服务器评测
YUM是RHEL系统中提供的一个安装，卸载和搜索软件包的工具。它能做的不仅仅是安装、卸载软件包，它能做的还有更多，下面我们将在本文中为你展示。
YUM可以自动安装软件包的依赖包，例如当你使用yum安装httpd时，它还会自动安装https apache server以及它依赖的软件包。通过rpm软件包安装时就没有这么方便咯（译注：就是不会自动处理软件包依赖问题咯！），你必须下载所有它依赖的软件包，然后依序安装它们。
yum工具从远端服务器上的软件仓库（通常由OS提供商提供）获取软件包的信息。一个软件仓库是能在特定架构上运行的一系列rpm软件包的集合。例如，对于32位和64位系统各有一个软件仓库，还有针对RHEL5以及RHEL6的软件仓库。你也可以建立一个本地仓库，配置你的yum让其从你的本地仓库里搜索安装软件包。在接下来的例子中，我将向你展示除了安装和卸载软件，yum还可以做的其它事情。为方便理解，我将在我的Amazon EC2 RHEL 6.4服务器上使用httpd软件包为例。
从软件仓库里搜索软件包
# yum search httpd Loaded plugins: amazon-id, rhui-lb, security ==================== N/S Matched: httpd ========== httpd.x86_64 : Apache HTTP Server httpd-devel.i686 : Development interfaces for the Apache HTTP server httpd-devel.x86_64 : Development interfaces for the Apache HTTP server httpd-manual.noarch : Documentation for the Apache HTTP server httpd-tools.x86_64 : Tools for use with the Apache HTTP Server mod_dav_svn.x86_64 : Apache httpd module for Subversion server mod_dnssd.x86_64 : An Apache HTTPD module which adds Zeroconf support
想获得详细的输出信息，可以使用下面的命令：
# yum provides httpd Loaded plugins: amazon-id, rhui-lb, security httpd-2.2.15-26.el6.x86_64 : Apache HTTP Server Repo : rhui-REGION-rhel-server-releases Matched from:
yum provides httpd在软件仓库里搜索含有httpd的软件包。
提供所有软件组列表
# yum grouplist
以上命令将为你显示已经安装的以及可用的软件组。你可以使用软件组安装选项来安装其中一个软件组。例如，我们将安装一个PHP Support的软件组。这个软件组内包含需要的PHP软件包。
# yum groupinstall PHP Support Loaded plugins: amazon-id, downloadonly, rhui-lb, security Setting up Group Process Warning: Group Support does not exist. Resolving Dependencies -> Running transaction check --> Package php.x86_64 0:5.3.3-23.el6_4 will be installed -> Processing Dependency: php-common(x86-64) = 5.3.3-23.el6_4 for package: php-5.3.3-23.el6_4.x86_64 -> Processing Dependency: php-cli(x86-64) = 5.3.3-23.el6_4 for package: php-5.3.3-23.el6_4.x86_64 --> Package php-gd.x86_64 0:5.3.3-23.el6_4 will be installed -> Processing Dependency: libXpm.so.4()(64bit) for package: php-gd-5.3.3-23.el6_4.x86_64 --> Package php-pdo.x86_64 0:5.3.3-23.el6_4 will be installed --> Package php-pear.noarch 1:1.9.4-4.el6 will be installed --> Package php-xml.x86_64 0:5.3.3-23.el6_4 will be installed -> Running transaction check --> Package libXpm.x86_64 0:3.5.10-2.el6 will be installed --> Package php-cli.x86_64 0:5.3.3-23.el6_4 will be installed --> Package php-common.x86_64 0:5.3.3-23.el6_4 will be installed -> Finished Dependency Resolution Dependencies Resolved ================================================== Package