K
Q

How can I store a binary file in a Kubernetes ConfigMap?

9/9/2016

Can one store a binary file in a Kubernetes ConfigMap and then later read the same content from a volume that mounts this ConfigMap? For example, if directory /etc/mycompany/myapp/config contains binary file keystore.jks, will

kubectl create configmap myapp-config --from-file=/etc/mycompany/myapp/config

include file keystore.jks in ConfigMap myapp-config that can later be mapped to a volume, mounted into a container, and read as a binary file?

For example, given the following pod spec, should keystore.jks be available to myapp at /etc/mycompany/myapp/config/keystore.jks?

apiVersion: v1
kind: Pod
metadata:
  name: myapp
spec:
  containers:
  - name: myapp
    image: mycompany/myapp
    volumeMounts:
    - name: myapp-config
      mountPath: /etc/mycompany/myapp/config

  volumes:
  - name: myapp-config
    configMap:
      name: myapp-config

Kubernetes version details:

derek@derek-HP-EliteOne-800-G1-AiO:~/Documents/platinum/fix/brvm$ kubectl version
Client Version: version.Info{Major:"1", Minor:"3", GitVersion:"v1.3.6", GitCommit:"ae4550cc9c89a593bcda6678df201db1b208133b", GitTreeState:"clean", BuildDate:"2016-08-26T18:13:23Z", GoVersion:"go1.6.2", Compiler:"gc", Platform:"linux/amd64"}
Server Version: version.Info{Major:"1", Minor:"3", GitVersion:"v1.3.6+coreos.0", GitCommit:"f6f0055b8e503cbe5fb7b6f1a2ee37d0f160c1cd", GitTreeState:"clean", BuildDate:"2016-08-29T17:01:01Z", GoVersion:"go1.6.2", Compiler:"gc", Platform:"linux/amd64"}
-- Derek Mahar
configuration
configuration-files
kubernetes

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5 Answers

12/10/2019

I use the secrets for binary files. You can use --from-file

kubectl create secret generic db-user-pass --from-file=./username.txt --from-file=./password.txt
-- de1m
Source: StackOverflow
4/25/2018

Binary ConfigMaps are now supported since Kubernetes version 1.10.0. From the readme notes:

ConfigMap objects now support binary data via a new binaryData field. When using kubectl create configmap --from-file, files containing non-UTF8 data will be placed in this new field in order to preserve the non-UTF8 data. Note that kubectl's --append-hash feature doesn't take binaryData into account. Use of this feature requires 1.10+ apiserver and kubelets. (#57938, @dims)

See the changelog for more details: https://github.com/kubernetes/kubernetes/blob/master/CHANGELOG/CHANGELOG-1.10.md#apps

-- olly___
Source: StackOverflow
9/15/2016

What I would do is encode this file in base64 and then the container that uses decoded to be able to use it

-- Luis Tobon
Source: StackOverflow
9/12/2016

According to Jorgan Liggitt in Kubernetes issue "Enable ConfigMaps to store binary files as well as character files.", Kubernetes 1.3.6 cannot store a binary file in a ConfigMap.

GitHub comment 1:

config maps store data as string, not []byte... not sure I'd expect to be able to put arbitrary binary content in them"

GitHub comment 2:

@liggitt Do ConfigMaps not encode binary content as strings?

they do not, they store strings. base64-encoding could be layered on top with application logic if desired

I subsequently demonstrated that ConfigMaps do not support binary files.

-- Derek Mahar
Source: StackOverflow
12/21/2017

Based on other answers, Base64 works for me (just once)

Steps:

on my workstation

base64 -w 0 cacerts   > cacerts.base64
sha256sum.exe cacerts.base64
keytool.exe  -list -v -keystore cacerts

OpenShift

I connect to openshift and create the config map

oc create configmap cacerts.base64 --from-file=cacerts.base64

deployment configuration

  ...
  template:
    metadata:
      name: mydeployment...
    spec:
      volumes:
        - name: cacerts-volume
          configMap:
            name: cacerts.base64
      containers:
        - name: crg-driver
          command:
            - base64
      args:
            - '--decode'
            - '-w 0'
            - '/opt/axatech/openpaas/certificates/cacerts.base64 >   /opt/axatech/openpaas/certificates/cacerts' #this does not work yet
          env:
            - name: SWARM_JVM_ARGS
              value: >-
                -Djavax.net.ssl.trustStore=/opt/certificates/cacerts.base64
                -Djavax.net.ssl.trustStorePassword=changeit

         volumeMounts:
           - name: cacerts-volume
             mountPath: /opt/certificates

The easiest way to edit/update an existing cacerts is to encode the new cacerts to base64 (with option -w 0) , open it with file editor (ie Notepad), copy the content and paste it via the OpenShift Console UI

https://osconsole.mycloud.something.example/console/project/project-dev/browse/config-maps/cacerts.base64

or in command line

oc edit configmap cacerts.base64

-- Andreas Panagiotidis
Source: StackOverflow