如果你改docker的源码，那就必然需要自己从源码去编译docker，本文介绍如何从源码编译docker。

编译docker的过程很复杂，但是庆幸的是docker官方已经将这个复杂的过程简单化了，它提供了一个Makefile和Dockerfile，将复杂的操作都封装起来了，对于我们可以不去太关注里面的细节。本文主要介绍一下编译流程以及对于中国用户来说如何解决一些源下载慢甚至下载不了的问题。

  1. 硬件环境。编译docker的过程是挺耗费内存的，如果你使用虚拟机的话，建议至少分2GB的内存。我这里使用的OS是Ubuntu 14.04，硬件是8核16GB的服务器。

  2. 安装docker。因为docker是在容器里面去编译的，所以我们需要先安装docker（如果下面的命令安装失败，请参考我之前的文章《Ubuntu安装Docker》）。

    apt-get install linux-image-extra-$(uname -r) linux-image-extra-virtual
curl -sSL https://get.daocloud.io/docker | sh

  3. 下载源码。

    git clone https://github.com/docker/docker.git
cd docker

  4. 构建编译docker的环境。docker的编译是在容器中进行的，构建这个容器的命令很简单，在docker目录执行make build即可。我们看Makefile文件可以发现，执行make build的时候其实值执行了如下命令：

    docker build ${BUILD_APT_MIRROR} ${DOCKER_BUILD_ARGS} -t "$(DOCKER_IMAGE)" -f "$(DOCKERFILE)" .`

    其实默认就是用Makefile同级目录下的Dockerfile构建出一个编译docker的镜像，这个镜像具备了编译docker的所有东西。内容如下：

    # This file describes the standard way to build Docker, using docker
# Usage:
#
# # Assemble the full dev environment. This is slow the first time.
# docker build -t docker .
#
# # Mount your source in an interactive container for quick testing:
# docker run -v `pwd`:/go/src/github.com/docker/docker --privileged -i -t docker bash
#
# # Run the test suite:
# docker run --privileged docker hack/make.sh test-unit test-integration-cli test-docker-py
#
# # Publish a release:
# docker run --privileged \
#  -e AWS_S3_BUCKET=baz \
#  -e AWS_ACCESS_KEY=foo \
#  -e AWS_SECRET_KEY=bar \
#  -e GPG_PASSPHRASE=gloubiboulga \
#  docker hack/release.sh
#
# Note: AppArmor used to mess with privileged mode, but this is no longer
# the case. Therefore, you don't have to disable it anymore.
#

FROM debian:jessie

# allow replacing httpredir or deb mirror
ARG APT_MIRROR=deb.debian.org
RUN sed -ri "s/(httpredir|deb).debian.org/$APT_MIRROR/g" /etc/apt/sources.list

# Add zfs ppa
COPY keys/launchpad-ppa-zfs.asc /go/src/github.com/docker/docker/keys/
RUN apt-key add /go/src/github.com/docker/docker/keys/launchpad-ppa-zfs.asc
RUN echo deb http://ppa.launchpad.net/zfs-native/stable/ubuntu trusty main > /etc/apt/sources.list.d/zfs.list

# Packaged dependencies
RUN apt-get update && apt-get install -y \
    apparmor \
    apt-utils \
    aufs-tools \
    automake \
    bash-completion \
    binutils-mingw-w64 \
    bsdmainutils \
    btrfs-tools \
    build-essential \
    clang \
    cmake \
    createrepo \
    curl \
    dpkg-sig \
    gcc-mingw-w64 \
    git \
    iptables \
    jq \
    less \
    libapparmor-dev \
    libcap-dev \
    libltdl-dev \
    libnl-3-dev \
    libprotobuf-c0-dev \
    libprotobuf-dev \
    libsqlite3-dev \
    libsystemd-journal-dev \
    libtool \
    libzfs-dev \
    mercurial \
    net-tools \
    pkg-config \
    protobuf-compiler \
    protobuf-c-compiler \
    python-dev \
    python-mock \
    python-pip \
    python-websocket \
    tar \
    ubuntu-zfs \
    vim \
    vim-common \
    xfsprogs \
    zip \
    --no-install-recommends \
    && pip install awscli==1.10.15
# Get lvm2 source for compiling statically
ENV LVM2_VERSION 2.02.103
RUN mkdir -p /usr/local/lvm2 \
    && curl -fsSL "https://mirrors.kernel.org/sourceware/lvm2/LVM2.${LVM2_VERSION}.tgz" \
        | tar -xzC /usr/local/lvm2 --strip-components=1
# See https://git.fedorahosted.org/cgit/lvm2.git/refs/tags for release tags

