Update step-by-step send payment guide with docker

[Euler-B]

Change Description

This PR is the result of a step-by-step validation of the Send Payment Guide with Docker. After encountering several issues with the original workflow, I conducted a deep dive into the underlying failures, testing all available options described in the guide and researching related documentation.

The result is an updated, functional guide that works out-of-the-box. Key changes include:

• Simnet Focus: This update specifically focuses on Simnet due to its simplicity in block generation. It provides a seamless environment for new developers to test LND payment commands instantly without external dependencies.

• Removal of Obsolete Resources: I have removed the section regarding the faucet.lightning.community.web , as it is currently offline.

• Signet Considerations: I've clarified that obtaining funds via Signet can be time-consuming, as it depends on available computing power for mining/proof-of-work requirements, which might frustrate newcomers.

This guide now serves as a reliable and modern reference for anyone’s first encounter with the LND payment flow..

Steps to Test

Follow the instructions provided in the updated docker/README.md.

Pull Request Checklist

Testing

• Your PR passes all CI checks.
• Tests covering the positive and negative (error paths) are included.
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• The change obeys the Code Documentation and Commenting guidelines, and lines wrap at 80.
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• Any new lncli commands have appropriate tags in the comments for the rpc in the proto file.
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[gemini-code-assist]

Summary of Changes

Hello @Euler-B, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request delivers a thoroughly validated and updated step-by-step guide for setting up and sending payments using LND with Docker. It resolves previous workflow issues, ensuring a reliable and out-of-the-box experience for users interacting with the LND payment flow. The changes encompass dependency updates, command syntax modernization, and configuration adjustments across the Docker environment for LND and BTCD.

Highlights

• docker/README.md Updates: The guide for sending payments with Docker has been significantly revised, including updated Docker prerequisites, modern docker compose command syntax, and the removal of an outdated "Connect to faucet lightning node" section.
• btcd Dockerfile Enhancements: The btcd Dockerfile now uses a newer Go version (1.25.3), updates the BTCD_VERSION to v0.24.2, specifies alpine:3.20 as the base image, corrects segnet to signet in comments, and includes a HEALTHCHECK for the btcd service.
• docker-compose.yml Modernization: The deprecated version: '2' declaration has been removed, and the btcd service build now explicitly references its Dockerfile.
• lnd Startup Script Adjustments: The start-lnd.sh script has been updated to remove the --$CHAIN.active flag, correctly specify the btcd RPC host with its port (:18555), and set the rpclisten address to 127.0.0.1:10009 for improved clarity and security within the Docker environment.

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[gemini-code-assist]

Code Review

This pull request provides a welcome update to the Docker-based lnd payment guide. Key improvements include updating to the docker compose v2 syntax, removing an outdated section, and upgrading dependencies. The Dockerfiles are also enhanced with better version management and a health check.

However, I've identified a critical error in docker/lnd/start-lnd.sh. The script configures lnd to use the wrong port for the btcd RPC connection on simnet, which will prevent the setup from working as described. I've provided specific comments with suggestions to resolve this.

[gemini-code-assist]

The btcd RPC host is being configured with port 18555, which is the P2P port for simnet, not the RPC port. The correct RPC port for btcd on simnet is 18556. This configuration will prevent lnd from connecting to btcd and should be corrected.

Suggested change

	"--$BACKEND.rpchost"="$RPCHOST:18555" \
	"--$BACKEND.rpchost"="$RPCHOST:18556" \

[gemini-code-assist]

This comment incorrectly states that 18555 is the default btcd RPC port for simnet. The correct default RPC port for btcd on simnet is 18556. Port 18555 is the P2P port. This is misleading and should be corrected to avoid confusion, especially as the incorrect port is used later in this script.

Suggested change

	# [:18555] is the default btcd RPC port in SIMNET network.
	# [:18556] is the default btcd RPC port in SIMNET network.

[Liongrass]

Hi! Thank you for that PR!
My initial question is, is this guide for Signet or Simnet? Right now it makes references to both. Can you also double-check if the BTCD ports are correct?

