Docker inside Docker 基于 Alpine Linux

https://hub.docker.com/_/docker/

docker run -it --privileged --name dind -d docker:dind

[root@CentOS75 ~]# docker exec -it some-docker sh
/ # docker version
Client:
 Version:      18.05.0-ce
 API version:  1.37
 Go version:   go1.9.2
 Git commit:   f150324
 Built:        Wed May  9 22:11:29 2018
 OS/Arch:      linux/amd64
 Experimental: false
 Orchestrator: swarm

Server:
 Engine:
  Version:      18.05.0-ce
  API version:  1.37 (minimum version 1.12)
  Go version:   go1.10.1
  Git commit:   f150324
  Built:        Wed May  9 22:20:42 2018
  OS/Arch:      linux/amd64
  Experimental: false
/ # 

vi /etc/os-release 

NAME="Alpine Linux"
ID=alpine
VERSION_ID=3.7.0
PRETTY_NAME="Alpine Linux v3.7"
HOME_URL="http://alpinelinux.org"
BUG_REPORT_URL="http://bugs.alpinelinux.org"

https://github.com/docker-library/docker/blob/9ecb1c3a6bd766b69eb1858ef721f62fbd930a2b/18.06-rc/dind/Dockerfile

FROM docker:18.06-rc

# https://github.com/docker/docker/blob/master/project/PACKAGERS.md#runtime-dependencies
RUN set -eux;     apk add --no-cache         btrfs-progs         e2fsprogs         e2fsprogs-extra         iptables         xfsprogs         xz # pigz: https://github.com/moby/moby/pull/35697 (faster gzip implementation)
        pigz     ; # only install zfs if it‘s available for the current architecture
# https://git.alpinelinux.org/cgit/aports/tree/main/zfs/APKBUILD?h=3.6-stable#n9 ("all !armhf !ppc64le" as of 2017-11-01)
# "apk info XYZ" exits with a zero exit code but no output when the package exists but not for this arch
    if zfs="$(apk info --no-cache --quiet zfs)" && [ -n "$zfs" ]; then         apk add --no-cache zfs;     fi

# TODO aufs-tools

# set up subuid/subgid so that "--userns-remap=default" works out-of-the-box
RUN set -x     && addgroup -S dockremap     && adduser -S -G dockremap dockremap     && echo ‘dockremap:165536:65536‘ >> /etc/subuid     && echo ‘dockremap:165536:65536‘ >> /etc/subgid

# https://github.com/docker/docker/tree/master/hack/dind
ENV DIND_COMMIT 52379fa76dee07ca038624d639d9e14f4fb719ff

RUN set -ex;     apk add --no-cache --virtual .fetch-deps libressl;     wget -O /usr/local/bin/dind "https://raw.githubusercontent.com/docker/docker/${DIND_COMMIT}/hack/dind";     chmod +x /usr/local/bin/dind;     apk del .fetch-deps

COPY dockerd-entrypoint.sh /usr/local/bin/

VOLUME /var/lib/docker
EXPOSE 2375

ENTRYPOINT ["dockerd-entrypoint.sh"]
CMD []

FROM alpine:3.7

RUN apk add --no-cache         ca-certificates

# set up nsswitch.conf for Go‘s "netgo" implementation (which Docker explicitly uses)
# - https://github.com/docker/docker-ce/blob/v17.09.0-ce/components/engine/hack/make.sh#L149
# - https://github.com/golang/go/blob/go1.9.1/src/net/conf.go#L194-L275
# - docker run --rm debian:stretch grep ‘^hosts:‘ /etc/nsswitch.conf
RUN [ ! -e /etc/nsswitch.conf ] && echo ‘hosts: files dns‘ > /etc/nsswitch.conf

ENV DOCKER_CHANNEL test
ENV DOCKER_VERSION 18.06.0-ce-rc3
# TODO ENV DOCKER_SHA256
# https://github.com/docker/docker-ce/blob/5b073ee2cf564edee5adca05eee574142f7627bb/components/packaging/static/hash_files !!
# (no SHA file artifacts on download.docker.com yet as of 2017-06-07 though)

RUN set -ex; # why we use "curl" instead of "wget":
# + wget -O docker.tgz https://download.docker.com/linux/static/stable/x86_64/docker-17.03.1-ce.tgz
# Connecting to download.docker.com (54.230.87.253:443)
# wget: error getting response: Connection reset by peer
    apk add --no-cache --virtual .fetch-deps         curl         tar     ;     # this "case" statement is generated via "update.sh"
    apkArch="$(apk --print-arch)";     case "$apkArch" in         x86_64) dockerArch=‘x86_64‘ ;;         armhf) dockerArch=‘armel‘ ;;         aarch64) dockerArch=‘aarch64‘ ;;         ppc64le) dockerArch=‘ppc64le‘ ;;         s390x) dockerArch=‘s390x‘ ;;         *) echo >&2 "error: unsupported architecture ($apkArch)"; exit 1 ;;    esac;         if ! curl -fL -o docker.tgz "https://download.docker.com/linux/static/${DOCKER_CHANNEL}/${dockerArch}/docker-${DOCKER_VERSION}.tgz"; then         echo >&2 "error: failed to download ‘docker-${DOCKER_VERSION}‘ from ‘${DOCKER_CHANNEL}‘ for ‘${dockerArch}‘";         exit 1;     fi;         tar --extract         --file docker.tgz         --strip-components 1         --directory /usr/local/bin/     ;     rm docker.tgz;         apk del .fetch-deps;         dockerd -v;     docker -v

COPY modprobe.sh /usr/local/bin/modprobe
COPY docker-entrypoint.sh /usr/local/bin/

ENTRYPOINT ["docker-entrypoint.sh"]
CMD ["sh"]