![Zebra logotype](https://zfnd.org/wp-content/uploads/2022/03/zebra-logotype.png)

---

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## Contents

- [Contents](#contents)
- [About](#about)
  - [Using Zebra](#using-zebra)
- [Release Candidates](#release-candidates)
- [Getting Started](#getting-started)
  - [Building Zebra](#building-zebra)
    - [Optional Features](#optional-features)
  - [Configuring JSON-RPC for lightwalletd](#configuring-json-rpc-for-lightwalletd)
  - [System Requirements](#system-requirements)
    - [Memory Troubleshooting](#memory-troubleshooting)
    - [macOS Test Troubleshooting](#macos-test-troubleshooting)
  - [Network Ports and Data Usage](#network-ports-and-data-usage)
    - [Network Troubleshooting](#network-troubleshooting)
  - [Disk Usage](#disk-usage)
    - [Disk Troubleshooting](#disk-troubleshooting)
- [Known Issues](#known-issues)
- [Future Work](#future-work)
- [Documentation](#documentation)
- [Security](#security)
- [License](#license)

## About

[Zebra](https://zebra.zfnd.org/) is the Zcash Foundation's independent,
consensus-compatible implementation of a Zcash node, currently under
development. It can be used to join the Zcash peer-to-peer network, which helps
keeping Zcash working by validating and broadcasting transactions, and maintaining
the Zcash blockchain state in a distributed manner.

[Zcash](https://doc.zebra.zfnd.org/zebrad/index.html#about-zcash)
is a cryptocurrency designed to preserve the user's privacy.
If you just want to send and receive Zcash then you don't need to use Zebra
directly. You can download a Zcash wallet application which will handle that
for you.

Please [join us on Discord](https://discord.gg/na6QZNd) if you'd
like to find out more or get involved!

### Using Zebra

You would want to run Zebra if you want to contribute to the
Zcash network: the more nodes are run, the more reliable the network will be
in terms of speed and resistance to denial of service attacks, for example.

Zebra aims to be [faster, more secure, and more easily extensible](https://doc.zebra.zfnd.org/zebrad/index.html#zebra-advantages)
than other Zcash implementations.

## Release Candidates

Every few weeks, we release a [new Zebra version](https://github.com/ZcashFoundation/zebra/releases).

Zebra's network stack is interoperable with `zcashd`,
and Zebra implements all the features required to reach Zcash network consensus.
Currently, Zebra validates all of the Zcash consensus rules for the NU5 network upgrade.

Zebra validates blocks and transactions, but needs extra software to generate them:

- to generate transactions, [configure `zebrad`'s JSON-RPC port](https://github.com/ZcashFoundation/zebra#configuring-json-rpc-for-lightwalletd),
  and use a light wallet with `lightwalletd` and Zebra.
- to generate blocks, [compile `zebrad` with the `getblocktemplate-rpcs` feature](https://doc.zebra.zfnd.org/zebrad/#json-rpc), configure the JSON-RPC port,
  and use a mining pool or miner with Zebra's mining JSON-RPCs.
  Mining support is currently incomplete, experimental, and off by default.

## Getting Started

You can run Zebra using our Docker image.
This command will run our latest release, and sync it to the tip:

```sh
docker run zfnd/zebra:1.0.0-rc.6
```

For more information, read our [Docker documentation](book/src/user/docker.md).

### Building Zebra

Building Zebra requires [Rust](https://www.rust-lang.org/tools/install),
[libclang](https://clang.llvm.org/doxygen/group__CINDEX.html),
[pkg-config](http://pkgconf.org/), and a C++ compiler.

Zebra is tested with the latest `stable` Rust version. Earlier versions are not
supported or tested. Note that Zebra's code currently uses features introduced
in Rust 1.65, or any later stable release.

Below are quick summaries for installing the dependencies on your machine.

<details><summary><h4>General instructions for installing dependencies</h4></summary>

1. Install [`cargo` and `rustc`](https://www.rust-lang.org/tools/install).

2. Install Zebra's build dependencies:

   - **libclang** is a library that might have different names depending on your
     package manager. Typical names are `libclang`, `libclang-dev`, `llvm`, or
     `llvm-dev`.
   - **clang** or another C++ compiler: `g++` (all platforms) or `Xcode` (macOS).
   - **pkg-config**

</details>

<details><summary><h4>Dependencies on Arch</h4></summary>

```sh
sudo pacman -S rust clang pkgconf
```

Note that the package `clang` includes `libclang` as well as the C++ compiler.