Arch Version Repository Size ================================================== Installing: php x86_64 5.3.3-23.el6_4 rhui-REGION-rhel-server-releases 1.1 M php-gd x86_64 5.3.3-23.el6_4 rhui-REGION-rhel-server-releases 106 k php-pdo x86_64 5.3.3-23.el6_4 rhui-REGION-rhel-server-releases 75 k php-pear noarch 1:1.9.4-4.el6 rhui-REGION-rhel-server-releases 393 k php-xml x86_64 5.3.3-23.el6_4 rhui-REGION-rhel-server-releases 103 k Installing for dependencies: libXpm x86_64 3.5.10-2.el6 rhui-REGION-rhel-server-releases 51 k php-cli x86_64 5.3.3-23.el6_4 rhui-REGION-rhel-server-releases 2.2 M php-common x86_64 5.3.3-23.el6_4 rhui-REGION-rhel-server-releases 524 k Transaction Summary ================================================== Install 8 Package(s) Total download size: 4.5 M Installed size: 16 M Is this ok [y/N]: y Downloading Packages: (1/8): libXpm-3.5.10-2.el6.x86_64.rpm | 51 kB 00:00 (2/8): php-5.3.3-23.el6_4.x86_64.rpm | 1.1 MB 00:00 (3/8): php-cli-5.3.3-23.el6_4.x86_64.rpm | 2.2 MB 00:00 (4/8): php-common-5.3.3-23.el6_4.x86_64.rpm | 524 kB 00:00 (5/8): php-gd-5.3.3-23.el6_4.x86_64.rpm | 106 kB 00:00 (6/8): php-pdo-5.3.3-23.el6_4.x86_64.rpm | 75 kB 00:00 (7/8): php-pear-1.9.4-4.el6.noarch.rpm | 393 kB 00:00 (8/8): php-xml-5.3.3-23.el6_4.x86_64.rpm | 103 kB 00:00 ----------------------------------------------- Total 2.9 MB/s | 4.5 MB 00:01 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Installing : php-common-5.3.3-23.el6_4.x86_64 1/8 Installing : php-cli-5.3.3-23.el6_4.x86_64 2/8 Installing : libXpm-3.5.10-2.el6.x86_64 3/8 Installing : php-gd-5.3.3-23.el6_4.x86_64 4/8 Installing : 1:php-pear-1.9.4-4.el6.noarch 5/8 Installing : php-5.3.3-23.el6_4.x86_64 6/8 Installing : php-xml-5.3.3-23.el6_4.x86_64 7/8 Installing : php-pdo-5.3.3-23.el6_4.x86_64 8/8 Verifying : 1:php-pear-1.9.4-4.el6.noarch 1/8 Verifying : php-xml-5.3.3-23.el6_4.x86_64 2/8 Verifying : php-common-5.3.3-23.el6_4.x86_64 3/8 Verifying : libXpm-3.5.10-2.el6.x86_64 4/8 Verifying : php-cli-5.3.3-23.el6_4.x86_64 5/8 Verifying : php-5.3.3-23.el6_4.x86_64 6/8 Verifying : php-pdo-5.3.3-23.el6_4.x86_64 7/8 Verifying : php-gd-5.3.3-23.el6_4.x86_64 8/8 Installed: php.x86_64 0:5.3.3-23.el6_4 php-gd.x86_64 0:5.3.3-23.el6_4 php-pdo.x86_64 0:5.3.3-23.el6_4 php-pear.noarch 1:1.9.4-4.el6 php-xml.x86_64 0:5.3.3-23.el6_4 Dependency Installed: libXpm.x86_64 0:3.5.10-2.el6 php-cli.x86_64 0:5.3.3-23.el6_4 php-common.x86_64 0:5.3.3-23.el6_4 Complete!
