设置yum工具仅下载不安装rpm包

# yum install yum-downloadonly
Sample output:
Loading "fastestmirror" plugin
Loading "security" plugin
Loading mirror speeds from cached hostfile
* base: centos.mirrors.tds.net
* updates: mirror.myriadnetwork.com
* addons: mirrors.gigenet.com
* extras: holmes.umflint.edu
Setting up Install Process
Parsing package install arguments
Resolving Dependencies
--> Running transaction check
---> Package yum-downloadonly.noarch 0:1.1.10-9.el5.centos set to be updated
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
yum-downloadonly        noarch     1.1.10-9.el5.centos  base              9.0 k
Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)         
Total download size: 9.0 k
Is this ok [y/N]: y
Downloading Packages:
(1/1): yum-downloadonly-1 100% |=========================| 9.0 kB    00:00
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
  Installing: yum-downloadonly             ######################### [1/1]
Installed: yum-downloadonly.noarch 0:1.1.10-9.el5.centos
Complete!How do I download a RPM package only from RHN or CentOS
mirror, without installing it?Download httpd package but don't
install/update, enter:
# yum update httpd -y --downloadonly
By default package will by downloaded and stored in /var/cache/yum/
directory. But, you can specifies an alternate directory to store
packages such as /opt, enter:
# yum update httpd -y --downloadonly --downloaddir=/opt
Sample output:
yum install httpd -y --downloadonly
Loading "downloadonly" plugin
Loading "fastestmirror" plugin
Loading "security" plugin
Loading mirror speeds from cached hostfile
* base: centos.mirrors.mypsh.com
* updates: mirror.steadfast.net
* addons: mirrors.gigenet.com
* extras: holmes.umflint.edu
Setting up Install Process
Parsing package install arguments
Resolving Dependencies
--> Running transaction check
---> Package httpd.i386 0:2.2.3-11.el5_1.centos.3 set to be updated
filelists.xml.gz          100% |=========================| 2.8 MB    00:03
filelists.xml.gz          100% |=========================| 681 kB    00:11
filelists.xml.gz          100% |=========================| 122 kB    00:00
filelists.xml.gz          100% |=========================|  150 B    00:00
--> Finished Dependency Resolution
Dependencies Resolved
=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
httpd                   i386       2.2.3-11.el5_1.centos.3  base              1.1 M
Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)         
Total download size: 1.1 M
Downloading Packages:
(1/1): httpd-2.2.3-11.el5 100% |=========================| 1.1 MB    00:01     
exiting because --downloadonly specified
To see downloaded file, enter:
# ls -l /opt/*.rpm
Sample output:
-rw-r--r-- 1 root root 1116426 Jan 17 03:36 /opt/httpd-2.2.3-11.el5_1.centos.3.i386.rpm
-rw-r--r-- 1 root root   83452 Oct  2  2007 /opt/lighttpd-fastcgi-1.4.18-1.el5.rf.i386.rpm
-rw-r--r-- 1 root root  635045 Oct 20  2007 /opt/psad-2.1-1.i386.rpm
如果某个软件从来没有安装过，现在想通过yum把它下载下来，可以这样：
# yum install perl-MailTools --downloadonly --downloaddir=/opt -y
Loading "installonlyn" plugin
Loading "downloadonly" plugin
Loading "security" plugin
Loading "rhnplugin" plugin
This system is not registered with RHN.
RHN support will be disabled.
Setting up Install Process
Setting up repositories
Reading repository metadata in from local files
Parsing package install arguments
Resolving Dependencies
--> Populating transaction set with selected packages. Please wait.
---> Downloading header for perl-MailTools to pack into transaction set.
perl-MailTools-2.03-1.el5 100% |=========================|  11 kB    00:00
---> Package perl-MailTools.noarch 0:2.03-1.el5.rf set to be updated
--> Running transaction check
Dependencies Resolved
=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
perl-MailTools          noarch     2.03-1.el5.rf    dag               100 k
Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)
Total download size: 100 k
Downloading Packages:
(1/1): perl-MailTools-2.0 100% |=========================| 100 kB    00:02
exiting because --downloadonly specified