Terraform inside of container deletes files - docker

Question

I am finding that docker on my Ubuntu 18.04 host is not retaining files mounted into the container on the host.
Image: hashicorp/terraform
I'm using --mount to bind a directory into the container, the directory is where the terraform config files are stored. I then execute the container which executes terraform which then writes its state files and all the other things.
In 70% of all cases those files don't survive the container. I can see them being created on the host while the container is running, but when the container is done doing its thing the files disappear.
Is that a docker or a terraform issue?
Adding more info:
docker run --mount type=bind,source='/home/david/demo',target=/demo -w /demo -it hashicorp/terraform plan -out tfstate
terraform version
0.11.13
docker version
Client:
Version: 18.09.5
API version: 1.39
Go version: go1.10.8
Git commit: e8ff056
Built: Thu Apr 11 04:43:57 2019
OS/Arch: linux/amd64
Experimental: false
Server: Docker Engine - Community
Engine:
Version: 18.09.5
API version: 1.39 (minimum version 1.12)
Go version: go1.10.8
Git commit: e8ff056
Built: Thu Apr 11 04:10:53 2019
OS/Arch: linux/amd64
Experimental: false

Answer 1

After reading all comments on your question I'm going to sum up how I've test your scenario and my outcome
My docker version:
Docker version 18.09.1, build 4c52b90
Terraform:
Terraform v0.11.13
+ provider.azurerm v1.24.0
I've created a folder which contains my main.tf file with the following configuration:
provider "azurerm" {
version = "=1.24.0"
subscription_id = "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX"
client_id = "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX"
client_secret = "XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX="
tenant_id = "XXXXXXXX-XXXX-XXXX-XXXX-XXXXXXXXXXXX"
}
resource "azurerm_resource_group" "rg" {
name = "testResourceGroup"
location = "westus"
}
I'm behind a proxy so I've executed this the fist time and because I'm connecting to azure I've used init to be able to download the plugin:
docker run --env HTTPS_PROXY="http://myproxyfqdn:port" --rm --mount type=bind,source='/Docker/NFS/terraform',target='/terraform' -w /terraform -it hashicorp/terraform:full init
After this execution the folder on my host refreshed creating .terraform folder with the plugin:
# ls -ltra
-rw-r--r-- 1 root root 759 Apr 23 09:00 main.tf
drwxr-xr-x 3 root root 4096 Apr 23 09:09 .terraform
then I executed the plan with -out parameter that created my plan file for later use:
# docker run --env HTTPS_PROXY="http://myproxyfqdn:port" --rm --mount type=bind,source='/Docker/NFS/terraform',target='/terraform' -w /terraform -it hashicorp/terraform:full plan -out testplan
Refreshing Terraform state in-memory prior to plan...
The refreshed state will be used to calculate this plan, but will not be
persisted to local or remote state storage.
------------------------------------------------------------------------
An execution plan has been generated and is shown below.
Resource actions are indicated with the following symbols:
+ create
Terraform will perform the following actions:
+ azurerm_resource_group.rg
id: <computed>
location: "westus"
name: "testResourceGroup"
tags.%: <computed>
Plan: 1 to add, 0 to change, 0 to destroy.
------------------------------------------------------------------------
That created the plan file on my folder:
# ls -ltra
-rw-r--r-- 1 root root 759 Apr 23 09:00 main.tf
drwxr-xr-x 3 root root 4096 Apr 23 09:09 .terraform
-rw-r--r-- 1 root root 5291 Apr 23 09:11 testplan
And then applying the plan created terraform.tfstate:
# docker run --env HTTPS_PROXY="http://myproxyfqdn:port" --rm --mount type=bind,source='/Docker/NFS/terraform',target='/terraform' -w /terraform -it hashicorp/terraform:full apply testplan
azurerm_resource_group.rg: Creating...
location: "" => "westus"
name: "" => "testResourceGroup"
tags.%: "" => "<computed>"
azurerm_resource_group.rg: Creation complete after 2s (ID: /subscriptions/8d43a801-58b6-4dde-84cc-...c60e6/resourceGroups/testResourceGroup)
Apply complete! Resources: 1 added, 0 changed, 0 destroyed.
Updates on host folder:
# ls -ltra
-rw-r--r-- 1 root root 759 Apr 23 09:00 main.tf
drwxr-xr-x 3 root root 4096 Apr 23 09:09 .terraform
-rw-r--r-- 1 root root 5291 Apr 23 09:11 testplan
-rw-r--r-- 1 root root 3748 Apr 23 09:11 terraform.tfstate
I did not had problems and every execution did update data on the host folder.