centos docker 镜像太大

Question

我用这个 Dockerfile 构建了一个镜像。

FROM sanmingzi/ruby:1.9.3

RUN yum -y install gcc ruby-devel zlib-devel \
  && yum -y remove gcc ruby-devel zlib-devel \
  && yum -y clean all \
  && rm -rf /var/cache/yum \
  && rm -rf /var/tmp/*

我希望新图像的大小与 sanmingzi/ruby:1.9.3 相同，但我错了。比旧图像大约有 50MB。我使用docker history 来显示细节。

IMAGE               CREATED             CREATED BY                                      SIZE
b154156f1053        4 minutes ago       /bin/sh -c yum -y install gcc ruby-devel z...   55.4MB

Answer 1

当我们在 CentOS 镜像中安装 gcc、ruby-devel 和 zlib-devel 时，还会安装或升级很多其他依赖包：

Dependencies Resolved

================================================================================
 Package                Arch       Version                    Repository   Size
================================================================================
Installing:
 gcc                    x86_64     4.8.5-16.el7_4.2           updates      16 M
 ruby-devel             x86_64     2.0.0.648-33.el7_4         updates     131 k
Installing for dependencies:
 cpp                    x86_64     4.8.5-16.el7_4.2           updates     6.0 M
 glibc-devel            x86_64     2.17-196.el7_4.2           updates     1.1 M
 glibc-headers          x86_64     2.17-196.el7_4.2           updates     676 k
 kernel-headers         x86_64     3.10.0-693.21.1.el7        updates     6.0 M
 libgomp                x86_64     4.8.5-16.el7_4.2           updates     154 k
 libmpc                 x86_64     1.0.1-3.el7                base         51 k
 mpfr                   x86_64     3.1.1-4.el7                base        203 k
 ruby                   x86_64     2.0.0.648-33.el7_4         updates      71 k
 ruby-irb               noarch     2.0.0.648-33.el7_4         updates      92 k
 ruby-libs              x86_64     2.0.0.648-33.el7_4         updates     2.8 M
 rubygem-bigdecimal     x86_64     1.2.0-33.el7_4             updates      83 k
 rubygem-io-console     x86_64     0.4.2-33.el7_4             updates      54 k
 rubygem-json           x86_64     1.7.7-33.el7_4             updates      79 k
 rubygem-psych          x86_64     2.0.0-33.el7_4             updates      82 k
 rubygem-rdoc           noarch     4.0.0-33.el7_4             updates     322 k
 rubygems               noarch     2.0.14.1-33.el7_4          updates     219 k
Updating for dependencies:
 libgcc                 x86_64     4.8.5-16.el7_4.2           updates      98 k

Transaction Summary
================================================================================
Install  2 Packages (+16 Dependent packages)
Upgrade             (  1 Dependent package)

之后我们只删除gcc、ruby-devel和zlib-devel：

Dependencies Resolved

================================================================================
 Package             Arch         Version                  Repository      Size
================================================================================
Removing:
 gcc                 x86_64       4.8.5-16.el7_4.2         @updates        37 M
 ruby-devel          x86_64       2.0.0.648-33.el7_4       @updates       337 k
 zlib-devel          x86_64       1.2.7-17.el7             @base          132 k
Removing for dependencies:
 openssl-devel       x86_64       1:1.0.2k-8.el7           @base          3.1 M

Transaction Summary
================================================================================
Remove  3 Packages (+1 Dependent package)

这就是为什么我们的最终图像比原始图像尺寸更大。