看来yum的依赖项解析的行为有所不同，具体取决于它是从Dockerfile的RUN语句调用还是从docker run调用。
考虑这个Dockerfile：
FROM themattrix/centos5-vault-i386
RUN rpm -i http://www.tuxad.com/rpms/tuxad-release-5-1.noarch.rpm
RUN yum update -y
docker build在最后一个命令上失败。完整输出包含在下面，但基本上yum选择i386和x86_64的包。
但是从docker run运行相同的命令是有效的！没有选择x86_64的软件包。
docker run --rm themattrix/centos5-vault-i386 sh -c "
rpm -i http://www.tuxad.com/rpms/tuxad-release-5-1.noarch.rpm &&
yum update -y"
什么可以解释这种奇怪的行为？
以及如何构建Dockerfile？
环境
$ uname -srmp
Darwin 17.7.0 x86_64 i386
$ docker -v
Docker version 18.09.2, build 6247962
docker build的输出
$ docker build .
Sending build context to Docker daemon 6.656kB
Step 1/3 : FROM themattrix/centos5-vault-i386
---> 5706f03d3346
Step 2/3 : RUN rpm -i http://www.tuxad.com/rpms/tuxad-release-5-1.noarch.rpm
---> Using cache
---> ee89f27432c1
Step 3/3 : RUN yum update -y
---> Running in 19e822b9dccc
Loaded plugins: fastestmirror
Determining fastest mirrors
* epel: ftp-stud.hs-esslingen.de
Reducing CentOS-5 - libselinux to included packages only
Finished
Setting up Update Process
Resolving Dependencies
--> Running transaction check
--> Processing Dependency: libselinux = 1.33.4-5.7.el5 for package: libselinux-python
--> Processing Dependency: libselinux = 1.33.4-5.7.el5 for package: libselinux-utils
---> Package libselinux.i386 0:1.33.4-5.7.el5.centos set to be updated
---> Package libselinux-devel.i386 0:1.33.4-5.7.el5.centos set to be updated
---> Package tuxad-release.noarch 0:5-7 set to be updated
--> Running transaction check
---> Package libselinux.x86_64 0:1.33.4-5.7.el5 set to be updated
--> Processing Dependency: libc.so.6(GLIBC_2.2.5)(64bit) for package: libselinux
--> Processing Dependency: ld-linux-x86-64.so.2(GLIBC_2.3)(64bit) for package: libselinux
--> Processing Dependency: ld-linux-x86-64.so.2()(64bit) for package: libselinux
--> Processing Dependency: libc.so.6(GLIBC_2.3)(64bit) for package: libselinux
--> Processing Dependency: libc.so.6(GLIBC_2.4)(64bit) for package: libselinux
--> Processing Dependency: libc.so.6(GLIBC_2.3.4)(64bit) for package: libselinux
--> Processing Dependency: libdl.so.2()(64bit) for package: libselinux
--> Processing Dependency: libc.so.6()(64bit) for package: libselinux
--> Processing Dependency: libsepol.so.1()(64bit) for package: libselinux
--> Running transaction check
---> Package glibc.x86_64 0:2.5-123.el5_11.3 set to be updated
---> Package libsepol.x86_64 0:1.15.2-3.el5 set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Updating:
libselinux i386 1.33.4-5.7.el5.centos libselinux 77 k
libselinux-devel i386 1.33.4-5.7.el5.centos libselinux 144 k
tuxad-release noarch 5-7 tuxad 13 k
Installing for dependencies:
glibc x86_64 2.5-123.el5_11.3 updates 4.8 M
libselinux x86_64 1.33.4-5.7.el5 base 78 k
libsepol x86_64 1.15.2-3.el5 base 131 k
Transaction Summary
================================================================================
Install 3 Package(s)
Upgrade 3 Package(s)
Total download size: 5.2 M
Downloading Packages:
--------------------------------------------------------------------------------
Total 925 kB/s | 5.2 MB 00:05
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID a95f6f37
Importing GPG key 0xA95F6F37 "Frank W. Bergmann (tuxad.com) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-TUXAD-A95F6F37
Running rpm_check_debug
ERROR with rpm_check_debug vs depsolve:
libselinux is needed by (installed) libselinux-utils-1.33.4-5.7.el5.i386
libselinux is needed by (installed) libselinux-python-1.33.4-5.7.el5.i386
Complete!