使用YUM安装软件包
可以使用yum install命令安装软件包，如下所示：
# yum install httpd Loaded plugins: amazon-id, rhui-lb, security Setting up Install Process Resolving Dependencies -> Running transaction check --> Package httpd.x86_64 0:2.2.15-29.el6_4 will be installed -> Processing Dependency: httpd-tools = 2.2.15-29.el6_4 for package: httpd-2.2.15-29.el6_4.x86_64 -> Processing Dependency: apr-util-ldap for package: httpd-2.2.15-29.el6_4.x86_64 -> Processing Dependency: libaprutil-1.so.0()(64bit) for package: httpd-2.2.15-29.el6_4.x86_64 -> Processing Dependency: libapr-1.so.0()(64bit) for package: httpd-2.2.15-29.el6_4.x86_64 -> Running transaction check --> Package apr.x86_64 0:1.3.9-5.el6_2 will be installed --> Package apr-util.x86_64 0:1.3.9-3.el6_0.1 will be installed --> Package apr-util-ldap.x86_64 0:1.3.9-3.el6_0.1 will be installed --> Package httpd-tools.x86_64 0:2.2.15-29.el6_4 will be installed -> Finished Dependency Resolution Dependencies Resolved ====================================================== Package Arch Version Repository Size ====================================================== Installing: httpd x86_64 2.2.15-29.el6_4 rhui-REGION-rhel-server-releases 821 k Installing for dependencies: apr x86_64 1.3.9-5.el6_2 rhui-REGION-rhel-server-releases 123 k apr-util x86_64 1.3.9-3.el6_0.1 rhui-REGION-rhel-server-releases 87 k apr-util-ldap x86_64 1.3.9-3.el6_0.1 rhui-REGION-rhel-server-releases 15 k httpd-tools x86_64 2.2.15-29.el6_4 rhui-REGION-rhel-server-releases 73 k Transaction Summary ====================================================== Install 5 Package(s) Total download size: 1.1 M Installed size: 3.6 M Is this ok [y/N]: y
如你所见，在安装httpd时yum安装了额外的软件包。这称为yum完成的依赖包解析。
假如你不想让yum弹出[y/N]选项，可以使用yum install -y httpd
使用yum update 命令更新一个已存在的软件包
# yum update httpd Loaded plugins: amazon-id, rhui-lb, security Setting up Update Process No Packages marked for Update
这意味着你系统中安装的httpd软件包已经是yum软件仓库里的最新版本的了。
更多详情见请继续阅读下一页的精彩内容： http://www.linuxidc.com/Linux/2013-11/92971p2.htm
推荐阅读：
配置EPEL YUM源 http://www.linuxidc.com/Linux/2012-10/71850.htm
RedHat 本地yum源配置 http://www.linuxidc.com/Linux/2012-11/75127.htm
RedHat Linux 本地yum源的配置 http://www.linuxidc.com/Linux/2013-08/88217.htm
RedHat 6.2 Linux修改yum源免费使用CentOS源 http://www.linuxidc.com/Linux/2013-07/87383.htm
更多RedHat相关信息见RedHat 专题页面 http://www.linuxidc.com/topicnews.aspx?tid=10
更新服务器上所有的软件包
# yum update
以上命令将系统上的所有软件包更新到最新版本，包括内核软件包，这意味着你的OS更新到了RHEL提供的最新版本了。
下载RPM软件包但是不安装
可以使用yum从RHEL或者CentOS的软件仓库里下载RPM软件包但是不安装。你首先需要下载一个插件让yum只下载rpm软件包而不安装。插件名字叫downloadonly，可以通过yum安装，如下所示：
# yum install yum-downloadonly Loaded plugins: amazon-id, rhui-lb, security Setting up Install Process Resolving Dependencies -> Running transaction check --> Package yum-plugin-downloadonly.noarch 0:1.1.30-14.el6 will be installed -> Finished Dependency Resolution Dependencies Resolved ==================================================== Package Arch Version Repository Size ==================================================== Installing: yum-plugin-downloadonly noarch 1.1.30-14.el6 rhui-REGION-rhel-server-releases 20 k Transaction Summary ==================================================== Install 1 Package(s) Total download size: 20 k Installed size: 21 k Is this ok [y/N]: y Downloading Packages: yum-plugin-downloadonly-1.1.30-14.el6.noarch.rpm | 20 kB 00:00 Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Installing : yum-plugin-downloadonly-1.1.30-14.el6.noarch 1/1 Verifying : yum-plugin-downloadonly-1.1.30-14.el6.noarch 1/1 Installed: yum-plugin-downloadonly.noarch 0:1.1.30-14.el6 Complete!