[Euler-B]

Hi! Thank you for that PR! My initial question is, is this guide for Signet or Simnet? Right now it makes references to both. Can you also double-check if the BTCD ports are correct?

Hi! Thanks for the review. Sorry for the confusion; here are the details:

The guide is intended to use Simnet, as it's the fastest way to test the payment flows locally.

The Simnet ports are correct. Regarding Signet, I verified them while testing the faucet part, but I noticed a typo ("Segnet" instead of "Signet") which I've now fixed.

Regarding your question about the Dockerfile: I believe it's best to keep the Simnet focus to ensure the fastest onboarding for developers. I will refine the documentation to make this distinction clear and remove any ambiguous references to Signet where they aren't needed.

I've just updated the PR with these corrections. Let me know if you have any further suggestions!

[Euler-B]

@Liongrass I have completed the requested changes and the PR is ready for review. Thank you!"

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a great update to the Docker-based step-by-step guide for sending payments. Focusing on simnet and removing the obsolete faucet information makes the guide much more approachable and reliable for newcomers. The updates to use the modern docker compose syntax and improve the Docker configurations with version pinning, health checks, and more secure defaults are excellent enhancements. I have one minor suggestion to improve the clarity of the documentation.

[gemini-code-assist]

For better clarity and consistency, consider changing docker to docker compose. While docker compose is part of the docker CLI, the next sentence specifically mentions the docker-compose config file. Using docker compose explicitly would make it clearer to the user which tool is being referred to, especially since the rest of the document has been updated to use the docker compose syntax.

Suggested change

	the Lightning Network Daemon (`lnd`). This folder uses `docker` to
	package `lnd` and `btcd` together to make deploying the two daemons as easy as
	typing a few commands. All configuration between `lnd` and `btcd` are handled
	automatically by their `docker-compose` config file.
	the Lightning Network Daemon (`lnd`). This folder uses `docker compose` to
	package `lnd` and `btcd` together to make deploying the two daemons as easy as
	typing a few commands. All configuration between `lnd` and `btcd` are handled
	automatically by their `docker-compose` config file.

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a great update to the Docker-based step-by-step guide for sending payments. The focus on simnet, removal of obsolete information about the faucet, and updates to use modern Docker commands and practices significantly improve the guide's usability and reliability for new developers. The Dockerfile enhancements, such as version pinning, adding a health check, and improving security defaults, are also valuable contributions. I've found one minor inconsistency in the documentation that I've commented on. Overall, this is a solid improvement.

[Liongrass]

Hi Euler! Looks good so far, thank you for these changes. Next will be for me to try it out by following the guide strictly!

[Euler-B]

Hi Euler! Looks good so far, thank you for these changes. Next will be for me to try it out by following the guide strictly!

Perfect, thanks! Looking forward to your feedback. I'll be available to make any necessary adjustments based on your testing."

[lightninglabs-deploy]

@Euler-B, remember to re-request review from reviewers when ready

[Liongrass]

Thank you for this pull request and all the changes!

• Why not bump BTCD to 0.25.0 right away?
• You added a notice that LND needs to be installed. Does it, though? I think it should be enough for the user to clone the github repository and navigate to lnd/docker/
• If there should be a notice, than it's that docker should be installed. Maybe a link to the official installation guides could be helpful?
• Instead of instructing the user to add sudo to each command, why don't we tell them to run everything from the root shell? It would be enough to instruct them to switch to the root user with sudo -i
• I think we can remove the line # Check that segwit is active: and the one that follows it.

[Euler-B]

@Liongrass based on your feedback, I have implemented the following changes:

• Updated BTCD version to 0.25.0.

• Fixed comments to correctly guide the user to the lnd/docker directory.

• Added a Docker prerequisite warning, including a link to the official installation guide for multiple operating systems, since LND is cross-platform.

• Included the sudo -i directive, along with a warning advising users to exit this mode after completing the guide to avoid unintended system side effects.

• Removed SegWit activation check lines and updated the default wallet type to p2wkh, as it is the most optimized format for LND.

