verg 0.7.0

Desired-state infrastructure convergence engine

verg

Desired-state infrastructure convergence engine. A fast, stateless alternative to Ansible, built in Rust.

Pre-1.0: verg is under active development. Expect breaking changes between minor versions.

Features

• Fast - pushes a single static binary to each target over SSH; the agent executes locally, so there are no per-task SSH round-trips and no Python dependency on the target.
• Stateless - every run reads actual system state and converges to desired state. No state files are kept on the control host between runs.
• Simple - declare state in TOML files with Jinja2 templating for dynamic values. Strict config validation catches typos before any SSH connection is opened.
• Agent-friendly - --json output, verg schema for machine-readable resource schemas, and structured exit codes make verg easy to drive from scripts and AI agents.
• Secure by default - agent binary is checksum-verified before and after transfer; strict SSH host key checking; config validated locally before touching any target.

Install

# Cargo (crates.io)
cargo install verg

# PyPI
pip install verg

# Homebrew (tap)
brew install rvben/tap/verg

Quick Start

# Scaffold a new project in ./verg/
verg init

# Edit your inventory and desired state
$EDITOR verg/hosts.toml
$EDITOR verg/state/base.toml

# Preview what would change (dry-run, no modifications)
verg diff --targets all

# Apply to all hosts
verg apply --targets all

How It Works

verg (control CLI, runs on your machine) reads TOML state files and your host inventory, builds a host-specific bundle for each target, then pushes a compiled verg-agent binary over SSH. The agent reads the bundle from stdin, checks actual system state, converges each resource to desired state in dependency order, and returns a JSON summary to stdout. The control CLI aggregates results and presents them.

The agent is a static binary with no runtime dependencies. It is checksum-verified before deployment and runs entirely on the target - no per-resource SSH calls from the control host are needed once the agent is running.

Concepts

Project layout

A verg project lives in a directory named verg/ by default (override with --path or the VERG_PATH environment variable). Inside it:

verg/
  hosts.toml       # host inventory
  groups/          # one .toml per group, each with a [vars] table
  state/           # desired-state declarations; loaded in lexicographic order
  files/           # static files referenced by file resources
  templates/       # Jinja2 template files
  .verg/logs/      # structured apply logs (written automatically)

verg init scaffolds this layout with a starter hosts.toml and state/base.toml.

Inventory and selectors

Each host in hosts.toml has these fields:

Field	Required	Default	Description
address	yes	-	IP address or hostname
user	no	"root"	SSH user
port	no	22	SSH port
groups	no	[]	Group memberships
[hosts.NAME.vars]	no	-	Host-specific variables

The --targets flag accepts a selector expression:

Syntax	Meaning
all	Every host
web	Hosts named web or in group web
a,b	Union of selectors a and b
a:b	Intersection (hosts in both a and b)
!x	Exclude x
prod:!db	In group prod but not group db

An unknown selector name is an error (exit code 6). Parentheses are not supported.

State files

State files live in state/ and are loaded in lexicographic order. Each file is a TOML document with this shape:

targets = ["web"]          # optional: limit to hosts in group/name "web"
                           # omit to apply to all hosts

[resource.<type>.<name>]   # one table per resource
property = "value"

A state file with no targets key applies to every host. A state file with targets = ["web"] applies only when the target host belongs to group web or has the name web. Only targets and resource are valid top-level keys; unrecognized keys are rejected by default.

See docs/resources.md for the full resource reference.

Variables and facts

Variables are interpolated using Jinja2 syntax ({{ var }}). Template sources:

Source	Precedence
Host vars ([hosts.NAME.vars])	Highest
Group vars (groups/<g>.toml [vars])	Below host vars
Facts gathered at runtime	Available as fact.arch, fact.os, etc.
Group membership	Available as group.<name>
Inventory context (hosts.*, groups.*)	Lowest

Available facts: fact.arch, fact.hostname, fact.os, fact.os_release, fact.os_version.

String values starting with $env. (e.g. password = "$env.MY_SECRET") are resolved from the environment at build time.

Inline content in a file resource is always interpolated. To interpolate a file loaded via source, set template = true.

cmd resources can register their stdout for use in downstream resources as {{ register.NAME }}. See docs/resources.md for details.

Ordering and handlers

Resources declare dependencies with after = ["type.name", ...]. verg sorts resources into execution layers using Kahn's topological sort; within a layer, resources run in FQN order. A resource whose dependency fails is skipped with "dependency failed".

Resources with handler = true are skipped unless another resource lists their FQN in notify. Handlers run after all normal resources; shorthand notify actions (e.g. reload:nginx, daemon-reload) run after handlers. Each shorthand runs at most once per host per run.

when expressions conditionally skip resources based on facts and group membership (e.g. when = "fact.os == 'ubuntu'").

