docker - Ubuntu14.04和Ubuntu12.04 Docker镜像

Question

我有一些基于ubuntu12.04镜像的docker镜像。我想将其中一些迁移到基于ubuntu14.04的版本。但是ubuntu14.04镜像比ubuntu12.04镜像大了近120 MB。

谁知道为什么以及如何减少ubuntu14.04图片

运行docker images

myregistry/ubuntu          14.04    xxx   xxx        225.4 MB
myregistry/ubuntu          12.04    xxx   xxx        103.9 MB

Answer 1

我看到的第一个问题是您还没有向我们展示如何获得所拥有的图像。它们来自非根注册表(“myregistry”)，并且您已经在复制/粘贴练习中省略了哈希。

当我下载这些图像时，会看到以下内容:

WineSoaked$ docker pull ubuntu:12.04
Pulling repository ubuntu
b45a6cbea6d1: Download complete
511136ea3c5a: Download complete
0b825e3a3d82: Download complete
3327dfd9dc7d: Download complete
4e284c9e0a9e: Download complete
ae9570f7a92a: Download complete
acc75c8f0e1d: Download complete

WineSoaked$ docker pull ubuntu:14.04
Pulling repository ubuntu
6b4e8a7373fe: Download complete
511136ea3c5a: Download complete
b18d0a2076a1: Download complete
67b66f26d423: Download complete
25c4824a5268: Download complete
8b1c48305638: Download complete
c900195dcbf3: Download complete

WineSoaked$ docker images
REPOSITORY      TAG             IMAGE ID        CREATED         VIRTUAL SIZE
ubuntu          14.04           6b4e8a7373fe    6 days ago      194.9 MB
ubuntu          12.04           b45a6cbea6d1    6 days ago      112.3 MB

您会注意到，每个拉取中的第二个哈希都是相同的。这就是这些构建的基础图像。其余部分与用于构建它们的dockerfile有关。我们去看看吧？

这是12.04的 Dockerfile:

FROM scratch
ADD precise-core-amd64.tar.gz /

# a few minor docker-specific tweaks
# see https://github.com/dotcloud/docker/blob/master/contrib/mkimage/debootstrap
RUN echo '#!/bin/sh' > /usr/sbin/policy-rc.d \
    && echo 'exit 101' >> /usr/sbin/policy-rc.d \
    && chmod +x /usr/sbin/policy-rc.d \
    \
    && dpkg-divert --local --rename --add /sbin/initctl \
    && cp -a /usr/sbin/policy-rc.d /sbin/initctl \
    && sed -i 's/^exit.*/exit 0/' /sbin/initctl \
    \
    && echo 'force-unsafe-io' > /etc/dpkg/dpkg.cfg.d/docker-apt-speedup \
    \
    && echo 'DPkg::Post-Invoke { "rm -f /var/cache/apt/archives/*.deb    /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true"; };' > /etc/apt/apt.conf.d/docker-clean \
    && echo 'APT::Update::Post-Invoke { "rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true"; };' >> /etc/apt/apt.conf.d/docker-clean \
    && echo 'Dir::Cache::pkgcache ""; Dir::Cache::srcpkgcache "";' >> /etc/apt/apt.conf.d/docker-clean \
    \
    && echo 'Acquire::Languages "none";' > /etc/apt/apt.conf.d/docker-no-languages \
    \
    && echo 'Acquire::GzipIndexes "true"; Acquire::CompressionTypes::Order:: "gz";' > /etc/apt/apt.conf.d/docker-gzip-indexes

# delete all the apt list files since they're big and get stale quickly
RUN rm -rf /var/lib/apt/lists/*
# this forces "apt-get update" in dependent images, which is also good

# enable the universe
RUN sed -i 's/^#\s*\(deb.*universe\)$/\1/g' /etc/apt/sources.list

# upgrade packages for now, since the tarballs aren't updated frequently enough
RUN apt-get update && apt-get dist-upgrade -y && rm -rf /var/lib/apt/lists/*

# overwrite this with 'CMD []' in a dependent Dockerfile
CMD ["/bin/bash"]

Dockerfile中的每个命令都对应于一个哈希，哈希是构成AUFS文件系统的中间镜像。以机智:

511136ea3c5a对应于FROM scratch

0b825e3a3d82对应于ADD precise-core-amd64.tar.gz ...