现在你就可以从软件仓库里只下载软件包而不安装了，命令如下：
# yum install httpd-devel -downloadonly
默认情况下软件包会被下载到/var/cache/yum/目录，但是你可以添加额外选项将其下载到指定位置
# yum install httpd-devel -downloadonly -downloaddir=/opt
假如你有一个rpm软件包但是没有它所依赖的软件包，你不知道到哪去得到它所依赖的软件包。你仍然可以通过yum安装这个rpm软件包，并从软件仓库里得到它所依赖的软件包。让我们安装刚刚下载的httpd-devel-2.2.15-29.el64.x8664 RPM软件包。
# yum localinstall /opt/httpd-devel-2.2.15-29.el6_4.x86_64.rpm Loaded plugins: amazon-id, downloadonly, rhui-lb, security Setting up Local Package Process Examining /opt/httpd-devel-2.2.15-29.el6_4.x86_64.rpm: httpd-devel-2.2.15-29.el6_4.x86_64 Marking /opt/httpd-devel-2.2.15-29.el6_4.x86_64.rpm to be installed Resolving Dependencies -> Running transaction check --> Package httpd-devel.x86_64 0:2.2.15-29.el6_4 will be installed -> Processing Dependency: apr-devel for package: httpd-devel-2.2.15-29.el6_4.x86_64 -> Processing Dependency: apr-util-devel for package: httpd-devel-2.2.15-29.el6_4.x86_64 -> Running transaction check --> Package apr-devel.x86_64 0:1.3.9-5.el6_2 will be installed --> Package apr-util-devel.x86_64 0:1.3.9-3.el6_0.1 will be installed -> Processing Dependency: openldap-devel for package: apr-util-devel-1.3.9-3.el6_0.1.x86_64 -> Processing Dependency: expat-devel for package: apr-util-devel-1.3.9-3.el6_0.1.x86_64 -> Processing Dependency: db4-devel for package: apr-util-devel-1.3.9-3.el6_0.1.x86_64 -> Running transaction check --> Package db4-devel.x86_64 0:4.7.25-18.el6_4 will be installed -> Processing Dependency: db4-cxx = 4.7.25-18.el6_4 for package: db4-devel-4.7.25-18.el6_4.x86_64 -> Processing Dependency: db4 = 4.7.25-18.el6_4 for package: db4-devel-4.7.25-18.el6_4.x86_64 -> Processing Dependency: libdb_cxx-4.7.so()(64bit) for package: db4-devel-4.7.25-18.el6_4.x86_64 --> Package expat-devel.x86_64 0:2.0.1-11.el6_2 will be installed --> Package openldap-devel.x86_64 0:2.4.23-32.el6_4.1 will be installed -> Processing Dependency: cyrus-sasl-devel >= 2.1 for package: openldap-devel-2.4.23-32.el6_4.1.x86_64 -> Running transaction check --> Package cyrus-sasl-devel.x86_64 0:2.1.23-13.el6_3.1 will be installed --> Package db4.x86_64 0:4.7.25-17.el6 will be updated -> Processing Dependency: db4 = 4.7.25-17.el6 for package: db4-utils-4.7.25-17.el6.x86_64 --> Package db4.x86_64 0:4.7.25-18.el6_4 will be an update --> Package db4-cxx.x86_64 0:4.7.25-18.el6_4 will be installed -> Running transaction check --> Package db4-utils.x86_64 0:4.7.25-17.el6 will be updated --> Package db4-utils.x86_64 0:4.7.25-18.el6_4 will be an update -> Finished Dependency Resolution Dependencies Resolved =================================================== Package Arch Version Repository Size =================================================== Installing: