# How To: Build Tectonic: Install Dependencies With cargo-vcpkg
A convenient, fairly cross-platform way to install Tectonic’s dependencies is
using the [cargo-vcpkg] tool. It will take care of setting up [vcpkg], providing
the needed dependencies, and informing Tectonic’s build system about how to find
them. It will, however, generally require that the dependencies be compiled from
scratch.
[cargo-vcpkg]: https://crates.io/crates/cargo-vcpkg
[vcpkg]: https://vcpkg.readthedocs.io/
First, install [cargo-vcpkg] if needed:
```sh
cargo install cargo-vcpkg
```
Then, in the Tectonic source tree, run the command to obtain all of the needed
dependencies:
```sh
cargo vcpkg build
```
Then set the `VCPKG_ROOT` environment variable to tell the build system where
the dependencies may be found. In a [bash] shell, a good command is:
```sh
export VCPKG_ROOT="${CARGO_TARGET_DIR:-$(pwd)/target}/vcpkg"
```
[bash]: https://www.gnu.org/software/bash/
If you’re building on Windows, you’ll likely want to make sure that your
[`RUSTFLAGS`] variable includes a `+crt-static` [target feature] to get the
[vcpkg] build scripts to use the `x64-windows-static` [vcpkg triplet], which is
the default one used by our [cargo-vcpkg] setup, as opposed to
`x64-windows-static-md`, which is activated otherwise. And if you’ve done the
full vcpkg install, you might as well build with [an external Harfbuzz][external-harfbuzz].
Therefore a full Windows build invocation — launched from bash — might look like
this:
[`RUSTFLAGS`]: https://doc.rust-lang.org/cargo/reference/environment-variables.html
[target feature]: https://rust-lang.github.io/packed_simd/perf-guide/target-feature/rustflags.html
[vcpkg triplet]: https://vcpkg.readthedocs.io/en/latest/users/triplets/
[external-harfbuzz]: ./index.md#choose-cargo-features
```sh
cargo vcpkg build
export VCPKG_ROOT="${CARGO_TARGET_DIR:-$(pwd)/target}/vcpkg"
export RUSTFLAGS='-Ctarget-feature=+crt-static' # Windows only
export TECTONIC_DEP_BACKEND=vcpkg
cargo build --features external-harfbuzz
```
Note that if you are going to run additional commands such as `cargo test`,
you’re going to need to ensure that the same environment variables *and feature
flags* are used consistently.