Unable to write file from docker run inside a kubernetes pod

I have a docker image that uses a volume to write files:

docker run --rm -v /home/dir:/out/ image:cli args

when I try to run this inside a pod the container exit normally but no file is written.

I don't get it.

The container throw errors if it does not find the volume, for example if I run it without the -v option it throws:

Unhandled Exception: System.IO.DirectoryNotFoundException: Could not find a part of the path '/out/file.txt'.

But I don't have any error from the container.
It finishes like it wrote files, but files do not exist.

I'm quite new to Kubernetes but this is getting me crazy.

Does kubernetes prevent files from being written? or am I missing something obvious?

The whole Kubernetes context is managed by GCP composer-airflow, if it helps...

docker -v: Docker version 17.03.2-ce, build f5ec1e2

edited Nov 15 '18 at 22:34

Rico

27.5k94865

asked Nov 15 '18 at 22:12

donkino

557

hey! so you are running a docker container within a container because pod itself is a container. One thing to make sure he is that, where is the "/home/dir" is it outside your pod or otherwise. then only it can be mounted.

– Narendra
Nov 15 '18 at 22:20

Yeah, that's docker in docker. The /home/dir is inside the pod. Here the pod is the container host right?

– donkino
Nov 15 '18 at 22:25

so is your pod (outer docker) always running. or it exits as well.

– Narendra
Nov 15 '18 at 22:28

Standard Kubernetes does not run Docker-in-Docker (that's generally discouraged); and the Pod is a separate layer from either the host or the container proper. You need to create a volume in the Pod and mount it in the container. This workload doesn't seem like a great match for Kubernetes as you've described it, though.

– David Maze
Nov 15 '18 at 22:54

Thx @DavidMaze . About kubernetes I does not have much of choice, this problem is part of a workflow inside composer-airflow, which run in kubernetes. And our workflow consist in a serie of commands run on different docker containers, each using files generated by the precedent. So I'll give a try to the volume in the pod mounted in the container. Still Idon't get why once inside the pod (and staying in the pod) the files are not created without the container crashing.. (i'll paste an example, it starts to be a lot of containers haha)

– donkino
Nov 15 '18 at 23:33

|
show 1 more comment

I have a docker image that uses a volume to write files:

docker run --rm -v /home/dir:/out/ image:cli args

when I try to run this inside a pod the container exit normally but no file is written.

I don't get it.

The container throw errors if it does not find the volume, for example if I run it without the -v option it throws:

Unhandled Exception: System.IO.DirectoryNotFoundException: Could not find a part of the path '/out/file.txt'.

But I don't have any error from the container.
It finishes like it wrote files, but files do not exist.

I'm quite new to Kubernetes but this is getting me crazy.

Does kubernetes prevent files from being written? or am I missing something obvious?

The whole Kubernetes context is managed by GCP composer-airflow, if it helps...

docker -v: Docker version 17.03.2-ce, build f5ec1e2

edited Nov 15 '18 at 22:34

Rico

27.5k94865

asked Nov 15 '18 at 22:12

donkino

557

hey! so you are running a docker container within a container because pod itself is a container. One thing to make sure he is that, where is the "/home/dir" is it outside your pod or otherwise. then only it can be mounted.

– Narendra
Nov 15 '18 at 22:20

Yeah, that's docker in docker. The /home/dir is inside the pod. Here the pod is the container host right?

– donkino
Nov 15 '18 at 22:25

so is your pod (outer docker) always running. or it exits as well.

– Narendra
Nov 15 '18 at 22:28

Standard Kubernetes does not run Docker-in-Docker (that's generally discouraged); and the Pod is a separate layer from either the host or the container proper. You need to create a volume in the Pod and mount it in the container. This workload doesn't seem like a great match for Kubernetes as you've described it, though.

– David Maze
Nov 15 '18 at 22:54

Thx @DavidMaze . About kubernetes I does not have much of choice, this problem is part of a workflow inside composer-airflow, which run in kubernetes. And our workflow consist in a serie of commands run on different docker containers, each using files generated by the precedent. So I'll give a try to the volume in the pod mounted in the container. Still Idon't get why once inside the pod (and staying in the pod) the files are not created without the container crashing.. (i'll paste an example, it starts to be a lot of containers haha)

– donkino
Nov 15 '18 at 23:33

|
show 1 more comment

I have a docker image that uses a volume to write files:

docker run --rm -v /home/dir:/out/ image:cli args

when I try to run this inside a pod the container exit normally but no file is written.

I don't get it.

The container throw errors if it does not find the volume, for example if I run it without the -v option it throws:

Unhandled Exception: System.IO.DirectoryNotFoundException: Could not find a part of the path '/out/file.txt'.

