1.PEX——自动化安装操作系统

1.1原理

PXE 启动时，客户端先找 DHCP 服务器要 IP 和 PXE 文件位置，再从 TFTP 服务器获取pxelinux.0并执行，接着获取配置文件pxelinux.cfg并读取。之后获取 Linux 内核文件vmlinuz和初始化镜像文件initrd.img，最后启动 Linux 内核

1.2实现PXE自动化安装CentOS6、7、8

1.2.1 安装前准

关闭PXE服务端的防火墙和 selinux，设置静态获取地址，关闭Vmware软件中的DHCP服务，基于NAT模式.

6.3.2 安装所需软件并启动服务

[root@Rocky8 ~]# yum install -y tree dhcp-server tftp-server httpd syslinux-nonlinux vim

[root@Rocky8 ~]# systemctl enable --now httpd tftp.socket
Created symlink /etc/systemd/system/multi-user.target.wants/httpd.service → /usr/lib/systemd/system/httpd.service.

1.2.2配置DHCP服务

[root@Rocky8 ~]# vim /etc/dhcp/dhcpd.conf
option domain-name "baidu.com";
option domain-name-servers 233.5.5.5,114.114.114.114;
default-lease-time 86400;
max-lease-time 106400;
log-facility local7;
subnet 10.0.0.0 netmask 255.255.255.0 {
  range 10.0.0.100 10.0.0.200;
  option routers 10.0.0.1;
  next-server 10.0.0.9;
  filename "pxelinux.0";
}

[root@Rocky8 ~]# systemctl enable --now dhcpd
Created symlink /etc/systemd/system/multi-user.target.wants/dhcpd.service → /usr/lib/systemd/system/dhcpd.service.

1.2.3准备安装系统yum仓库

[root@Rocky8 ~]# mkdir -pv /var/www/html/centos{6,7,8}
mkdir: 已创建目录 '/var/www/html/centos6'
mkdir: 已创建目录 '/var/www/html/centos7'
mkdir: 已创建目录 '/var/www/html/centos8'

[root@Rocky8 ~]# mkdir /var/www/html/ks
[root@Rocky8 ~]# init 0

[root@Rocky8 ~]# echo "- - -">>/sys/class/scsi_host/host0/scan
[root@Rocky8 ~]# echo "- - -">>/sys/class/scsi_host/host1/scan
[root@Rocky8 ~]# echo "- - -">>/sys/class/scsi_host/host2/scan      --可以不用
[root@Rocky8 ~]# mount /dev/sr0 /var/www/html/centos8/
[root@Rocky8 ~]# mount /dev/sr2 /var/www/html/centos7
[root@Rocky8 ~]# mount /dev/sr1 /var/www/html/centos6
[root@Rocky8 ~]# df -h | grep ^/dev/sr*
/dev/sr0              11G   11G     0  100% /var/www/html/centos8
/dev/sr2             4.4G  4.4G     0  100% /var/www/html/centos7
/dev/sr1             3.8G  3.8G     0  100% /var/www/html/centos6