</details>

Once the dependencies are in place, you can build Zebra

```sh
cargo install --locked --git https://github.com/ZcashFoundation/zebra --tag v1.0.0-rc.6 zebrad
```

You can start Zebra by

```sh
zebrad start
```

See the [Running Zebra](https://zebra.zfnd.org/user/run.html) section in the
book for more details.

#### Optional Features

You can also build Zebra with the following [Cargo features](https://doc.rust-lang.org/cargo/reference/features.html#command-line-feature-options):

- `sentry` for [Sentry monitoring](https://zebra.zfnd.org/user/requirements.html#sentry-production-monitoring);
- `filter-reload` for [dynamic tracing](https://zebra.zfnd.org/user/tracing.html#dynamic-tracing)
- `journald` for [`journald` logging](https://zebra.zfnd.org/user/tracing.html#journald-logging).
- `flamegraph` for [generating flamegraphs](https://zebra.zfnd.org/user/tracing.html#flamegraphs).
- `prometheus` for [Prometheus metrics](https://doc.zebra.zfnd.org/zebrad/#metrics).
- `getblocktemplate-rpcs` for [mining support](https://zebra.zfnd.org/user/mining.html).

You can arbitrarily combine the features by listing them as parameters of the `--features` flag:

```sh
cargo install --features="<feature1> <feature2> ..." ...
```

The features are also described in [the API
documentation](https://doc.zebra.zfnd.org/zebrad/index.html#zebra-feature-flags).
The debugging and monitoring features are disabled in release builds to increase
performance.

### Configuring JSON-RPC for lightwalletd

To use `zebrad` as a `lightwalletd` backend, give it this `~/.config/zebrad.toml`:

```toml
[rpc]
# listen for RPC queries on localhost
listen_addr = '127.0.0.1:8232'

# automatically use multiple CPU threads
parallel_cpu_threads = 0
```

**WARNING:** This config allows multiple Zebra instances to share the same RPC port.
See the [RPC config documentation](https://doc.zebra.zfnd.org/zebra_rpc/config/struct.Config.html) for details.

`lightwalletd` also requires a `zcash.conf` file.

It is recommended to use [adityapk00/lightwalletd](https://github.com/adityapk00/lightwalletd) because that is used in testing.
Other `lightwalletd` forks have limited support, see the [detailed `lightwalletd` instructions](https://github.com/ZcashFoundation/zebra/blob/main/book/src/user/lightwalletd.md#sync-lightwalletd).

### System Requirements

The recommended requirements for compiling and running `zebrad` are:

- 4 CPU cores
- 16 GB RAM
- 300 GB available disk space for building binaries and storing cached chain state
- 100 Mbps network connection, with 300 GB of uploads and downloads per month

We continuously test that our builds and tests pass on:

The _latest_ [GitHub Runners](https://docs.github.com/en/actions/using-github-hosted-runners/about-github-hosted-runners#supported-runners-and-hardware-resources) for:

- macOS
- Ubuntu

Docker:

- Debian Bullseye

Zebra's tests can take over an hour, depending on your machine.
We're working on making them faster.

`zebrad` might build and run fine on smaller and slower systems - we haven't
tested its exact limits yet.

For more detailed requirements, refer to the [documentation](https://zebra.zfnd.org/user/requirements.html).

#### Memory Troubleshooting

If Zebra's build runs out of RAM, try setting:
`export CARGO_BUILD_JOBS=2`

If Zebra's tests timeout or run out of RAM, try running:
`cargo test -- --test-threads=2`

(cargo uses all the processor cores on your machine by default.)

#### macOS Test Troubleshooting

Some of Zebra's tests deliberately cause errors that make Zebra panic.
macOS records these panics as crash reports.

