功能介绍

借助该工具可以优化file，将Dockerfile的分层减少，从而达到使镜像变小的目的

该工具主要是分析RUN,ENV等指令，将能合并分层的指令进行自动化分层，比如：

RUN cd /path/to/dir

RUN yum install

两条指令可以合并为：

RUN cd /path/to/dir && yum install python

官方的实例

$ cat Dockerfile # 8 layers
FROM golang:1.10-alpine3.8 AS build
ENV DEP_VERSION 0.4.1
WORKDIR /go/src/github.com/orisano/gobase
RUN apk add --no-cache git make mailcap tzdata
RUN wget -O /usr/local/bin/dep https://github.com/golang/dep/releases/download/v${DEP_VERSION}/dep--amd64 && chmod +x /usr/local/bin/dep
RUN wget -O /usr/local/bin/depinst https://github.com/orisano/depinst/releases/download/1.0.1/depinst-linux-amd64 && chmod +x /usr/local/bin/depinst
COPY Gopkg.lock Gopkg.toml ./
RUN dep ensure -vendor-only
ENV CGO_ENABLED=0
ENV GO_LDFLAGS="-extldflags='-static'"
RUN go build -i ./vendor/...
COPY . .
RUN make build

$ minid # 6 layers
FROM golang:1.10-alpine3.8 AS build
ENV DEP_VERSION=0.4.1
WORKDIR /go/src/github.com/orisano/gobase
RUN apk add --no-cache git make mailcap tzdata && wget -O /usr/local/bin/dep https://github.com/golang/dep/releases/download/v${DEP_VERSION}/dep-linux-amd64 && chmod +x /usr/local/bin/dep && wget -O /usr/local/bin/depinst https://github.com/orisano/depinst/releases/download/1.0.1/depinst-linux-amd64 && chmod +x /usr/local/bin/depinst
COPY Gopkg.lock Gopkg.toml ./
RUN dep ensure -vendor-only
ENV CGO_ENABLED=0 GO_LDFLAGS="-extldflags='-static'"
RUN go build -i ./vendor/...
COPY . .
RUN make build

胜象大百科