Velocity Template Language (VTL) CLI in Docker

Simple Docker wrapper for the vtl-cli project built by Petr Plavjanik. It uses existing OpenJDK containers on Dockerhub to create a runtime environment for the Java app, increasing portability.

Contact information:
Email: njrusmc@gmail.com
Twitter: @nickrusso42518

Purpose

I create this wrapper mostly for network engineers who interact with Cisco's Digital Network Architecture Center (DNAC) as it uses VTL for its templating system. Not everyone has immediate write access to DNAC, and this tool is meant to eliminate that barrier. However, the tool can be used for any other purpose.

Getting Started

Run the following commands below to get started. Be sure you have docker installed.

# Download the image using your desired version tag
docker pull nickrusso42518/vtlcli-docker:latest

# Create the bind mount directory
mkdir vtlmount/

# Optionally populate vtlmount/ with variable and template files
# See "Using Your Own Files" for more information

# Run a new container, again using your desired version tag
docker container run -it \
  --mount type=bind,source="$(pwd)"/vtlmount,target=/vtlmount \
  nickrusso42518/vtlcli-docker:latest

# You should be in the container shell now

cat sample/README.md

Sample

I've included a simple NTP configuration sample, which you can explore here on GitHub. It generates a Cisco IOS NTP configuration based on some simple variables, using simple VTL constructs like if/else, for, and basic variable substitution.

/ # ./vtl -y sample/vars.yml sample/ntp.vtl
ntp authenticate
no ntp logging
ntp authentication-key 1 md5 secretKey111
ntp authentication-key 2 md5 secretKey222
ntp server 192.0.2.1 key 1
ntp server 192.0.2.2 key 2

Using Your Own Files

Put your template file (.vtl) and variable file (.yml) in your current working directory inside the vtlmount folder you created. When you enter the docker container you can reference them using the following syntax: ./vtl -y vtlmount/my_vars.yml vtlmount/my_template.vtl