Rust language itself is harsh. Your first contact with compiler and borrow checker uses to be traumatic until you realize they are actually to protect you against yourself. Once you understand that you begin to love that language.
But everything else apart of the language is kind, really comfortable I'd say. With cargo, compiling, testing, documenting, profiling and even publishing to crates.io (the Pypi of Rust) is a charm. Packaging is no exception of that as it is integrated with cargo assuming some configuration we're going to explain here.
To package my Rust applications into debian packages, I use cargo-deb. To install it just type:
dante@Camelot:~~/Projects/cifra-rust/$ cargo install cargo-deb
Updating crates.io index
Downloaded cargo-deb v1.32.0
Downloaded 1 crate (63.2 KB) in 0.36s
Installing cargo-deb v1.32.0
Downloaded crc v1.8.1
Downloaded build_const v0.2.2
[...]
Compiling crossbeam-deque v0.8.1
Compiling xz2 v0.1.6
Compiling toml v0.5.8
Compiling cargo_toml v0.10.1
Finished release [optimized] target(s) in 53.21s
Installing /home/dante/.cargo/bin/cargo-deb
Installed package `cargo-deb v1.32.0` (executable `cargo-deb`)
dante@Camelot:~$
Done that, you could start packaging simple applications. By default cargo deb obtains basic information from your Cargo.toml file. That way it loads next fields:
- name
- version
- license
- license-file
- description
- readme
- homepage
- repository
But seldom happens your application has no dependencies at all. To configure more advanced use cases, create a [package.metadata.deb] section in your Cargo.toml. In that section you can configure next fields:
- maintainer
- copyright
- changelog
- depends
- recommends
- enhances
- conflicts
- breaks
- replaces
- provides
- extended-description
- extended-description-file
- section
- priority
- assets
- maintainer-scripts
As a working example of this you can read this Cargo.toml version of my application Cifra.
There you can read general section from where cargo deb loads its basic information:
Cargo has a great documentation where you can find every section and tag explained.
Be aware that every file path you include in Cargo.toml is relative to Cargo.toml file.
Specific section for cargo-deb must not be long to have a working package:
Tags for this section are documented at cargo-deb homepage.
Section and priority tags are used to classify your application in Debian hierarchy. Although I've set them I think they are rather useless because official Debian repositories have higher requirement than cargo-deb can meet at the moment, so any debian package produced with cargo-deb will end in a personal repository were debian hierarchy for applications is not present.
Actually, most important tag is assets. That tag lets you set which files should be included in package and where they should be placed at installation. Format of that tag contents is straightforward. It is a list of tuples of three elements:
- Relative path to file to be included in package: That path is relative to Cargo.toml location.
- Absolute path to place that file in user computer.
- Permissions for that file at user computer.
I should have included a "depends" tag to add my package dependencies. Cifra depends on SQLite3 and that is not a Rust crate but a system package, so it is a dependency of Cifra debian package. If you want to use "depends" tag you must use debian dependency format, but actually is not necessary because cargo-deb can calculate your dependencies automatically if you don't use "depends" tag. It does it using ldd against your compiled artifact and searching with dpkg which system packages provides libraries detected by ldd.
Once you have your cargo-deb configuration in your Cargo.toml, building your debian package is as simple as:
dante@Camelot:~/Projects/cifra-rust/$ cargo deb
[...]
Finished release [optimized] target(s) in 0.17s
/home/dante/Projects/cifra-rust/target/debian/cifra_0.9.1_amd64.deb
dante@Camelot:~$
As you can see in the output, you will find your generated package in a new folder inside your project's called target/debian/.
Cargo deb is a wonderful tool which only downside is not being capable to meet Debian packaging policy to build packages suitable to be included in official repositories.
