Welder

Welder allows you to set up a Linux server with plain shell scripts.

I wrote it out of frustration with Ansible. Ansible is an amazing and powerful tool, but for my needs it's just too much. 90% of the time all I need is to be able to run a shell script on the server, without extra dependencies.

In most basic terms, that's what welder does.

But there's some more.

** NOTE**: if you're looking for the previous version of welder, you'll find it here.

Features

• set up your server with a single command (welder run <playbook> <server>)
• run a set of organized reusable shell scripts
• use simple template syntax ({{ VAR_NAME }}) to substitute config variables

Directory structure

An example directory structure:

 playbook.conf
 config.conf
 firewall
  files
   rules.v4
  firewall.sh
 nginx
  nginx.sh
 system
  files
   10periodic
   50unattended-upgrades
   ssh_key
  system.sh
 website
     files
      site.conf.template
     website.sh

Playbook

Playbook is just a list of modules to execute. Example:

# playbook.conf

system
firewall
nginx
website

Config

Config file:

SITE_DOMAIN = "example.com"
SITE_DIR = "/var/www"

You can reference config variables in your scripts like this:

#!/bin/sh
set -xeu

. ./config.conf

echo $SITE_DOMAIN

Templates

Welder offers simple sed-based templates that interpolate variables in double brackets with values defined in config.

# website/files/nginx-site.conf.template

server {
    listen 80;

    server_name {{ SITE_DOMAIN }};
    root {{ SITE_DIR }}/current/public;
}

Usage

Run the playbook with the following command:

welder run playbook.conf [email protected]

How it works

Welder goes through the modules defined in playbook.conf, copies them to a cache directory, compiles config files and templates, rsyncs the directory to the server. Then it runs the setup script that invokes all *.sh files within the playbook (all scripts will be called with sudo).

Example setup script

# nginx/nginx.sh

# NOTE: sudo isn't necessary because the whole script will be
#       invoked as `sudo nginx/nginx.sh`

set -xeu # 'u' will give you warnings on unbound config variables

add-apt-repository -y ppa:nginx/stable
sapt-get update && apt-get install -y nginx

service nginx start

cp files/nginx.conf /etc/nginx/nginx.conf

# Disable default site
if [ -f /etc/nginx/sites-enabled/default ]; then
  rm /etc/nginx/sites-enabled/default
fi

service nginx restart

Installation

The only dependency required by welder is rsync (which should be pre-installed on your system in most cases).

1. Check out welder into ~/.welder (or whatever location you prefer):

   $ git clone https://github.com/pch/welder.git ~/.welder
   

2. Add ~/.welder/bin to your $PATH for access to the welder command-line utility.

   $ echo 'export PATH="$PATH:$HOME/.welder/bin"' >> ~/.bash_profile
   

   Ubuntu Desktop note: Modify your ~/.bashrc instead of ~/.bash_profile.

   Zsh note: Modify your ~/.zshrc file instead of ~/.bash_profile.

3. Restart your shell so that PATH changes take effect. (Opening a new terminal tab will usually do it.) Now check if welder was set up:

   $  which welder
   /Users/my-user/Code/welder/bin/welder
   

Caveats

Since welder allows you to run anything on the server, you should use it with caution. It won't protect you from screw-ups, like rm -rf "/$undefined_variable".

Use at your own risk.

Alternatives

There's an alternative version of welder (the classic version), re-implemented in Python by @thomas-mc-work.