httpd-devel x86_64 2.2.15-29.el6_4 /httpd-devel-2.2.15-29.el6_4.x86_64 526 k Installing for dependencies: apr-devel x86_64 1.3.9-5.el6_2 rhui-REGION-rhel-server-releases 176 k apr-util-devel x86_64 1.3.9-3.el6_0.1 rhui-REGION-rhel-server-releases 69 k cyrus-sasl-devel x86_64 2.1.23-13.el6_3.1 rhui-REGION-rhel-server-releases 302 k db4-cxx x86_64 4.7.25-18.el6_4 rhui-REGION-rhel-server-releases 588 k db4-devel x86_64 4.7.25-18.el6_4 rhui-REGION-rhel-server-releases 6.6 M expat-devel x86_64 2.0.1-11.el6_2 rhui-REGION-rhel-server-releases 120 k openldap-devel x86_64 2.4.23-32.el6_4.1 rhui-REGION-rhel-server-releases 1.1 M Updating for dependencies: db4 x86_64 4.7.25-18.el6_4 rhui-REGION-rhel-server-releases 563 k db4-utils x86_64 4.7.25-18.el6_4 rhui-REGION-rhel-server-releases 130 k Transaction Summary =============================================== Install 8 Package(s) Upgrade 2 Package(s) Total size: 10 M Is this ok [y/N]: y Downloading Packages: Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Updating : db4-4.7.25-18.el6_4.x86_64 1/12 Installing : apr-devel-1.3.9-5.el6_2.x86_64 2/12 Installing : expat-devel-2.0.1-11.el6_2.x86_64 3/12 Installing : db4-cxx-4.7.25-18.el6_4.x86_64 4/12 Installing : db4-devel-4.7.25-18.el6_4.x86_64 5/12 Installing : cyrus-sasl-devel-2.1.23-13.el6_3.1.x86_64 6/12 Installing : openldap-devel-2.4.23-32.el6_4.1.x86_64 7/12 Installing : apr-util-devel-1.3.9-3.el6_0.1.x86_64 8/12 Installing : httpd-devel-2.2.15-29.el6_4.x86_64 9/12 Updating : db4-utils-4.7.25-18.el6_4.x86_64 10/12 Cleanup : db4-utils-4.7.25-17.el6.x86_64 11/12 Cleanup : db4-4.7.25-17.el6.x86_64 12/12 Verifying : apr-devel-1.3.9-5.el6_2.x86_64 1/12 Verifying : cyrus-sasl-devel-2.1.23-13.el6_3.1.x86_64 2/12 Verifying : apr-util-devel-1.3.9-3.el6_0.1.x86_64 3/12 Verifying : db4-cxx-4.7.25-18.el6_4.x86_64 4/12 Verifying : httpd-devel-2.2.15-29.el6_4.x86_64 5/12 Verifying : openldap-devel-2.4.23-32.el6_4.1.x86_64 6/12 Verifying : expat-devel-2.0.1-11.el6_2.x86_64 7/12 Verifying : db4-devel-4.7.25-18.el6_4.x86_64 8/12 Verifying : db4-4.7.25-18.el6_4.x86_64 9/12 Verifying : db4-utils-4.7.25-18.el6_4.x86_64 10/12 Verifying : db4-4.7.25-17.el6.x86_64 11/12 Verifying : db4-utils-4.7.25-17.el6.x86_64 12/12 Installed: httpd-devel.x86_64 0:2.2.15-29.el6_4 Dependency Installed: apr-devel.x86_64 0:1.3.9-5.el6_2 apr-util-devel.x86_64 0:1.3.9-3.el6_0.1 cyrus-sasl-devel.x86_64 0:2.1.23-13.el6_3.1 db4-cxx.x86_64 0:4.7.25-18.el6_4 db4-devel.x86_64 0:4.7.25-18.el6_4 expat-devel.x86_64 0:2.0.1-11.el6_2 openldap-devel.x86_64 0:2.4.23-32.el6_4.1 Dependency Updated: db4.x86_64 0:4.7.25-18.el6_4 db4-utils.x86_64 0:4.7.25-18.el6_4 Complete!