3327dfd9dc7d与史诗般的RUN一起

4e284c9e0a9e与RUN rm -rf /var/lib/apt/lists/*一起

ae9570f7a92a与RUN sed -i 's/^#\s*\(deb.*universe\)$/\1/g' /etc/apt/sources.list一起

acc75c8f0e1d和RUN apt-get update && apt-get dist-upgrade -y && rm -rf /var/lib/apt/lists/*一起使用
b45a6cbea6d1对应于生成的图像。

您也可以根据其 Dockerfile分解14.04图像:

FROM scratch
ADD trusty-core-amd64.tar.gz /

# a few minor docker-specific tweaks
# see https://github.com/dotcloud/docker/blob/master/contrib/mkimage/debootstrap
RUN echo '#!/bin/sh' > /usr/sbin/policy-rc.d \
    && echo 'exit 101' >> /usr/sbin/policy-rc.d \
    && chmod +x /usr/sbin/policy-rc.d \
    \
    && dpkg-divert --local --rename --add /sbin/initctl \
    && cp -a /usr/sbin/policy-rc.d /sbin/initctl \
    && sed -i 's/^exit.*/exit 0/' /sbin/initctl \
    \
    && echo 'force-unsafe-io' > /etc/dpkg/dpkg.cfg.d/docker-apt-speedup \
    \
    && echo 'DPkg::Post-Invoke { "rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true"; };' > /etc/apt/apt.conf.d/docker-clean \
    && echo 'APT::Update::Post-Invoke { "rm -f /var/cache/apt/archives/*.deb /var/cache/apt/archives/partial/*.deb /var/cache/apt/*.bin || true"; };' >> /etc/apt/apt.conf.d/docker-clean \
    && echo 'Dir::Cache::pkgcache ""; Dir::Cache::srcpkgcache "";' >> /etc/apt/apt.conf.d/docker-clean \
    \
    && echo 'Acquire::Languages "none";' > /etc/apt/apt.conf.d/docker-no-languages \
    \
    && echo 'Acquire::GzipIndexes "true"; Acquire::CompressionTypes::Order:: "gz";' > /etc/apt/apt.conf.d/docker-gzip-indexes

# delete all the apt list files since they're big and get stale quickly
RUN rm -rf /var/lib/apt/lists/*
# this forces "apt-get update" in dependent images, which is also good

# enable the universe
RUN sed -i 's/^#\s*\(deb.*universe\)$/\1/g' /etc/apt/sources.list

# upgrade packages for now, since the tarballs aren't updated frequently enough
RUN apt-get update && apt-get dist-upgrade -y && rm -rf /var/lib/apt/lists/*

# overwrite this with 'CMD []' in a dependent Dockerfile
CMD ["/bin/bash"]

因此，查看Dockerfile，我认为14.04更大的主要原因是它们起始的基础tarball更大。 12.04的 tarball约为39MB，而14.04的 tarball约为66MB。您可以下载并解压缩它们，以获取它们的实际大小，但是我认为这可以帮助您开始了解。

可以使用 docker history命令确认:

$ docker history ubuntu:12.04
IMAGE               CREATED             CREATED BY                                      SIZE
b45a6cbea6d1        6 days ago          /bin/sh -c #(nop) CMD [/bin/bash]               0 B
acc75c8f0e1d        6 days ago          /bin/sh -c apt-get update && apt-get dist-upg   8.5 MB
ae9570f7a92a        6 days ago          /bin/sh -c sed -i 's/^#\s*\(deb.*universe\)$/   1.911 kB
4e284c9e0a9e        6 days ago          /bin/sh -c rm -rf /var/lib/apt/lists/*          0 B
3327dfd9dc7d        6 days ago          /bin/sh -c echo '#!/bin/sh' > /usr/sbin/polic   156.2 kB
0b825e3a3d82        6 days ago          /bin/sh -c #(nop) ADD file:f66a301611d5f2b8e4   103.7 MB
511136ea3c5a        16 months ago                                                       0 B

$ docker history ubuntu:14.04
IMAGE               CREATED             CREATED BY                                      SIZE
6b4e8a7373fe        6 days ago          /bin/sh -c #(nop) CMD [/bin/bash]               0 B
c900195dcbf3        6 days ago          /bin/sh -c apt-get update && apt-get dist-upg   2.178 MB
8b1c48305638        6 days ago          /bin/sh -c sed -i 's/^#\s*\(deb.*universe\)$/   1.895 kB
25c4824a5268        6 days ago          /bin/sh -c rm -rf /var/lib/apt/lists/*          0 B
67b66f26d423        6 days ago          /bin/sh -c echo '#!/bin/sh' > /usr/sbin/polic   194.5 kB
b18d0a2076a1        6 days ago          /bin/sh -c #(nop) ADD file:57743b1a50a2440168   192.6 MB
511136ea3c5a        16 months ago                                                       0 B