[root@localhost network-scripts]# yum install vim
Loaded plugins: fastestmirror
Existing lock /var/run/yum.pid: another copy is running as pid 2503.
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:00 ago
State : Traced/Stopped, pid: 2503
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:02 ago
State : Traced/Stopped, pid: 2503
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:04 ago
State : Traced/Stopped, pid: 2503
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:06 ago
State : Traced/Stopped, pid: 2503
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:08 ago
State : Traced/Stopped, pid: 2503
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:10 ago
State : Traced/Stopped, pid: 2503
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: yum
Memory : 19 M RSS (306 MB VSZ)
Started: Thu Oct 29 23:03:02 2015 - 04:12 ago
State : Traced/Stopped, pid: 2503
解决办法：
rm -rf /var/run/yum.pid 来强行解除锁定，然后就可以正常使用你的yum了