使用yum卸载软件包
使用 yum remove 卸载软件包。举例如下：
# yum remove httpd Failed to set locale, defaulting to C Loaded plugins: amazon-id, downloadonly, rhui-lb, security Setting up Remove Process Resolving Dependencies -> Running transaction check --> Package httpd.x86_64 0:2.2.15-29.el6_4 will be erased -> Processing Dependency: httpd-mmn = 20051115 for package: php-5.3.3-23.el6_4.x86_64 -> Processing Dependency: httpd = 2.2.15-29.el6_4 for package: httpd-devel-2.2.15-29.el6_4.x86_64 -> Running transaction check --> Package httpd-devel.x86_64 0:2.2.15-29.el6_4 will be erased --> Package php.x86_64 0:5.3.3-23.el6_4 will be erased -> Finished Dependency Resolution Dependencies Resolved ================================================ Package Arch Version Repository Size ================================================ Removing: httpd x86_64 2.2.15-29.el6_4 @rhui-REGION-rhel-server-releases 2.9 M Removing for dependencies: httpd-devel x86_64 2.2.15-29.el6_4 @/httpd-devel-2.2.15-29.el6_4.x86_64 526 k php x86_64 5.3.3-23.el6_4 @rhui-REGION-rhel-server-releases 3.5 M Transaction Summary ================================================ Remove 3 Package(s) Installed size: 7.0 M Is this ok [y/N]: y Downloading Packages: Running rpm_check_debug Running Transaction Test Transaction Test Succeeded Running Transaction Erasing : httpd-devel-2.2.15-29.el6_4.x86_64 1/3 Erasing : php-5.3.3-23.el6_4.x86_64 2/3 Erasing : httpd-2.2.15-29.el6_4.x86_64 3/3 Verifying : httpd-2.2.15-29.el6_4.x86_64 1/3 Verifying : httpd-devel-2.2.15-29.el6_4.x86_64 2/3 Verifying : php-5.3.3-23.el6_4.x86_64 3/3 Removed: httpd.x86_64 0:2.2.15-29.el6_4 Dependency Removed: httpd-devel.x86_64 0:2.2.15-29.el6_4 php.x86_64 0:5.3.3-23.el6_4 Complete!
列出所有安装的软件包
假如你要列出你系统上安装的所有软件包，你可以使用yum list installed命令。这条命令结合grep命令是非常有用的，可以用来检查某个特定的软件包是否已被安装。这与使用rpm -qa命令询问已经安装的软件包相似。
# yum list installed Loaded plugins: amazon-id, downloadonly, rhui-lb, security Installed Packages ConsoleKit.x86_64 0.4.1-3.el6 @koji-override-0/$releasever ConsoleKit-libs.x86_64 0.4.1-3.el6 @koji-override-0/$releasever MAKEDEV.x86_64 3.24-6.el6 @koji-override-0/$releasever PyYAML.x86_64 3.10-3.1.el6 @koji-override-0/$releasever Red_Hat_Enterprise_Linux-Release_Notes-6-en-US.noarch 4-2.el6 @koji-override-0/$releasever SDL.x86_64 1.2.14-3.el6 @koji-override-0/$releasever abrt.x86_64 2.0.8-15.el6 @koji-override-0/$releasever abrt-addon-ccpp.x86_64 2.0.8-15.el6 @koji-override-0/$releasever abrt-addon-kerneloops.x86_64 2.0.8-15.el6 @koji-override-0/$releasever abrt-addon-Python.x86_64 2.0.8-15.el6 @koji-override-0/$releasever abrt-cli.x86_64 2.0.8-15.el6 @koji-override-0/$releasever abrt-libs.x86_64 2.0.8-15.el6 @koji-override-0/$releasever abrt-tui.x86_64 2.0.8-15.el6 @koji-override-0/$releasever acl.x86_64 2.2.49-6.el6 @koji-override-0/$releasever acpid.x86_64 1.0.10-2.1.el6 @koji-override-0/$releasever aic94xx-firmware.noarch 30-2.el6 @koji-override-0/$releasever . . Output Truncated.
列出可用的软件库，通过它们可以查询、安装和更新软件包
# yum repolist Loaded plugins: amazon-id, downloadonly, rhui-lb, security repo id repo name status rhui-REGION-client-config-server-6 Red Hat Update Infrastructure 2.0 Client Configuration Server 6 4 rhui-REGION-rhel-server-releases Red Hat Enterprise Linux Server 6 (RPMs) 10994 rhui-REGION-rhel-server-releases-optional Red Hat Enterprise Linux Server 6 Optional (RPMs) 6250 repolist: 17248
更多RedHat相关信息见RedHat 专题页面 http://www.linuxidc.com/topicnews.aspx?tid=10