But I don't have any error from the container.
It finishes like it wrote files, but files do not exist.

I'm quite new to Kubernetes but this is getting me crazy.

Does kubernetes prevent files from being written? or am I missing something obvious?

The whole Kubernetes context is managed by GCP composer-airflow, if it helps...

docker -v: Docker version 17.03.2-ce, build f5ec1e2

edited Nov 15 '18 at 22:34

Rico

27.5k94865

asked Nov 15 '18 at 22:12

donkino

557

I have a docker image that uses a volume to write files:

docker run --rm -v /home/dir:/out/ image:cli args

when I try to run this inside a pod the container exit normally but no file is written.

I don't get it.

The container throw errors if it does not find the volume, for example if I run it without the -v option it throws:

Unhandled Exception: System.IO.DirectoryNotFoundException: Could not find a part of the path '/out/file.txt'.

But I don't have any error from the container.
It finishes like it wrote files, but files do not exist.

I'm quite new to Kubernetes but this is getting me crazy.

Does kubernetes prevent files from being written? or am I missing something obvious?

The whole Kubernetes context is managed by GCP composer-airflow, if it helps...

docker -v: Docker version 17.03.2-ce, build f5ec1e2

docker kubernetes google-kubernetes-engine docker-volume

edited Nov 15 '18 at 22:34

Rico

27.5k94865

asked Nov 15 '18 at 22:12

donkino

557

edited Nov 15 '18 at 22:34

Rico

27.5k94865

asked Nov 15 '18 at 22:12

donkino

557

edited Nov 15 '18 at 22:34

Rico

27.5k94865

edited Nov 15 '18 at 22:34

Rico

27.5k94865

edited Nov 15 '18 at 22:34

Rico

27.5k94865

asked Nov 15 '18 at 22:12

donkino

557

asked Nov 15 '18 at 22:12

donkino

557

asked Nov 15 '18 at 22:12

donkino

557

hey! so you are running a docker container within a container because pod itself is a container. One thing to make sure he is that, where is the "/home/dir" is it outside your pod or otherwise. then only it can be mounted.

– Narendra
Nov 15 '18 at 22:20

Yeah, that's docker in docker. The /home/dir is inside the pod. Here the pod is the container host right?

– donkino
Nov 15 '18 at 22:25

so is your pod (outer docker) always running. or it exits as well.

– Narendra
Nov 15 '18 at 22:28

Standard Kubernetes does not run Docker-in-Docker (that's generally discouraged); and the Pod is a separate layer from either the host or the container proper. You need to create a volume in the Pod and mount it in the container. This workload doesn't seem like a great match for Kubernetes as you've described it, though.

– David Maze
Nov 15 '18 at 22:54

Thx @DavidMaze . About kubernetes I does not have much of choice, this problem is part of a workflow inside composer-airflow, which run in kubernetes. And our workflow consist in a serie of commands run on different docker containers, each using files generated by the precedent. So I'll give a try to the volume in the pod mounted in the container. Still Idon't get why once inside the pod (and staying in the pod) the files are not created without the container crashing.. (i'll paste an example, it starts to be a lot of containers haha)

– donkino
Nov 15 '18 at 23:33

|
show 1 more comment

hey! so you are running a docker container within a container because pod itself is a container. One thing to make sure he is that, where is the "/home/dir" is it outside your pod or otherwise. then only it can be mounted.

– Narendra
Nov 15 '18 at 22:20

Yeah, that's docker in docker. The /home/dir is inside the pod. Here the pod is the container host right?

– donkino
Nov 15 '18 at 22:25

so is your pod (outer docker) always running. or it exits as well.

– Narendra
Nov 15 '18 at 22:28

Standard Kubernetes does not run Docker-in-Docker (that's generally discouraged); and the Pod is a separate layer from either the host or the container proper. You need to create a volume in the Pod and mount it in the container. This workload doesn't seem like a great match for Kubernetes as you've described it, though.

– David Maze
Nov 15 '18 at 22:54

Thx @DavidMaze . About kubernetes I does not have much of choice, this problem is part of a workflow inside composer-airflow, which run in kubernetes. And our workflow consist in a serie of commands run on different docker containers, each using files generated by the precedent. So I'll give a try to the volume in the pod mounted in the container. Still Idon't get why once inside the pod (and staying in the pod) the files are not created without the container crashing.. (i'll paste an example, it starts to be a lot of containers haha)

– donkino
Nov 15 '18 at 23:33

hey! so you are running a docker container within a container because pod itself is a container. One thing to make sure he is that, where is the "/home/dir" is it outside your pod or otherwise. then only it can be mounted.