# Compile and install lvm2
RUN cd /usr/local/lvm2 \
    && ./configure \
        --build="$(gcc -print-multiarch)" \
        --enable-static_link \
    && make device-mapper \
    && make install_device-mapper
# See https://git.fedorahosted.org/cgit/lvm2.git/tree/INSTALL

# Configure the container for OSX cross compilation
ENV OSX_SDK MacOSX10.11.sdk
ENV OSX_CROSS_COMMIT a9317c18a3a457ca0a657f08cc4d0d43c6cf8953
RUN set -x \
    && export OSXCROSS_PATH="/osxcross" \
    && git clone https://github.com/tpoechtrager/osxcross.git $OSXCROSS_PATH \
    && ( cd $OSXCROSS_PATH && git checkout -q $OSX_CROSS_COMMIT) \
    && curl -sSL https://s3.dockerproject.org/darwin/v2/${OSX_SDK}.tar.xz -o "${OSXCROSS_PATH}/tarballs/${OSX_SDK}.tar.xz" \
    && UNATTENDED=yes OSX_VERSION_MIN=10.6 ${OSXCROSS_PATH}/build.sh
ENV PATH /osxcross/target/bin:$PATH

# Install seccomp: the version shipped in trusty is too old
ENV SECCOMP_VERSION 2.3.1
RUN set -x \
    && export SECCOMP_PATH="$(mktemp -d)" \
    && curl -fsSL "https://github.com/seccomp/libseccomp/releases/download/v${SECCOMP_VERSION}/libseccomp-${SECCOMP_VERSION}.tar.gz" \
        | tar -xzC "$SECCOMP_PATH" --strip-components=1 \
    && ( \
        cd "$SECCOMP_PATH" \
        && ./configure --prefix=/usr/local \
        && make \
        && make install \
        && ldconfig \
    ) \
    && rm -rf "$SECCOMP_PATH"

# Install Go
# IMPORTANT: If the version of Go is updated, the Windows to Linux CI machines
#            will need updating, to avoid errors. Ping #docker-maintainers on IRC
#            with a heads-up.
ENV GO_VERSION 1.7.4
RUN curl -fsSL "https://golang.org/dl/go${GO_VERSION}.linux-amd64.tar.gz" \
    | tar -xzC /usr/local

ENV PATH /go/bin:/usr/local/go/bin:$PATH
ENV GOPATH /go

# Compile Go for cross compilation
ENV DOCKER_CROSSPLATFORMS \
    linux/386 linux/arm \
    darwin/amd64 \
    freebsd/amd64 freebsd/386 freebsd/arm \
    windows/amd64 windows/386 \
    solaris/amd64

# Dependency for golint
ENV GO_TOOLS_COMMIT 823804e1ae08dbb14eb807afc7db9993bc9e3cc3
RUN git clone https://github.com/golang/tools.git /go/src/golang.org/x/tools \
    && (cd /go/src/golang.org/x/tools && git checkout -q $GO_TOOLS_COMMIT)

# Grab Go's lint tool
ENV GO_LINT_COMMIT 32a87160691b3c96046c0c678fe57c5bef761456
RUN git clone https://github.com/golang/lint.git /go/src/github.com/golang/lint \
    && (cd /go/src/github.com/golang/lint && git checkout -q $GO_LINT_COMMIT) \
    && go install -v github.com/golang/lint/golint

