今天重置了下虚拟机，yum准备安装gcc编译器，出现如下错误
[root@localhost ~]# yum install -y gcc*
Loaded plugins: fastestmirror, langpacks
Existing lock /var/run/yum.pid: another copy is running as pid 3593.
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: PackageKit
Memory : 109 M RSS (447 MB VSZ)
Started: Thu Jul 26 18:25:02 2018 - 01:38 ago
State : Sleeping, pid: 3593
Another app is currently holding the yum lock; waiting for it to exit...
The other application is: PackageKit
Memory : 109 M RSS (447 MB VSZ)
Started: Thu Jul 26 18:25:02 2018 - 01:40 ago
State : Sleeping, pid: 3593
但是我这是一个新的虚拟机，而且当前就连接了一个ssh用户，也没有使用yum,
显示是yum在锁定状态中Existing lock /var/run/yum.pid，也知道pid是3593 通过kill干掉他
[root@localhost ~]# kill -9 3593
然后再次检查
[root@localhost ~]#** yum repolist **
BDB2053 Freeing read locks for locker 0x9b9: 3593/140359627216704
BDB2053 Freeing read locks for locker 0x9b7: 3593/140359627216704
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* base: mirrors.163.com
* extras: mirrors.163.com
* updates: mirrors.tuna.tsinghua.edu.cn
repo id repo name status
base/7/x86_64 CentOS-7 - Base 9,911
extras/7/x86_64 CentOS-7 - Extras 363
updates/7/x86_64 CentOS-7 - Updates 1,004
repolist: 11,278
这样yum可以正常使用
[root@localhost ~]# yum install -y gcc*
Loaded plugins: fastestmirror, langpacks
Loading mirror speeds from cached hostfile
* base: mirrors.163.com
* extras: mirrors.163.com
* updates: mirrors.tuna.tsinghua.edu.cn
Resolving Dependencies
…………
…………
Installed:
gcc.x86_64 0:4.8.5-28.el7_5.1 gcc-c++.x86_64 0:4.8.5-28.el7_5.1 gcc-gfortran.x86_64 0:4.8.5-28.el7_5.1
gcc-gnat.x86_64 0:4.8.5-28.el7_5.1 gcc-go.x86_64 0:4.8.5-28.el7_5.1 gcc-objc.x86_64 0:4.8.5-28.el7_5.1
gcc-objc++.x86_64 0:4.8.5-28.el7_5.1 gcc-plugin-devel.x86_64 0:4.8.5-28.el7_5.1
Dependency Installed:
cpp.x86_64 0:4.8.5-28.el7_5.1 glibc-devel.x86_64 0:2.17-222.el7 glibc-headers.x86_64 0:2.17-222.el7
gmp-devel.x86_64 1:6.0.0-15.el7 kernel-headers.x86_64 0:3.10.0-862.9.1.el7 libgfortran.x86_64 0:4.8.5-28.el7_5.1
libgnat.x86_64 0:4.8.5-28.el7_5.1 libgnat-devel.x86_64 0:4.8.5-28.el7_5.1 libgo.x86_64 0:4.8.5-28.el7_5.1
libgo-devel.x86_64 0:4.8.5-28.el7_5.1 libmpc.x86_64 0:1.0.1-3.el7 libmpc-devel.x86_64 0:1.0.1-3.el7
libobjc.x86_64 0:4.8.5-28.el7_5.1 libquadmath.x86_64 0:4.8.5-28.el7_5.1 libquadmath-devel.x86_64 0:4.8.5-28.el7_5.1
libstdc++-devel.x86_64 0:4.8.5-28.el7_5.1 mpfr-devel.x86_64 0:3.1.1-4.el7
Dependency Updated:
glibc.x86_64 0:2.17-222.el7 glibc-common.x86_64 0:2.17-222.el7 libgcc.x86_64 0:4.8.5-28.el7_5.1 libgomp.x86_64 0:4.8.5-28.el7_5.1
libstdc++.x86_64 0:4.8.5-28.el7_5.1
Complete!
**总结：执行命令中遇到问题基本思路：
首先一定学会分析问题，必须有一个清晰的思路。
首先遇到问题不能害怕，
其次不建议直接去上网搜索，搜了好多，很可能还没解决。
再此分享下我的解决思路，如下三步。希望对大家有帮助，当然我也是在不断地学习中。
看提示（终端显示的错误信息，建议执行方法）
查日志（查看系统日志 /var/log/目录下的日志文件，如果是相关服务，请查看服务的日志文件，比如MySQL数据库的日志文件等）
上谷歌（通过网络查看是否有相同或者相似的问题）**