See docs/resources.md for the full common attributes reference.

Resource Types

Type	Purpose
pkg	Install or remove system packages (apt-get, dnf, pacman - auto-detected)
file	Manage a file's content, permissions, and ownership
directory	Ensure a directory exists with the right permissions and ownership
service	Manage a systemd service's running state and boot enablement
cmd	Run a shell command with an idempotency guard
user	Create or remove a system user
cron	Manage a cron job file in /etc/cron.d/
sysctl	Set a Linux kernel parameter
apt_repo	Add or remove an APT repository with its GPG key
docker_compose	Manage a Docker Compose stack
download	Download a file from a URL, optionally extracting an archive

Complete Example

A minimal nginx setup using pkg, file, and service resources with dependency ordering.

# verg/hosts.toml
[hosts.web1]
address = "192.0.2.10"
user = "root"
groups = ["web"]

[hosts.web1.vars]
http_port = "80"
server_name = "example.com"

# verg/state/nginx.toml
targets = ["web"]

[resource.pkg.nginx]
name = "nginx"
state = "present"

[resource.file.nginx-conf]
path = "/etc/nginx/sites-available/default"
content = """
server {
    listen {{ http_port }};
    server_name {{ server_name }};
    root /var/www/html;
}
"""
mode = "0644"
after = ["pkg.nginx"]
notify = ["reload:nginx"]

[resource.service.nginx]
name = "nginx"
state = "running"
enabled = true
after = ["file.nginx-conf"]

The FQN for each resource is type.name (e.g. pkg.nginx, file.nginx-conf, service.nginx). Every after reference in this example resolves to a resource defined in the same file.

Commands

Command	Key args	Description
verg apply	--targets <TARGETS> (required)	Converge targets to desired state
verg diff	--targets <TARGETS> (default: all), --limit, --offset, --fields	Show what would change without applying
verg check	--targets <TARGETS> (default: all)	Verify targets match desired state (exits 0 when drift found, 1 when all match)
verg schema	-	Print resource type schemas as JSON
verg init	--force	Scaffold a new project directory
verg completions	<bash|fish|zsh|powershell|elvish>	Generate shell completions

apply has no default target. --targets is required to prevent accidental mass applies. Running apply in a non-interactive pipeline without --yes exits with code 5 (confirmation required).

Global Flags

Flag	Default	Description
-o, --output <auto|text|json>	auto	Output format; auto selects JSON when stdout is not a TTY
--json	-	Force JSON output (hidden alias for -o json)
-q, --quiet	-	Suppress per-resource lines; print only the final summary
-y, --yes	-	Proceed when stdin is not a TTY (required for CI/pipelines)
--path <PATH>	./verg	Path to the verg project directory (VERG_PATH)
--parallel <N>	10	Maximum parallel SSH connections
--ssh-config <PATH>	-	Path to SSH config file (VERG_SSH_CONFIG)
--agent-dir <PATH>	-	Directory containing verg-agent binaries per architecture (VERG_AGENT_DIR)
--host-key-checking <yes|accept-new|no>	yes	SSH host key checking policy
--ssh-known-hosts <PATH>	-	Path to a known_hosts file
--skip-agent-checksum	-	Skip agent binary checksum verification (air-gapped or local builds)
--lax-config	-	Downgrade config validation errors (unknown keys/types) to warnings
--timeout <SECONDS>	600	Per-host timeout in seconds

Exit Codes

Code	Name	Meaning
0	SUCCESS	Resources changed or drift detected
1	NOTHING_CHANGED	All resources already in desired state
2	PARTIAL_FAILURE	Some resources failed; others succeeded
3	TOTAL_FAILURE	All resources on all targets failed
4	CONNECTION_ERROR	All failures were SSH connection errors
5	INVALID_CONFIG	Config is invalid, or apply requires --yes (ConfirmationRequired)
6	TARGET_NOT_FOUND	No hosts matched the given target selector
7	INTERNAL_ERROR	Unexpected internal error (I/O or other)
8	CONFLICT	State conflict that cannot be automatically resolved
130	INTERRUPTED	Process received SIGINT (Ctrl-C)

check exits 0 when drift is found and 1 when everything already matches. diff exits 0 on any successful run (even with no changes); only connection or partial failures yield 4 or 2.

Security

verg pushes a compiled agent binary to target hosts and runs it as the configured SSH user (root by default). The agent binary is SHA-256 verified locally before transfer and remotely after transfer using sha256sum -c. SSH host key checking is strict by default (StrictHostKeyChecking=yes). All state files are validated locally before any SSH connection is opened. Resources marked sensitive = true have their payload redacted from output and the apply changelog.

See SECURITY.md for the full threat model, supply chain details, secret handling, and vulnerability reporting.

License

MIT