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CentOS 8的国内镜像和dnf包管理器dnf(不是毒奶粉与勇士)一直以来是Fedora的包管理工具(从Fedora 22开始成为默认包管理器)，号称是yum的下一代包管理器。
在CentOS 8中也加入了dnf且成为默认的包管理工具，因此CentOS 8中可以使用dnf或yum来管理包。实际上，CentOS 8的yum是dnf的一个软链接：
12$ ls -l /usr/bin/yumlrwxrwxrwx. 1 root root 5 May 14 2019 /usr/bin/yum -> dnf-3
配置CentOS 8 dnf/yum国内镜像在CentOS 7及之前的版本，yum官方仓库一直都是Base库、Extras库、Updates库、centosplus库等。其中Base库是安装CentOS时必须提供的仓库，它提供CentOS安装(比如可以选择安装桌面环境、开发工具等)、运行以及一些常用用户空间程序。
1234567891011121314151617181920$ yum repolist allLoaded plugins: fastestmirrorLoading mirror speeds from cached hostfile * base: mirrors.163.com * epel: mirrors.bfsu.edu.cn * extras: mirrors.163.com * updates: mirrors.163.comrepo id repo name status!base/7/x86_64 CentOS-7 - Base enabled: 10,070base-debuginfo/x86_64 CentOS-7 - Debuginfo disabledbase-source/7 CentOS-7 - Base Sources disabledcentos-kernel/7/x86_64 CentOS LTS Kernels for x86_64 disabledcentosplus/7/x86_64 CentOS-7 - Plus disabledcentosplus-source/7 CentOS-7 - Plus Sources disabled!epel/x86_64 Extra Packages for Enterprise Linux 7 - x86_64 enabled: 13,455!extras/7/x86_64 CentOS-7 - Extras enabled: 413extras-source/7 CentOS-7 - Extras Sources disabled!updates/7/x86_64 CentOS-7 - Updates enabled: 1,134updates-source/7 CentOS-7 - Updates Sources disabledrepolist: 25,072
在CentOS 8中发生了变化，原来的base库被拆分成两部分：AppStream和Base库。安装CentOS 8时必须提供这两个库。
其中：
CentOS 8的Base库提供安装和运行CentOS 8时必须的包，即CentOS核心包。这个仓库中全都是rpm包。
CentOS 8的AppStream库提供常用用户空间程序，它们并不一定是安装和运行CentOS 8所必须的，比如Python包、Perl包等语言包都在AppStream。AppStream中包含rpm包和dnf的模块。
AppStream库中的包一般是用户空间程序包，这些程序的更新速度一般比CentOS系统更新快的多，将它们单独提取到AppStream库，意味着这些程序包和系统相关的包被解绑分开到两个仓库，这可以让系统包和常用程序包分开升级，有利于提供这些程序包的最新的版本。
使用过CentOS的人可能都会庆幸这种改变。最近这些年互联网的发展极为迅速，很多程序包的迭代速度也非常快，以前的CentOS版本中，很多程序的版本往往都非常古老，要升级这些程序包，只能单独配置它们的镜像仓库(相当于是第三方仓库)，甚至很多程序只能自己编译新版本。
在配置CentOS 8仓库时，还有一个PowerTools仓库很可能会用上，它主要用于提供：
其他程序包的依赖包(大量的devel包和lib包)
那些语言的模块或包，比如Perl-DataTime。这意味着，如果不用语言自身的包管理器(比如pip/gem/cpan/npm等)安装它们的模块，就需要启用PowerTools仓库后用yum/dnf来安装
配置CentOS 8的国内镜像仓库和之前CentOS版本倒没什么区别，只是要注意提供AppStream和可能要使用到的PowerTools仓库。
下面是CentOS 8中国内镜像仓库的配置示例：
1234567891011121314151617181920212223242526272829303132333435363738# $tencent=https://mirrors.cloud.tencent.com# $contentdir=centos# $releasever=8[AppStream]name=CentOS-$releasever - AppStreambaseurl=$tencent/$contentdir/$releasever/AppStream/$basearch/os/gpgcheck=0enabled=1[BaseOS]name=CentOS-$releasever - Basebaseurl=$tencent/$contentdir/$releasever/BaseOS/$basearch/os/gpgcheck=0enabled=1[centosplus]name=CentOS-$releasever - Plusbaseurl=$tencent/$contentdir/$releasever/centosplus/$basearch/os/gpgcheck=0enabled=1[extras]name=CentOS-$releasever - Extrasbaseurl=$tencent/$contentdir/$releasever/extras/$basearch/os/gpgcheck=0enabled=1[PowerTools]name=CentOS-$releasever - PowerToolsbaseurl=$tencent/$contentdir/$releasever/PowerTools/$basearch/os/enabled=1gpgcheck=0[epel]name = epel repobaseurl = $tencent/epel/$releasever/Everything/$basearchenabled=1gpgcheck=0
配置国内镜像之后，重建缓存：
12sudo dnf clean allsudo dnf makecache
dnf用法参考手册：https://dnf.readthedocs.io/en/latest/command_ref.html。
dnf和yum的常用用法基本一致，不过dnf支持更多的功能。dnf最典型的功能是支持模块。
123456789101112131415161718192021222324252627282930313233343536373839404142434445464748495051525354555657585960616263646566676869707172737475767778798081828384858687888990919293949596979899100101102103104105106107108109110111112113114115116117118119120121122123124125126127128129130131132133134135136137138$ dnf --help usage: dnf [options] COMMANDList of Main Commands:alias List or create command aliasesautoremove remove all unneeded packages that were originally installed as dependenciescheck check for problems in the packagedbcheck-update check for available package upgradesclean remove cached datadeplist List package's dependencies and what packages provide themdistro-sync synchronize installed packages to the latest available versionsdowngrade Downgrade a packagegroup display, or use, the groups informationhelp display a helpful usage messagehistory display, or use, the transaction historyinfo