解決 yum 安裝軟體時提示被鎖定

有時用yum升級一些檔案時，會出現以下情況：
Existing lock /var/run/yum.pid: another copy is running as pid 3046.
Another app is currently holding the yum lock; waiting for it to exit...
Another app is currently holding the yum lock; waiting for it to exit...
Another app is currently holding the yum lock; waiting for it to exit...
Another app is currently holding the yum lock; waiting for it to exit...
Another app is currently holding the yum lock; waiting for it to exit...
可以通過強制關掉yum進程：

rm -f /var/run/yum.pidservice yum-updatesd restart

然後就可以使用yum了。