I haven't seen ubuntu's version of distroless but the general term implies a container image with an empty shell of what a linux distro provides. Leaving behind only the minimum files for running your app rather than all the cruft around running and maintaining a distro, which is normally all done at container build time.

From the Debian based https://github.com/GoogleContainerTools/distroless/blob/main...

Statically compiled applications (Go) that do not require libc can use the gcr.io/distroless/static image, which contains:

    - ca-certificates
    - A /etc/passwd entry for a root user
    - A /tmp directory
    - tzdata

Applications that require libc but do not need libssl can use the gcr.io/distroless/base-nossl, which contains all of the packages in gcr.io/distroless/static, and

    - glibc

Most other applications (and Go apps that require libc/cgo) should start with gcr.io/distroless/base, which contains all of the packages in gcr.io/distroless/static, and

    - glibc
    - libssl