# Install CRIU for checkpoint/restore support
ENV CRIU_VERSION 2.9
RUN mkdir -p /usr/src/criu \
    && curl -sSL https://github.com/xemul/criu/archive/v${CRIU_VERSION}.tar.gz | tar -v -C /usr/src/criu/ -xz --strip-components=1 \
    && cd /usr/src/criu \
    && make \
    && make install-criu

# Install two versions of the registry. The first is an older version that
# only supports schema1 manifests. The second is a newer version that supports
# both. This allows integration-cli tests to cover push/pull with both schema1
# and schema2 manifests.
ENV REGISTRY_COMMIT_SCHEMA1 ec87e9b6971d831f0eff752ddb54fb64693e51cd
ENV REGISTRY_COMMIT 47a064d4195a9b56133891bbb13620c3ac83a827
RUN set -x \
    && export GOPATH="$(mktemp -d)" \
    && git clone https://github.com/docker/distribution.git "$GOPATH/src/github.com/docker/distribution" \
    && (cd "$GOPATH/src/github.com/docker/distribution" && git checkout -q "$REGISTRY_COMMIT") \
    && GOPATH="$GOPATH/src/github.com/docker/distribution/Godeps/_workspace:$GOPATH" \
        go build -o /usr/local/bin/registry-v2 github.com/docker/distribution/cmd/registry \
    && (cd "$GOPATH/src/github.com/docker/distribution" && git checkout -q "$REGISTRY_COMMIT_SCHEMA1") \
    && GOPATH="$GOPATH/src/github.com/docker/distribution/Godeps/_workspace:$GOPATH" \
        go build -o /usr/local/bin/registry-v2-schema1 github.com/docker/distribution/cmd/registry \
    && rm -rf "$GOPATH"

# Install notary and notary-server
ENV NOTARY_VERSION v0.5.0
RUN set -x \
    && export GOPATH="$(mktemp -d)" \
    && git clone https://github.com/docker/notary.git "$GOPATH/src/github.com/docker/notary" \
    && (cd "$GOPATH/src/github.com/docker/notary" && git checkout -q "$NOTARY_VERSION") \
    && GOPATH="$GOPATH/src/github.com/docker/notary/vendor:$GOPATH" \
        go build -o /usr/local/bin/notary-server github.com/docker/notary/cmd/notary-server \
    && GOPATH="$GOPATH/src/github.com/docker/notary/vendor:$GOPATH" \
        go build -o /usr/local/bin/notary github.com/docker/notary/cmd/notary \
    && rm -rf "$GOPATH"

# Get the "docker-py" source so we can run their integration tests
ENV DOCKER_PY_COMMIT e2655f658408f9ad1f62abdef3eb6ed43c0cf324
RUN git clone https://github.com/docker/docker-py.git /docker-py \
    && cd /docker-py \
    && git checkout -q $DOCKER_PY_COMMIT \
    && pip install -r test-requirements.txt

# Install yamllint for validating swagger.yaml
RUN pip install yamllint==1.5.0

# Install go-swagger for validating swagger.yaml
ENV GO_SWAGGER_COMMIT c28258affb0b6251755d92489ef685af8d4ff3eb
RUN git clone https://github.com/go-swagger/go-swagger.git /go/src/github.com/go-swagger/go-swagger \
    && (cd /go/src/github.com/go-swagger/go-swagger && git checkout -q $GO_SWAGGER_COMMIT) \
    && go install -v github.com/go-swagger/go-swagger/cmd/swagger

# Set user.email so crosbymichael's in-container merge commits go smoothly
RUN git config --global user.email 'docker-dummy@example.com'

# Add an unprivileged user to be used for tests which need it
RUN groupadd -r docker
RUN useradd --create-home --gid docker unprivilegeduser

VOLUME /var/lib/docker
WORKDIR /go/src/github.com/docker/docker
ENV DOCKER_BUILDTAGS apparmor pkcs11 seccomp selinux

# Let us use a .bashrc file
RUN ln -sfv $PWD/.bashrc ~/.bashrc
# Add integration helps to bashrc
RUN echo "source $PWD/hack/make/.integration-test-helpers" >> /etc/bash.bashrc

