以下情况的处理：
[root@localhost ~]# yum repolist
Loaded plugins: fastestmirror, langpacks
Existing lock /var/run/yum.pid: another copy is running as pid 2729.
Another app is currently holding the yum lock; waiting for it to exit…
The other application is: PackageKit
Memory : 47 M RSS (463 MB VSZ)
Started: Fri Dec 8 17:04:27 2023 - 00:23 ago
State : Sleeping, pid: 2729

[root@localhost ~]#kill -9 2729
[root@localhost ~]#yum clean all
[root@localhost ~]#yum repolist

装yum源
rm -rf /etc/yum.repos.d/*
wget -O /etc/yum.repos.d/CentOS-Base.repo http://mirrors.aliyun.com/repo/Centos-7.repo
yum repolist
装apache
yum -y install httpd
rpm -q httpd
rpm -qc httpd
ls /etc/httpd/
vim /etc/httpd/conf/httpd.conf
history

域名解析：
vim /etc/hosts 负责本地解析
vim /etc/resolv.conf DNS服务器的配置优先级低于hosts

[root@localhost ~]# vim /etc/httpd/conf/httpd.conf
echo i love me > /var/www/html/index.html
[root@localhost ~]# systemctl status httpd
[root@localhost ~]# systemctl stop firewalld.service关闭防火墙