CentOS 7.6.1810 更新提示错误，如何解决？

[哈特比尔波]

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错误：软件包：mono-core-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libm.so.6(GLIBC_2.27)(64bit)
错误：软件包：libmonoboehm-2_0-1-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libm.so.6(GLIBC_2.27)(64bit)
错误：软件包：libmonosgen-2_0-1-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libc.so.6(GLIBC_2.25)(64bit)
错误：软件包：msbuild-libhostfxr-3.0.0.2019.04.16.02.13-0.xamarin.4.epel8.x86_64 (mono-centos8-preview)
需要：libstdc++.so.6(GLIBCXX_3.4.20)(64bit)
错误：软件包：libmonoboehm-2_0-1-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libc.so.6(GLIBC_2.25)(64bit)
错误：软件包：libgdiplus0-6.0.3-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libpng16.so.16()(64bit)
错误：软件包：libgdiplus0-6.0.3-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libgif.so.7()(64bit)
错误：软件包：libmonosgen-2_0-1-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libm.so.6(GLIBC_2.27)(64bit)
错误：软件包：mono-llvm-tools-6.0+mono20190708165219-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libstdc++.so.6(GLIBCXX_3.4.20)(64bit)
错误：软件包：libgdiplus0-6.0.3-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libm.so.6(GLIBC_2.27)(64bit)
错误：软件包：mono-llvm-tools-6.0+mono20190708165219-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libstdc++.so.6(GLIBCXX_3.4.21)(64bit)
错误：软件包：libmono-llvm0-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
需要：libstdc++.so.6(GLIBCXX_3.4.21)(64bit)
错误：软件包：mono-nunit-5.20.1.34-0.xamarin.2.epel7.x86_64 (download.mono-project.com_repo_centos7_)
需要：mono-core = 5.20.1.34
正在删除: mono-core-5.20.1.19-0.xamarin.3.epel7.x86_64 (@download.mono-project.com_repo_centos7_)
mono-core = 5.20.1.19-0.xamarin.3.epel7
更新，由: mono-core-6.6.0.104-0.xamarin.1.epel8.x86_64 (mono-centos8-preview)
mono-core = 6.6.0.104-0.xamarin.1.epel8
可用: mono-core-3.8.0-1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.8.0-1
可用: mono-core-3.10.0-1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.10.0-1
可用: mono-core-3.10.0-2.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.10.0-2
可用: mono-core-3.12.0-0.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.12.0-0
可用: mono-core-3.12.0-1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.12.0-1
可用: mono-core-3.12.0-2.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.12.0-2
可用: mono-core-3.12.1-0.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 3.12.1-0
可用: mono-core-4.0.1-1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.1-1
可用: mono-core-4.0.1-2.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.1-2
可用: mono-core-4.0.1-3.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.1-3
可用: mono-core-4.0.1-4.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.1-4
可用: mono-core-4.0.1.44-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.1.44-0.xamarin.1
可用: mono-core-4.0.2.5-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.2.5-0.xamarin.1
可用: mono-core-4.0.3.20-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.3.20-0.xamarin.1
可用: mono-core-4.0.3.20-0.xamarin.4.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.3.20-0.xamarin.4
可用: mono-core-4.0.4.1-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.4.1-0.xamarin.1
可用: mono-core-4.0.5.1-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.0.5.1-0.xamarin.1
可用: mono-core-4.2.1.102-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.2.1.102-0.xamarin.1
可用: mono-core-4.2.2.30-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.2.2.30-0.xamarin.1
可用: mono-core-4.2.2.30-0.xamarin.2.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.2.2.30-0.xamarin.2
可用: mono-core-4.2.3.4-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.2.3.4-0.xamarin.1
可用: mono-core-4.2.4.4-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.2.4.4-0.xamarin.1
可用: mono-core-4.4.1.0-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.4.1.0-0.xamarin.1
可用: mono-core-4.4.2.11-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.4.2.11-0.xamarin.1
可用: mono-core-4.6.0.245-0.xamarin.4.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.6.0.245-0.xamarin.4
可用: mono-core-4.6.1.3-0.xamarin.2.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.6.1.3-0.xamarin.2
可用: mono-core-4.6.1.5-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.6.1.5-0.xamarin.1
可用: mono-core-4.6.2.7-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.6.2.7-0.xamarin.1
可用: mono-core-4.6.2.16-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.6.2.16-0.xamarin.1
可用: mono-core-4.8.0.495-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.8.0.495-0.xamarin.1
可用: mono-core-4.8.0.520-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.8.0.520-0.xamarin.1
可用: mono-core-4.8.0.524-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.8.0.524-0.xamarin.1
可用: mono-core-4.8.1.0-0.xamarin.1.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 4.8.1.0-0.xamarin.1
可用: mono-core-5.0.0.100-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.0.0.100-0.xamarin.1.epel7
可用: mono-core-5.0.1.1-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.0.1.1-0.xamarin.3.epel7
可用: mono-core-5.2.0.215-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.2.0.215-0.xamarin.3.epel7
可用: mono-core-5.2.0.224-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.2.0.224-0.xamarin.1.epel7
可用: mono-core-5.4.0.201-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.4.0.201-0.xamarin.1.epel7
可用: mono-core-5.4.1.6-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.4.1.6-0.xamarin.1.epel7
可用: mono-core-5.4.1.7-0.xamarin.2.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.4.1.7-0.xamarin.2.epel7
可用: mono-core-5.8.0.108-0.xamarin.2.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.8.0.108-0.xamarin.2.epel7
可用: mono-core-5.8.0.127-0.xamarin.2.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.8.0.127-0.xamarin.2.epel7
可用: mono-core-5.8.0.127-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.8.0.127-0.xamarin.3.epel7
可用: mono-core-5.10.0.140-0.xamarin.2.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.10.0.140-0.xamarin.2.epel7
可用: mono-core-5.10.0.160-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.10.0.160-0.xamarin.1.epel7
可用: mono-core-5.10.1.4-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.10.1.4-0.xamarin.3.epel7
可用: mono-core-5.10.1.20-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.10.1.20-0.xamarin.3.epel7
可用: mono-core-5.10.1.47-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.10.1.47-0.xamarin.3.epel7
可用: mono-core-5.12.0.233-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.12.0.233-0.xamarin.3.epel7
可用: mono-core-5.12.0.301-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.12.0.301-0.xamarin.1.epel7
可用: mono-core-5.14.0.177-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.14.0.177-0.xamarin.1.epel7
可用: mono-core-5.16.0.187-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.16.0.187-0.xamarin.3.epel7
可用: mono-core-5.16.0.220-0.xamarin.4.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.16.0.220-0.xamarin.4.epel7
可用: mono-core-5.18.0.225-0.xamarin.1.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.18.0.225-0.xamarin.1.epel7
可用: mono-core-5.18.0.225-0.xamarin.13.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.18.0.225-0.xamarin.13.epel7
可用: mono-core-5.18.0.240-0.xamarin.2.epel7.x86_64 (download.mono-project.com_repo_centos7_)
mono-core = 5.18.0.240-0.xamarin.2.epel7
可用: mono-core-5.18.0.268-0.xamarin.3.epel7.x86_64 (download.mono-project.com_repo_centos7_