Using Artifact Stanza to Copy Files into Docker Container

Introduction

This how-do is to demonstrate using artifact stanza with mode=”file” to copy a file from an external source to a specific folder in a docker container.

Problem

For operator who desires to keep the existing files on the target directory, they would need to utilize an existing allocation directory /local without having to map additional mount point inside the docker container.

Solution

In this test image, it demonstrates using /usr/share/ as the target directory in the container :

    task "redis" {
      driver = "docker"
      config {
        image = "redis:3.2"
        port_map {
          db = 6379
        }
        volumes = ["local/ojdbc8.jar:/usr/share/ojdbc8.jar"]
      }
      artifact {
        source = "https://repo1.maven.org/maven2/com/oracle/database/jdbc/ojdbc8/19.6.0.0/ojdbc8-19.6.0.0.jar"
        destination = "local/ojdbc8.jar"
        mode = "file"
      }

root@ip-172-31-40-48:~# nomad alloc exec e4a /bin/bash
root@0a6ec15b292c:~# ls /usr/share/
adduser          common-licenses  doc-base  keyrings  menu         perl5
base-files       debconf          dpkg      libc-bin  misc         pixmaps
base-passwd      debianutils      gcc-6     lintian   ojdbc8.jar   tabset
bash-completion  dict             gdb       locale    pam          terminfo
bug              doc              info      man       pam-configs  zoneinfo

Notice that the file ojdbc8.jar showed up with previously existing files in that target directory /usr/share as intended for in this example.

Essentially you are creating a mount point in the container like below so the parallel files are visible to you instead of being mounted over like previous example shown last week:

        "Mounts": [                                                                                                                            
            {                                                                                                                                  
                "Type": "bind",                                                                                                                
                "Source": "/opt/nomad/data/alloc/e4a756ef-71c6-9206-a28d-ee962fe2fc46/redis/local/ojdbc8.jar",                                                                                                                              
                "Destination": "/usr/share/ojdbc8.jar",                                                                                        
                "Mode": "",                                                                                                                    
                "RW": true,                                                                                                                    
                "Propagation": "rprivate"                                                                                                      
            },