– Narendra
Nov 15 '18 at 22:20

Yeah, that's docker in docker. The /home/dir is inside the pod. Here the pod is the container host right?

– donkino
Nov 15 '18 at 22:25

so is your pod (outer docker) always running. or it exits as well.

– Narendra
Nov 15 '18 at 22:28

Standard Kubernetes does not run Docker-in-Docker (that's generally discouraged); and the Pod is a separate layer from either the host or the container proper. You need to create a volume in the Pod and mount it in the container. This workload doesn't seem like a great match for Kubernetes as you've described it, though.

– David Maze
Nov 15 '18 at 22:54

Thx @DavidMaze . About kubernetes I does not have much of choice, this problem is part of a workflow inside composer-airflow, which run in kubernetes. And our workflow consist in a serie of commands run on different docker containers, each using files generated by the precedent. So I'll give a try to the volume in the pod mounted in the container. Still Idon't get why once inside the pod (and staying in the pod) the files are not created without the container crashing.. (i'll paste an example, it starts to be a lot of containers haha)

– donkino
Nov 15 '18 at 23:33

|
show 1 more comment

2 Answers
2

active

oldest

votes

If you want to have that behavior in Kubernetes you can use a hostPath volume.

Essentially you specify it in your pod spec and then the volume is mounted on the node where your pod runs and then the file should be there in the node after the pod exits.

apiVersion: v1

kind: Pod

metadata:

  name: test-pd

spec:

  containers:

  - image: image:cli

    name: test-container

    volumeMounts:

    - mountPath: /home/dir

      name: test-volume

  volumes:

  - name: test-volume

    hostPath:

      path: /out

      type: Directory

answered Nov 15 '18 at 22:38

Rico

27.5k94865

Thx, I'll try that. But problem is the file doesn't exist while the pod is alive. I mean I enter the pod (via kubectl exec - it pod - - bin/bash), run the container, and no files...

– donkino
Nov 15 '18 at 22:51

You may not be able to write to /out

– Rico
Nov 15 '18 at 22:54

Hey! I was using an emptyDir to mount /home/dir. I changed that to an hostPath and it worked! Thanks so much :)

– donkino
Nov 16 '18 at 14:57

add a comment |

when I try to run this inside a pod the container exit normally but no file is written

First of all, there is no need to run the docker run command inside the pod :). A spec file (yaml) should be written for the pod and kubernetes will run the container in the pod using docker for you. Ideally, you don't need to run docker commands when using kubernetes (unless you are debugging docker-related issues).

This link has useful kubectl commands for docker users.

If you are used to docker-compose, refer Kompose to go from docker-compose to kubernetes:

https://github.com/kubernetes/kompose

http://kompose.io

Some options to mount a directory on the host as a volume inside the container in kubernetes:

hostPath

emptyDir

configMap

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

add a comment |

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2 Answers
2

active

oldest

votes

2 Answers
2

active

oldest

votes

If you want to have that behavior in Kubernetes you can use a hostPath volume.

Essentially you specify it in your pod spec and then the volume is mounted on the node where your pod runs and then the file should be there in the node after the pod exits.

apiVersion: v1

kind: Pod

metadata:

  name: test-pd

spec:

  containers:

  - image: image:cli

    name: test-container

    volumeMounts:

    - mountPath: /home/dir

      name: test-volume

  volumes:

  - name: test-volume

    hostPath:

      path: /out

      type: Directory

answered Nov 15 '18 at 22:38

Rico

27.5k94865

Thx, I'll try that. But problem is the file doesn't exist while the pod is alive. I mean I enter the pod (via kubectl exec - it pod - - bin/bash), run the container, and no files...

– donkino
Nov 15 '18 at 22:51

You may not be able to write to /out

– Rico
Nov 15 '18 at 22:54

Hey! I was using an emptyDir to mount /home/dir. I changed that to an hostPath and it worked! Thanks so much :)

– donkino
Nov 16 '18 at 14:57

add a comment |

If you want to have that behavior in Kubernetes you can use a hostPath volume.

Essentially you specify it in your pod spec and then the volume is mounted on the node where your pod runs and then the file should be there in the node after the pod exits.

apiVersion: v1

kind: Pod

metadata:

  name: test-pd

spec:

  containers:

  - image: image:cli

    name: test-container

    volumeMounts:

    - mountPath: /home/dir

      name: test-volume

  volumes:

  - name: test-volume

    hostPath:

      path: /out

      type: Directory

answered Nov 15 '18 at 22:38

Rico

27.5k94865

Thx, I'll try that. But problem is the file doesn't exist while the pod is alive. I mean I enter the pod (via kubectl exec - it pod - - bin/bash), run the container, and no files...