display details about a package or group of packagesinstall install a package or packages on your systemlist list a package or groups of packagesmakecache generate the metadata cachemark mark or unmark installed packages as installed by user.module Interact with Modules.provides find what package provides the given valuereinstall reinstall a packageremove remove a package or packages from your systemrepolist display the configured software repositoriesrepoquery search for packages matching keywordrepository-packages run commands on top of all packages in given repositorysearch search package details for the given stringshell run an interactive DNF shellswap run an interactive dnf mod for remove and install one specupdateinfo display advisories about packagesupgrade upgrade a package or packages on your systemupgrade-minimal upgrade, but only 'newest' package match which fixes a problem that affects your systemList of Plugin Commands:builddep Install build dependencies for package or spec filechangelog Show changelog data of packagesconfig-manager manage dnf configuration options and repositoriescopr Interact with Copr repositories.debug-dump dump information about installed rpm packages to filedebug-restore restore packages recorded in debug-dump filedebuginfo-install install debuginfo packagesdownload Download package to current directoryneeds-restarting determine updated binaries that need restartingplayground Interact with Playground repository.repoclosure Display a list of unresolved dependencies for repositoriesrepodiff List differences between two sets of repositoriesrepograph Output a full package dependency graph in dot formatrepomanage Manage a directory of rpm packagesreposync download all packages from remote repoOptional arguments: -c [config file], --config [config file] config file location -q, --quiet quiet operation -v, --verbose verbose operation --version show DNF version and exit --installroot [path] set install root --nodocs do not install documentations --noplugins disable all plugins --enableplugin [plugin] enable plugins by name --disableplugin [plugin] disable plugins by name --releasever RELEASEVER override the value of $releasever in config and repo files --setopt SETOPTS set arbitrary config and repo options --skip-broken resolve depsolve problems by skipping packages -h, --help, --help-cmd show command help --allowerasing allow erasing of installed packages to resolve dependencies -b, --best try the best available package versions in transactions. --nobest do not limit the transaction to the best candidate -C, --cacheonly run entirely from system cache, don't update cache -R [minutes], --randomwait [minutes] maximum command wait time -d [debug level], --debuglevel [debug level] debugging output level --debugsolver dumps detailed solving results into files --showduplicates show duplicates, in repos, in list/search commands -e ERRORLEVEL, --errorlevel ERRORLEVEL error output level --obsoletes enables dnf's obsoletes processing logic for upgrade or display capabilities that the package obsoletes for info, list and repoquery --rpmverbosity [debug level name] debugging output level for rpm -y, --assumeyes automatically answer yes for all questions --assumeno automatically answer no for all questions --enablerepo [repo] --disablerepo [repo] --repo [repo], --repoid [repo] enable just specific repositories by an id or a glob, can be specified multiple times --enable, --set-enabled enable repos with config-manager command (automatically saves) --disable, --set-disabled disable repos with config-manager command (automatically saves) -x [package], --exclude [package], --excludepkgs [package] exclude packages by name or glob --disableexcludes [repo], --disableexcludepkgs [repo] disable excludepkgs --repofrompath [repo,path] label and path to additional repository, can be specified multiple times. --noautoremove disable removal of dependencies that are no longer used --nogpgcheck disable gpg signature checking (if RPM policy