","reference":{"kind":"StatefulSet","namespace":"default","name":"mqtraader-ibm-mqadvanced","uid":"5f5a8bc6-cf75-11e7-82cf-005056...
                kubernetes.io/psp=default
Status:         Running
IP:             10.1.88.143
Created By:     StatefulSet/mqtraader-ibm-mqadvanced
Controlled By:  StatefulSet/mqtraader-ibm-mqadvanced
Containers:
  qmgr:
    Container ID:   docker://fe7c9127776da0bdea9953dd4d804af17318b019f68aac521222a795d06bf1a3
    Image:          ibmcom/mq:9
    Image ID:       docker-pullable://ibmcom/mq@sha256:76d74d07ccd6fa49297ba01f199ac95e0f89d8c4a068ccb655380c6a5d8aec93
    Ports:          1414/TCP, 9443/TCP
    State:          Running
      Started:      Wed, 22 Nov 2017 03:07:50 -0800
    Ready:          True
    Restart Count:  0
    Limits:
      cpu:     500m
      memory:  512Mi
    Requests:
      cpu:     500m
      memory:  512Mi
    Environment:
      LICENSE:            accept
      MQ_QMGR_NAME:       admin
      MQ_ADMIN_PASSWORD:  <set to the key 'adminPassword' in secret 'mqtraader-ibm-mqadvanced'>  Optional: false
      MQ_APP_PASSWORD:    <set to the key 'appPassword' in secret 'mqtraader-ibm-mqadvanced'>    Optional: false
    Mounts:
      /mnt/mqm from mqtraader-ibm-mqadvanced-mqvol1 (rw)
      /var/run/secrets/kubernetes.io/serviceaccount from default-token-l601r (ro)
Conditions:
  Type           Status
  Initialized    True 
  Ready          True 
  PodScheduled   True 
Volumes:
  mqtraader-ibm-mqadvanced-mqvol1:
    Type:       PersistentVolumeClaim (a reference to a PersistentVolumeClaim in the same namespace)
    ClaimName:  mqtraader-ibm-mqadvanced-mqvol1-mqtraader-ibm-mqadvanced-0
    ReadOnly:   false
  default-token-l601r:
    Type:        Secret (a volume populated by a Secret)
    SecretName:  default-token-l601r
    Optional:    false
QoS Class:       Guaranteed
Node-Selectors:  <none>
Tolerations:     node.alpha.kubernetes.io/notReady:NoExecute for 300s
                 node.alpha.kubernetes.io/unreachable:NoExecute for 300s
Events:          <none>

grabbing the Name and the Namespace, and then using kubectl cp as per the following example: -

kubectl cp default/mqtraader-ibm-mqadvanced-0:/opt/mqm/java/lib/jca/wmq.jmsra.rar ./wmq.jmsra.rar

tar: Removing leading `/' from member names

However, notice one nuance - it's necessary to specify the destination file name as well as the destination path.

Otherwise, if you do this: -

kubectl cp default/mqtraader-ibm-mqadvanced-0:/opt/mqm/java/lib/jca/wmq.jmsra.rar .

you get this: -

tar: Removing leading `/' from member names
error: open .: is a directory

which took me a while to work around.

:-)