– donkino
Nov 15 '18 at 22:51

You may not be able to write to /out

– Rico
Nov 15 '18 at 22:54

Hey! I was using an emptyDir to mount /home/dir. I changed that to an hostPath and it worked! Thanks so much :)

– donkino
Nov 16 '18 at 14:57

add a comment |

If you want to have that behavior in Kubernetes you can use a hostPath volume.

Essentially you specify it in your pod spec and then the volume is mounted on the node where your pod runs and then the file should be there in the node after the pod exits.

apiVersion: v1

kind: Pod

metadata:

  name: test-pd

spec:

  containers:

  - image: image:cli

    name: test-container

    volumeMounts:

    - mountPath: /home/dir

      name: test-volume

  volumes:

  - name: test-volume

    hostPath:

      path: /out

      type: Directory

answered Nov 15 '18 at 22:38

Rico

27.5k94865

If you want to have that behavior in Kubernetes you can use a hostPath volume.

Essentially you specify it in your pod spec and then the volume is mounted on the node where your pod runs and then the file should be there in the node after the pod exits.

apiVersion: v1

kind: Pod

metadata:

  name: test-pd

spec:

  containers:

  - image: image:cli

    name: test-container

    volumeMounts:

    - mountPath: /home/dir

      name: test-volume

  volumes:

  - name: test-volume

    hostPath:

      path: /out

      type: Directory

answered Nov 15 '18 at 22:38

Rico

27.5k94865

answered Nov 15 '18 at 22:38

Rico

27.5k94865

answered Nov 15 '18 at 22:38

Rico

27.5k94865

answered Nov 15 '18 at 22:38

Rico

27.5k94865

Thx, I'll try that. But problem is the file doesn't exist while the pod is alive. I mean I enter the pod (via kubectl exec - it pod - - bin/bash), run the container, and no files...

– donkino
Nov 15 '18 at 22:51

You may not be able to write to /out

– Rico
Nov 15 '18 at 22:54

Hey! I was using an emptyDir to mount /home/dir. I changed that to an hostPath and it worked! Thanks so much :)

– donkino
Nov 16 '18 at 14:57

add a comment |

Thx, I'll try that. But problem is the file doesn't exist while the pod is alive. I mean I enter the pod (via kubectl exec - it pod - - bin/bash), run the container, and no files...

– donkino
Nov 15 '18 at 22:51

You may not be able to write to /out

– Rico
Nov 15 '18 at 22:54

Hey! I was using an emptyDir to mount /home/dir. I changed that to an hostPath and it worked! Thanks so much :)

– donkino
Nov 16 '18 at 14:57

Thx, I'll try that. But problem is the file doesn't exist while the pod is alive. I mean I enter the pod (via kubectl exec - it pod - - bin/bash), run the container, and no files...

– donkino
Nov 15 '18 at 22:51

You may not be able to write to /out

– Rico
Nov 15 '18 at 22:54

Hey! I was using an emptyDir to mount /home/dir. I changed that to an hostPath and it worked! Thanks so much :)

– donkino
Nov 16 '18 at 14:57

add a comment |

when I try to run this inside a pod the container exit normally but no file is written

This link has useful kubectl commands for docker users.

If you are used to docker-compose, refer Kompose to go from docker-compose to kubernetes:

https://github.com/kubernetes/kompose

http://kompose.io

Some options to mount a directory on the host as a volume inside the container in kubernetes:

hostPath

emptyDir

configMap

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

add a comment |

when I try to run this inside a pod the container exit normally but no file is written

This link has useful kubectl commands for docker users.

If you are used to docker-compose, refer Kompose to go from docker-compose to kubernetes:

https://github.com/kubernetes/kompose

http://kompose.io

Some options to mount a directory on the host as a volume inside the container in kubernetes:

hostPath

emptyDir

configMap

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

add a comment |

when I try to run this inside a pod the container exit normally but no file is written

This link has useful kubectl commands for docker users.

If you are used to docker-compose, refer Kompose to go from docker-compose to kubernetes:

https://github.com/kubernetes/kompose

http://kompose.io

Some options to mount a directory on the host as a volume inside the container in kubernetes:

hostPath

emptyDir

configMap

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

when I try to run this inside a pod the container exit normally but no file is written

This link has useful kubectl commands for docker users.

If you are used to docker-compose, refer Kompose to go from docker-compose to kubernetes:

https://github.com/kubernetes/kompose

http://kompose.io

Some options to mount a directory on the host as a volume inside the container in kubernetes:

hostPath

emptyDir

configMap

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

answered Nov 16 '18 at 3:01

Vikram Hosakote

1,083311

add a comment |

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