(1, [u'Please report this error in http://bugs.centos.org/yum5bug'])
The command '/bin/sh -c yum update -y' returned a non-zero code: 1
docker run的输出
$ docker run --rm themattrix/centos5-vault-i386 sh -c "rpm -i http://www.tuxad.com/rpms/tuxad-release-5-1.noarch.rpm && yum update -y"
warning: /var/tmp/rpm-xfer.ZSEYyZ: Header V3 DSA signature: NOKEY, key ID a95f6f37
Loaded plugins: fastestmirror
Determining fastest mirrors
* epel: ftp-stud.hs-esslingen.de
Reducing CentOS-5 - libselinux to included packages only
Finished
Setting up Update Process
Resolving Dependencies
--> Running transaction check
---> Package curl.i386 0:7.15.5-17.el5_11.1 set to be updated
--> Processing Dependency: libcrypto.so.10(OPENSSL_1.0.1) for package: curl
--> Processing Dependency: libssl.so.10 for package: curl
--> Processing Dependency: libcrypto.so.10(libcrypto.so.10) for package: curl
--> Processing Dependency: libcrypto.so.10 for package: curl
--> Processing Dependency: libssl.so.10(libssl.so.10) for package: curl
---> Package kernel-headers.i386 0:2.6.18-419.el5 set to be updated
---> Package libselinux.i386 0:1.33.4-5.7.el5.centos set to be updated
---> Package libselinux-devel.i386 0:1.33.4-5.7.el5.centos set to be updated
---> Package libselinux-python.i386 0:1.33.4-5.7.el5.centos set to be updated
---> Package libselinux-utils.i386 0:1.33.4-5.7.el5.centos set to be updated
---> Package openldap.i386 0:2.3.43-29.el5_11.openssl1 set to be updated
---> Package openssl.i686 0:0.9.8e-40.el5_11.1 set to be updated
---> Package openssl-devel.i386 0:0.9.8e-40.el5_11.1 set to be updated
---> Package tuxad-release.noarch 0:5-7 set to be updated
---> Package tzdata.i386 0:2017b-1.el5 set to be updated
---> Package wget.i386 0:1.11.4-3.el5_11.2.1 set to be updated
--> Running transaction check
---> Package openssl1.i686 0:1.0.1e-57.1.el5_11 set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
================================================================================
Package Arch Version Repository Size
================================================================================
Updating:
curl i386 7.15.5-17.el5_11.1 tuxad 893 k
kernel-headers i386 2.6.18-419.el5 updates 1.5 M
libselinux i386 1.33.4-5.7.el5.centos libselinux 77 k
libselinux-devel i386 1.33.4-5.7.el5.centos libselinux 144 k
libselinux-python i386 1.33.4-5.7.el5.centos libselinux 73 k
libselinux-utils i386 1.33.4-5.7.el5.centos libselinux 55 k
openldap i386 2.3.43-29.el5_11.openssl1 tuxad 717 k
openssl i686 0.9.8e-40.el5_11.1 tuxad 2.9 M
openssl-devel i386 0.9.8e-40.el5_11.1 tuxad 1.9 M
tuxad-release noarch 5-7 tuxad 13 k
tzdata i386 2017b-1.el5 updates 757 k
wget i386 1.11.4-3.el5_11.2.1 tuxad 593 k
Installing for dependencies:
openssl1 i686 1.0.1e-57.1.el5_11 tuxad 3.5 M
Transaction Summary
================================================================================
Install 1 Package(s)
Upgrade 12 Package(s)
Total download size: 13 M
Downloading Packages:
--------------------------------------------------------------------------------
Total 1.4 MB/s | 13 MB 00:09
warning: rpmts_HdrFromFdno: Header V3 DSA signature: NOKEY, key ID a95f6f37
Importing GPG key 0xA95F6F37 "Frank W. Bergmann (tuxad.com) <[email protected]>" from /etc/pki/rpm-gpg/RPM-GPG-KEY-TUXAD-A95F6F37
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Updating : openssl 1/25
Updating : libselinux 2/25
Updating : libselinux-devel 3/25
Updating : openssl-devel 4/25
Updating : tzdata 5/25
Updating : kernel-headers 6/25
Updating : tuxad-release 7/25
Installing : openssl1 8/25
Updating : openldap 9/25
Updating : curl 10/25
Updating : wget 11/25
Updating : libselinux-utils 12/25
Updating : libselinux-python 13/25
Cleanup : libselinux 14/25
Cleanup : tuxad-release 15/25
Cleanup : wget 16/25
Cleanup : libselinux-devel 17/25
Cleanup : openssl-devel 18/25
Cleanup : kernel-headers 19/25
Cleanup : tzdata 20/25
Cleanup : libselinux-utils 21/25
Cleanup : openldap 22/25
Cleanup : curl 23/25
Cleanup : libselinux-python 24/25
Cleanup : openssl 25/25
Dependency Installed:
openssl1.i686 0:1.0.1e-57.1.el5_11
Updated:
curl.i386 0:7.15.5-17.el5_11.1
kernel-headers.i386 0:2.6.18-419.el5
libselinux.i386 0:1.33.4-5.7.el5.centos
libselinux-devel.i386 0:1.33.4-5.7.el5.centos
libselinux-python.i386 0:1.33.4-5.7.el5.centos
libselinux-utils.i386 0:1.33.4-5.7.el5.centos
openldap.i386 0:2.3.43-29.el5_11.openssl1
openssl.i686 0:0.9.8e-40.el5_11.1
openssl-devel.i386 0:0.9.8e-40.el5_11.1
tuxad-release.noarch 0:5-7
tzdata.i386 0:2017b-1.el5
wget.i386 0:1.11.4-3.el5_11.2.1
Complete!
原因是包管理器依赖于内核提供的信息（通过uname(2)）来决定它应该安装哪个版本的包（针对哪个目标体系结构）。虽然你的基本图像里面有i386环境，你仍然在x86_64内核上运行构建，所以事情变得有点棘手。
当您使用docker run运行容器时，您将通过入口点linux32 - 一个小程序，要求内核假装它在i386硬件上运行。但是，当你运行docker build时，RUNs不使用入口点，所以yum看到它在x86_64内核上运行，因此混乱了平台。您可以查看this answer以获得更详细的说明;问题非常相似。
要正确构建图像（仅安装i386软件包），请在yum下的RUNs中运行linux32和其他体系结构敏感命令，例如：
RUN linux32 yum update -y