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a significant update to the Docker-based guide for sending payments with lnd. The changes focus on providing a seamless simnet experience, removing obsolete information like the non-functional faucet, and updating Docker configurations to follow modern best practices. The introduction of a HEALTHCHECK in the btcd Dockerfile and the update to docker compose syntax are great improvements. The guide is now much clearer and more reliable for new users. I have one suggestion in docker/README.md to improve the security recommendation regarding running Docker commands.

[gemini-code-assist]

Suggesting users switch to a root shell with sudo -i can be risky, especially for newcomers who might not be fully aware of the implications. It's generally better to promote safer practices.

A good alternative is to instruct users to run Docker commands with sudo if needed, or to follow Docker's official post-installation steps to manage Docker as a non-root user, which usually involves adding the user to the docker group.

Consider rephrasing this section to either show sudo in the commands or to link to Docker's documentation on non-root user setup.

For example:

> All commands should be executed from the `lnd/docker/` directory. Depending on your system's configuration, you may need to prefix `docker` commands with `sudo`. Alternatively, you can follow the [official Docker documentation](https://docs.docker.com/engine/install/linux-postinstall/) to allow running Docker commands without `sudo`.

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides an excellent update to the Docker-based getting-started guide. It modernizes the workflow by focusing on simnet, removing obsolete information, and updating dependencies and commands. The changes make the guide much more accurate and user-friendly for new developers. I've added a few minor suggestions to improve consistency in the documentation's formatting.

[gemini-code-assist]

The updated introduction removes backticks from terms like lnd, btcd, and docker-compose.yml. For consistency with the rest of the document, where such terms are enclosed in backticks for code formatting, it would be better to add them.

Suggested change

	This document is intended for those looking to get started with
	the Lightning Network Daemon (lnd). This folder uses docker to package lnd and
	btcd together, making the deployment of both daemons as simple as running a
	few commands. All configuration between lnd and btcd is handled automatically
	by the docker-compose.yml file
	This document is intended for those looking to get started with
	the Lightning Network Daemon (`lnd`). This folder uses `docker` to package `lnd` and
	`btcd` together, making the deployment of both daemons as simple as running a
	few commands. All configuration between `lnd` and `btcd` is handled automatically
	by the `docker-compose.yml` file

[gemini-code-assist]

For consistency, it's better to use backticks for command names like docker and sudo instead of bolding. Also, there's an extra space after Linux that should be removed, and sudo at the end of the sentence could also be in backticks for clarity.

Suggested change

>All commands should be executed from the `lnd/docker/` directory. Depending on your system's configuration, you may need to prefix **docker** commands with **sudo**. For `Linux` users, we highly recommend following the official [Docker documentation to manage Docker as a non-root](https://docs.docker.com/engine/install/linux-postinstall/) user, which allows you to run commands without sudo safely

>All commands should be executed from the `lnd/docker/` directory. Depending on your system's configuration, you may need to prefix `docker` commands with `sudo`. For `Linux` users, we highly recommend following the official [Docker documentation to manage Docker as a non-root](https://docs.docker.com/engine/install/linux-postinstall/) user, which allows you to run commands without `sudo` safely

[gemini-code-assist]

For consistency with the command used for the alice container earlier in the guide, docker exec -i -t should be changed to the more compact docker exec -it.

Suggested change

	$ docker exec -i -t bob bash
	$ docker exec -it bob bash

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a significant and valuable update to the Docker-based "Send Payment" guide. The changes modernize the documentation by focusing on simnet, removing obsolete sections like the offline faucet, and updating commands to the current docker compose syntax. The underlying Docker configuration is also improved with best practices such as version pinning for base images, adding health checks, and enhancing security by restricting RPC listening to localhost. The guide is now much clearer and more reliable for new developers. I have a couple of minor suggestions to further improve the polish of the documentation and Dockerfile.

[gemini-code-assist]

There's a minor typo with a double space after `Linux`. Removing it will improve the readability of this important note for users.