If you are seeing "Crash Reporter" dialogs during Zebra tests,
you can disable them using this Terminal.app command:

```sh
defaults write com.apple.CrashReporter DialogType none
```

### Network Ports and Data Usage

Zebra uses the following inbound and outbound TCP ports:

- 8233 on Mainnet
- 18233 on Testnet

Outbound connections are required to sync, inbound connections are optional.
Zebra also needs access to the Zcash DNS seeders, via the OS DNS resolver (usually port 53).

Zebra needs some peers which have a round-trip latency of 2 seconds or less.
If this is a problem for you, please
[open a ticket.](https://github.com/ZcashFoundation/zebra/issues/new/choose)

`zebrad`'s typical mainnet network usage is:

- Initial sync: 100 GB download, we expect the initial download to grow to hundreds of gigabytes over time
- Ongoing updates: 10 MB - 10 GB upload and download per day, depending on user-created transaction size and peer requests

Zebra performs an initial sync every time its internal database version changes,
so some version upgrades might require a full download of the whole chain.

For more detailed information, refer to the [documentation](https://zebra.zfnd.org/user/run.html).

#### Network Troubleshooting

Some of Zebra's tests download Zcash blocks, so they might be unreliable depending on your network connection.
You can set `ZEBRA_SKIP_NETWORK_TESTS=1` to skip the network tests.

Zebra may be unreliable on Testnet, and under less-than-perfect network conditions.
See our [roadmap](#future-work) for details.

### Disk Usage

Zebra uses around 200 GB of space for cached mainnet data, and 10 GB of space for cached testnet data.
We expect disk usage to grow over time, so we recommend reserving at least 300 GB for mainnet nodes.

Zebra's database cleans up outdated data periodically, and when Zebra is shut down and restarted.

#### Disk Troubleshooting

Zebra's state commits changes using RocksDB database transactions.

If you forcibly terminate Zebra, or it panics,
any incomplete changes will be rolled back the next time it starts.

So Zebra's state should always be valid, unless your OS or disk hardware is corrupting data.

## Known Issues

There are a few bugs in Zebra that we're still working on fixing:

- If Zebra fails downloading the Zcash parameters, use [the Zcash parameters download script](https://github.com/zcash/zcash/blob/master/zcutil/fetch-params.sh) instead.

- Block download and verification sometimes times out during Zebra's initial sync [#5709](https://github.com/ZcashFoundation/zebra/issues/5709). The full sync still finishes reasonably quickly.

- No Windows support [#3801](https://github.com/ZcashFoundation/zebra/issues/3801). We used to test with Windows Server 2019, but not any more; see the issue for details.

- Experimental Tor support is disabled until [Zebra upgrades to the latest `arti-client`](https://github.com/ZcashFoundation/zebra/issues/5492). This happened due to a Rust dependency conflict, which could only be resolved by `arti` upgrading to a version of `x25519-dalek` with the dependency fix.

- Orchard proofs [fail to verify when Zebra is compiled with Rust 1.69 (nightly Rust)](https://github.com/zcash/halo2/issues/737). This will be resolved in the next Orchard release after 0.3.0.

- Output of `help`, `--help` flag, and usage of invalid commands or options are inconsistent [#5502](https://github.com/ZcashFoundation/zebra/issues/5502). See the issue for details.

## Future Work

Performance and Reliability:

- Reliable syncing under poor network conditions
- Additional batch verification
- Performance tuning

Currently, the following features are out of scope:

- Optional Zcash network protocol messages
- Consensus rules removed before Canopy activation (Zebra checkpoints on Canopy activation)

## Documentation

The [Zebra website](https://zebra.zfnd.org/) contains user documentation, such
as how to run or configure Zebra, set up metrics integrations, etc., as well as
developer documentation, such as design documents. We also render [API
documentation](https://doc.zebra.zfnd.org) for the external API of our crates,
as well as [internal documentation](https://doc-internal.zebra.zfnd.org) for
private APIs.

## Security

Zebra has a [responsible disclosure policy](https://github.com/ZcashFoundation/zebra/blob/main/SECURITY.md), which we encourage security researchers to follow.

## License

Zebra is distributed under the terms of both the MIT license
and the Apache License (Version 2.0).

See [LICENSE-APACHE](LICENSE-APACHE) and [LICENSE-MIT](LICENSE-MIT).
