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Does that Dockerfile build a container that only has that app in and it's required dependencies? Almost all of the ones I've seen given as examples seem to have

Does that Dockerfile build a container that only has that app in and it's required dependencies? Almost all of the ones I've seen given as examples seem to have an entire copy of the OS in.

jchw 8y ago
A container is basically a glorified chroot, so there is a few things not strictly needed, but I typically use Alpine as a base system, which has a shell, some core utils, and musl libc in just ~5 MB. Since it's on its own layer, it gets deduplicated both in build and at runtime with other Alpine containers (and many Dockerhub images have an Alpine option.) That being said, since Go binaries have no inherent dependencies, I have indeed made Docker images containing exactly one file: the Go binary. These containers are basically the same as fat binaries, with the benefits of Docker scheduling and networking at runtime.
- seabrookmx 8y ago
  > I have indeed made Docker images containing exactly one file To anyone reading this, you need some magic compiler flags in both Rust and GoLang to make sure it's a statically compiled binary (doesn't dynamically link against GNU lib-c). But yes, this is super neat. I also like how it reads in the docker file: FROM scratch ...
  - jchw 8y ago
    Ah yeah, without CGO_ENABLED=0, you'll get a very cryptic error when the ELF binfmt can't find the linker binary... Never tried it with Rust, but I look to using Rust in the future, so I guess I better find out what the flags are for Rust. Sidenote: It's often useful to have ca certs and timezone info. At that point it's probably not a bad idea to just use Alpine and apk add those things.
    - steveklabnik 8y ago
      By default, Rust compiles all Rust code statically, but the standard library depends on a libc. If you want to use MUSL, you can. If you bind to C libraries, you may need to configure it or not, it depends on how the wrapper is written.
      - seabrookmx 8y ago
        Thanks for the clarification! There was a recent HN article that did a step-by-step using rust+musl on Alpine. The "why" makes more sense now.

Does that Dockerfile build a container that only has that app in and it's required dependencies? Almost all of the ones I've seen given as examples seem to have an entire copy of the OS in.

jchw 8y ago

A container is basically a glorified chroot, so there is a few things not strictly needed, but I typically use Alpine as a base system, which has a shell, some core utils, and musl libc in just ~5 MB. Since it's on its own layer, it gets deduplicated both in build and at runtime with other Alpine containers (and many Dockerhub images have an Alpine option.) That being said, since Go binaries have no inherent dependencies, I have indeed made Docker images containing exactly one file: the Go binary. These containers are basically the same as fat binaries, with the benefits of Docker scheduling and networking at runtime.

seabrookmx 8y ago
> I have indeed made Docker images containing exactly one file To anyone reading this, you need some magic compiler flags in both Rust and GoLang to make sure it's a statically compiled binary (doesn't dynamically link against GNU lib-c). But yes, this is super neat. I also like how it reads in the docker file: FROM scratch ...
- jchw 8y ago
  Ah yeah, without CGO_ENABLED=0, you'll get a very cryptic error when the ELF binfmt can't find the linker binary... Never tried it with Rust, but I look to using Rust in the future, so I guess I better find out what the flags are for Rust. Sidenote: It's often useful to have ca certs and timezone info. At that point it's probably not a bad idea to just use Alpine and apk add those things.
  - steveklabnik 8y ago
    By default, Rust compiles all Rust code statically, but the standard library depends on a libc. If you want to use MUSL, you can. If you bind to C libraries, you may need to configure it or not, it depends on how the wrapper is written.
    - seabrookmx 8y ago
      Thanks for the clarification! There was a recent HN article that did a step-by-step using rust+musl on Alpine. The "why" makes more sense now.