敲入：
yum help
显示如下；
Options:
-h, --help show this help message and exit
-t, --tolerant be tolerant of errors
-C, --cacheonly run entirely from system cache, don't update cache
-c [config file], --config=[config file]
config file location
-R [minutes], --randomwait=[minutes]
maximum command wait time
-d [debug level], --debuglevel=[debug level]
debugging output level
--showduplicates show duplicates, in repos, in list/search commands
-e [error level], --errorlevel=[error level]
error output level
--rpmverbosity=[debug level name]
debugging output level for rpm
-q, --quiet quiet operation
-v, --verbose verbose operation
-y, --assumeyes answer yes for all questions
--assumeno answer no for all questions
--version show Yum version and exit
--installroot=[path] set install root
--enablerepo=[repo] enable one or more repositories (wildcards allowed)
--disablerepo=[repo] disable one or more repositories (wildcards allowed)
-x [package], --exclude=[package]
exclude package(s) by name or glob
--disableexcludes=[repo]
disable exclude from main, for a repo or for
everything
--disableincludes=[repo]
disable includepkgs for a repo or for everything
--obsoletes enable obsoletes processing during updates
--noplugins disable Yum plugins
--nogpgcheck disable gpg signature checking
--disableplugin=[plugin]
disable plugins by name
--enableplugin=[plugin]
enable plugins by name
--skip-broken skip packages with depsolving problems
--color=COLOR control whether color is used
--releasever=RELEASEVER
set value of $releasever in yum config and repo files
--downloadonly don't update, just download
--downloaddir=DLDIR specifies an alternate directory to store packages
--setopt=SETOPTS set arbitrary config and repo options
--bugfix Include bugfix relevant packages, in updates
--security Include security relevant packages, in updates