Suggested change

>All commands should be executed from the `lnd/docker/` directory. Depending on your system's configuration, you may need to prefix **docker** commands with **sudo**. For `Linux` users, we highly recommend following the official [Docker documentation to manage Docker as a non-root](https://docs.docker.com/engine/install/linux-postinstall/) user, which allows you to run commands without sudo safely

>All commands should be executed from the `lnd/docker/` directory. Depending on your system's configuration, you may need to prefix **docker** commands with **sudo**. For `Linux` users, we highly recommend following the official [Docker documentation to manage Docker as a non-root](https://docs.docker.com/engine/install/linux-postinstall/) user, which allows you to run commands without sudo safely

[gemini-code-assist]

There's a trailing space at the end of this line. While it doesn't break functionality for an ARG, it's good practice to remove it for code cleanliness.

ARG BTCD_VERSION=v0.25.0

[gemini-code-assist]

The removal of --$CHAIN.active and --rpclisten=$HOSTNAME:10009 are great improvements. The former is deprecated and the latter improves security by only listening on localhost within the container. However, the lnd command for the btcd backend is missing the --$CHAIN.active flag that is still present for the bitcoind backend. While this flag is deprecated, for consistency it might be better to remove it from the bitcoind block as well.

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a much-needed update to the Docker-based "Send Payment" guide. The changes significantly improve the user experience by focusing on a simnet environment, removing obsolete information about the offline faucet, and modernizing the Docker commands and configurations. The use of version pinning in Dockerfiles and the addition of a healthcheck are excellent improvements for reproducibility and robustness. Overall, this is a great contribution that makes the guide more accessible and reliable for new developers. I have one minor suggestion to improve clarity in one of the scripts.

[gemini-code-assist]

This comment about the btcd RPC port seems slightly misplaced. It's located within a section discussing lnd's RPC listener configuration (--rpclisten), which could be confusing as it refers to a different service and port. For better clarity, consider moving this comment closer to where the btcd backend is configured (e.g., near the --$BACKEND.rpchost flag) or removing it if it's deemed non-essential.

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a much-needed update to the Docker-based step-by-step guide for sending payments. The changes are excellent, focusing on simnet for a smoother developer experience, removing obsolete sections, and updating commands to the modern docker compose syntax. The underlying Docker configuration is also improved with updated dependencies, version pinning, a health check for btcd, and a fix for certificate generation. Overall, this makes the guide significantly more reliable and user-friendly. I've found a couple of minor areas for improvement to ensure consistency throughout the documentation and scripts.

[gemini-code-assist]

The --$CHAIN.active flag was removed for the btcd backend, but it's still present for the bitcoind backend. While lnd might default to activating the bitcoin chain, it's better to be explicit for clarity and consistency between the two backend configurations in this script.

Suggested change

	--noseedbackup \
	"--$CHAIN.active" \
	"--$CHAIN.$NETWORK" \
	--noseedbackup \
	"--$CHAIN.active" \
	"--$CHAIN.$NETWORK" \

[Euler-B]

/gemini review

[gemini-code-assist]

Code Review

This pull request provides a significant improvement to the Docker-based "send payment" guide. The changes, including focusing on simnet, removing obsolete information about the faucet, and modernizing Docker commands, make the guide much clearer and more reliable for new users. The updates to the Dockerfiles, such as version pinning, adding health checks, and improving configuration flexibility, are also excellent enhancements. The code is of high quality and the changes are well-executed. I have one suggestion to improve consistency in the documentation.

[Euler-B]

@Liongrass I've also added gemini-code-assist bot corrections to improve readability and security, especially for running commands on Linux. I think they really help make the guide more robust."

[Liongrass]

Hi Euler,
Thank you very much for these changes! Generally, it might be easier for both of us to not immediately act on the Gemini reviews and suggestions. I'm reading through them, but whether we adopt them should still be up to us.

I assume this line docker-compose up -d btcd should not have a dash? It should be docker compose?

Other than that, looks great now, thank you very much for your work!

[Euler-B]

Hi @Liongrass, My apologies for the unintentional use of the gemini-code-assist; I am new to open-source collaboration and I'm still learning the workflow. About the docker-compose command, you are correct that it goes without the hyphen. Thank you for pointing that out.

[Liongrass]

Super cool, thank you for these changes and your contribution to LND! I cannot promise you how fast this will get merged, as reviews can often take time, but it doesn't touch any of the core codebase either, so we can be optimistic!