allows) --color COLOR control whether color is used --refresh set metadata as expired before running the command -4 resolve to IPv4 addresses only -6 resolve to IPv6 addresses only --destdir DESTDIR, --downloaddir DESTDIR set directory to copy packages to --downloadonly only download packages --comment COMMENT add a comment to transaction --bugfix Include bugfix relevant packages, in updates --enhancement Include enhancement relevant packages, in updates --newpackage Include newpackage relevant packages, in updates --security Include security relevant packages, in updates --advisory ADVISORY, --advisories ADVISORY Include packages needed to fix the given advisory, in updates --bzs BUGZILLA Include packages needed to fix the given BZ, in updates --cves CVES Include packages needed to fix the given CVE, in updates --sec-severity {Critical,Important,Moderate,Low}, --secseverity {Critical,Important,Moderate,Low} Include security relevant packages matching the severity, in updates --forcearch ARCH Force the use of an architecture
dnf基本用法这里只介绍和yum差不多的常用的功能，dnf模块相关的后文专门介绍。
清理缓存和重建缓存
12sudo dnf clean [ all ]sudo dnf makecache # 注：不兼容以前yum的用法yum makecache fast
列出已配置的镜像仓库
123456789# 列出已启用(enabled=1)、已禁用或所有已配置仓库dnf repolistdnf repolist --enableddnf repolist --disabled dnf repolist --all# 查看某个或所有仓库的详细信息dnf repolist -vdnf repolist BaseOS -v
列出包
123456789101112131415# 列出所有可获取的包(包括已安装和未安装)，下面等价dnf list # 默认--all选项dnf list --all# 分别列出已安装和未安装的包dnf list --installeddnf list --available# 列出可升级的包，等价dnf list --updatesdnf list --upgradesdnf check-updates# 列出可被移除(已不再被依赖)的包dnf list --autoremove
搜索包
1234567891011# 从列出的包中搜索某个包，使用grep即可dnf list --installed | grep 'net-tools'# 根据pattern匹配包名，它会从包名、包的描述信息中匹配dnf search 'net*tools'# 只从包名匹配dnf repoquery 'net*tools'# 根据文件搜索包dnf provides '*bin/netstat'
查看包的信息
1dnf info net-tools
查看包中包含的文件
12# 属于rpm的用法rpm -ql net-tools
安装和卸载包
1234567891011121314# 下面命令加上-y选项，可以在交互式中自动yes确认# 根据包名安装dnf install net-tools# 根据文件名安装(dnf有而以前yum没有但好用的功能)dnf install /usr/bin/netstatdnf install $(which netstat)# 移除包，同时会移除依赖包dnf remove net-tools# 自动移除已经不被依赖的包dnf autoremove
升级系统中的包
123456789101112# 列出可升级的包，其中check-updates还列出如果升级时必须升级的包# 其他包都不是必须升级的dnf list --updatesdnf list --upgradesdnf check-updates# 升级一个包或所有可升级的包yum upgradeyum upgrade
dnf模块
也就是说，dnf模块将某些具有关联关系的包和它们的版本号绑定在一起。或者，可以将模块看作是带有版本号、可共存、可配置的包组。
dnf模块都由stream提供，例如其中一个官方的stream就是AppStream。
例如，AppStream提供了两个版本的perl dnf模块：
1234567$ dnf module list perlAppStreamName Stream Profiles Summary perl 5.24 common [d], minimal Practical Extraction and Report Language perl 5.26 [d] common [d], minimal Practical Extraction and Report Language Hint: [d]efault, [e]nabled, [x]disabled, [i]nstalled
perl 5.24版本的dnf模块包含的是所有perl 5.24相关的包，perl 5.26包含的是所有perl 5.26相关的包。
关注一下上面输出的两行perl的内容。
它们的模块名(Name)叫做perl，它们来自AppStream，且perl有两个版本的Stream，分别是5.24和5.26，其中5.26后面有个[d]表示这是默认的perl模块，只有标记为[d]或[e]的模块才可以已经启用(激活)的模块，可以安装，否则不可安装。另外，这两个perl模块都有两个Profiles，其中common是默认的profiles，还有一个minimal，Profiles的含义不言自明：配置了哪些rpm包需要被安装。所以，minimal是最小化安装的方式，而common在安装perl模块的时候还会安装一些额外的包。
dnf module用法参考资料：
https://dnf.readthedocs.io/en/latest/conf_ref.html
https://docs.fedoraproject.org/en-US/modularity/
下面截取自dnf help module
123456789101112131415161718192021222324$ dnf help moduleusage: dnf module
列出模块：
1234567# 列出当前系统所有已配置的模块dnf module list# 列出已启用的模块(可直接安装)dnf module list --enabled# 列出已被禁用的模块(不可直接安装，需启用后才可安装)dnf module list --disabled
查看模块信息：
1dnf module info perl
安装、移除模块：
123456789101112131415# 安装默认版本(stream)、默认profilednf module install perl# 指定版本dnf module install perl:5.26# 指定Profilednf module install perl/minimaldnf module install perl:5.26/minimal# 移除模块dnf module remove perldnf module remove perl:5.24dnf module remove perl/minimaldnf module remove perl:5.24/minimal
安装模块的另一种写法：
123dnf install @perldnf install @perl:5.26dnf install @perl:5.26/common
启用、禁用模块：
12dnf module disable perl:5.24dnf module enable perl:5.24
perl版本切换(perl 5.24 -> perl 5.26)：
1234567# 即切换模块，分两步操作# 重置enabled状态，这不会卸载已安装的perl 5.24模块中的包dnf module reset perl# 安装perl:5.26dnf module install perl:5.26