# Register Docker's bash completion.
RUN ln -sv $PWD/contrib/completion/bash/docker /etc/bash_completion.d/docker

# Get useful and necessary Hub images so we can "docker load" locally instead of pulling
COPY contrib/download-frozen-image-v2.sh /go/src/github.com/docker/docker/contrib/
RUN ./contrib/download-frozen-image-v2.sh /docker-frozen-images \
    buildpack-deps:jessie@sha256:25785f89240fbcdd8a74bdaf30dd5599a9523882c6dfc567f2e9ef7cf6f79db6 \
    busybox:latest@sha256:e4f93f6ed15a0cdd342f5aae387886fba0ab98af0a102da6276eaf24d6e6ade0 \
    debian:jessie@sha256:f968f10b4b523737e253a97eac59b0d1420b5c19b69928d35801a6373ffe330e \
    hello-world:latest@sha256:8be990ef2aeb16dbcb9271ddfe2610fa6658d13f6dfb8bc72074cc1ca36966a7
# See also "hack/make/.ensure-frozen-images" (which needs to be updated any time this list is)

# Install tomlv, vndr, runc, containerd, tini, docker-proxy
# Please edit hack/dockerfile/install-binaries.sh to update them.
COPY hack/dockerfile/binaries-commits /tmp/binaries-commits
COPY hack/dockerfile/install-binaries.sh /tmp/install-binaries.sh
RUN /tmp/install-binaries.sh tomlv vndr runc containerd tini proxy bindata

# Wrap all commands in the "docker-in-docker" script to allow nested containers
ENTRYPOINT ["hack/dind"]

# Upload docker source
COPY . /go/src/github.com/docker/docker

    对于中国用户来说，如果没有科学上网工具，直接使用这个Dockerfile，基本上不会成功，因为有些下载不了。所以我们需要修改几个地方，特别是装软件的地方，需要下载很多东西。我的修改点如下：

    • 修改替换Debian源为中国的源（大约第30行）

      # 修改前
ARG APT_MIRROR=deb.debian.org

# 修改后
ARG APT_MIRROR=ftp.cn.debian.org

    • 修改pip源为国内的源（大约第85行）

      # 修改前
&& pip install awscli==1.10.15

# 修改后
&& pip install awscli==1.10.15 -i http://mirrors.aliyun.com/pypi/simple

    • 修改下载go安装包的地址（大约133行）。这里需要注意GO_VERSION的版本，不同版本的地址可以去http://golangtc.com/download获取。

      # 修改前
ENV GO_VERSION 1.7.4
RUN curl -fsSL "https://golang.org/dl/go${GO_VERSION}.linux-amd64.tar.gz" \
 | tar -xzC /usr/local

# 修改后
ENV GO_VERSION 1.7.4
RUN curl -fsSL "http://golangtc.com/static/go/1.7.4/go1.7.4.linux-amd64.tar.gz" \
 | tar -xzC /usr/local

    其他的基本都是从docker hub和github下载东西，对于docker hub可以配置加速器，github没有被墙，但可能不稳定或者速度比较慢。整个容器的过程还是比较慢的，不过比起编译Linux内核和Gcc还是快了不少的。如果不出什么错的话，编译完之后我们就会有一个叫docker-dev的容器，我编译出来有2.439GB。这样我们就有编译docker源码的环境了。

  5. 编译docker。这个也很简单，在刚才的目录执行make binary即可。如果没出什么错，我们可以看到如下信息：

    ---> Making bundle: binary (in bundles/1.14.0-dev/binary)
Building: bundles/1.14.0-dev/binary-client/docker-1.14.0-dev
Created binary: bundles/1.14.0-dev/binary-client/docker-1.14.0-dev
Building: bundles/1.14.0-dev/binary-daemon/dockerd-1.14.0-dev
Created binary: bundles/1.14.0-dev/binary-daemon/dockerd-1.14.0-dev
Copying nested executables into bundles/1.14.0-dev/binary-daemon

    可以看到编译出来的东西在bundles/1.14.0-dev/binary目录，有client(bundles/1.14.0-dev/binary-client/docker)和daemon(bundles/1.14.0-dev/binary-daemon/dockerd)：

至此编译结束了。