PXE(preboot execute environment,预启动执行环境)是由Intel公司开发的最新技术，工作于Client/Server的网络模式，支持工作站通过网络从远端服务器下载映像，并由此支持通过网络启动操作系统，在启动过程中，终端要求服务器分配IP地址，再用TFTP（trivial file transfer protocol）或MTFTP(multicast trivial file transfer protocol)协议下载一个启动软件包到本机内存中执行，由这个启动软件包完成终端基本软件设置，从而引导预先安装在服务器中的终端操作系统。PXE可以引导多种操作系统，如：Windows95/98/2000/windows2003/windows2008/win7/win8,linux等。
# 为了后续配置方便，首先关闭系统SELinux和防火墙
# 关闭SELinux，修改文件使SELINUX=disabled
[root@pxe1 ~]# vim /etc/selinux/config
# This file controls the state of SELinux on the system.
# SELINUX= can take one of these three values:
# enforcing - SELinux security policy is enforced.
# permissive - SELinux prints warnings instead of enforcing.
# disabled - No SELinux policy is loaded.
SELINUX=disabled
# SELINUXTYPE= can take one of three two values:
# targeted - Targeted processes are protected,
# minimum - Modification of targeted policy. Only selected processes are protected.
# mls - Multi Level Security protection.
SELINUXTYPE=targeted
#重启系统后配置生效，查看SELinux的状态。
[root@pxe1 ~]# sestatus
SELinux status: disabled
#关闭防火墙
[root@pxe1 ~]# systemctl stop firewalld
[root@pxe1 ~]# systemctl disable firewalld
[root@pxe1 ~]# systemctl status firewalld
● firewalld.service - firewalld - dynamic firewall daemon
Loaded: loaded (/usr/lib/systemd/system/firewalld.service; disabled; vendor preset: enabled)
Active: inactive (dead)
Docs: man:firewalld(1)
[root@pxe1 yum.repos.d]# cat /etc/dhcp/dhcpd.conf
#
# DHCP Server Configuration file.
# see /usr/share/doc/dhcp*/dhcpd.conf.example
# see dhcpd.conf(5) man page
subnet 192.168.56.0 netmask 255.255.255.0 {
range 192.168.56.10 192.168.56.20;
filename "pxelinux.0";
next-server 192.168.56.14;
}
# subnet 192.168.56.0 netmask 255.255.255.0 服务端IP网段及掩码
# range 192.168.56.10 192.168.56.20; dhcp分发的地址范围，最好将本机IP包含在内。
# filename "pxelinux.0"; 指定引导文件位置，这里是TFTP根目录下的pxelinux.0。
# next-server 192.168.56.14; TFTP服务器地址。
3.3 启动dhcp服务
[root@pxe1 yum.repos.d]# systemctl restart dhcpd
[root@pxe1 yum.repos.d]# systemctl enable dhcpd
Created symlink from /etc/systemd/system/multi-user.target.wants/dhcpd.service to /usr/lib/systemd/system/dhcpd.service.
[root@pxe1 yum.repos.d]# systemctl status dhcpd
● dhcpd.service - DHCPv4 Server Daemon
Loaded: loaded (/usr/lib/systemd/system/dhcpd.service; enabled; vendor preset: disabled)
Active: active (running) since Thu 2017-05-25 11:00:26 CST; 26s ago
Docs: man:dhcpd(8)
man:dhcpd.conf(5)
Main PID: 11849 (dhcpd)
Status: "Dispatching packets..."
CGroup: /system.slice/dhcpd.service
└─11849 /usr/sbin/dhcpd -f -cf /etc/dhcp/dhcpd.conf -user dhcpd -group dhcpd --no-pid
May 25 11:00:26 pxe1 dhcpd[11849]: No subnet declaration for virbr0 (192.168.122.1).
May 25 11:00:26 pxe1 dhcpd[11849]: ** Ignoring requests on virbr0. If this is not what
May 25 11:00:26 pxe1 dhcpd[11849]: you want, please write a subnet declaration
May 25 11:00:26 pxe1 dhcpd[11849]: in your dhcpd.conf file for the network segment
May 25 11:00:26 pxe1 dhcpd[11849]: to which interface virbr0 is attached. **
May 25 11:00:26 pxe1 dhcpd[11849]:
May 25 11:00:26 pxe1 dhcpd[11849]: Listening on LPF/enp0s3/08:00:27:43:c1:1d/192.168.56.0/24
May 25 11:00:26 pxe1 dhcpd[11849]: Sending on LPF/enp0s3/08:00:27:43:c1:1d/192.168.56.0/24
May 25 11:00:26 pxe1 dhcpd[11849]: Sending on Socket/fallback/fallback-net
May 25 11:00:26 pxe1 systemd[1]: Started DHCPv4 Server Daemon.
[root@pxe1 yum.repos.d]# netstat -nulp | grep dhcp
udp 0 0 0.0.0.0:67 0.0.0.0:* 11849/dhcpd
udp 0 0 0.0.0.0:16465 0.0.0.0:* 11849/dhcpd
udp6 0 0 :::31651 :::* 11849/dhcpd
[root@pxe1 kk]# ls /var/ftp/
ks.cfg pub
[root@pxe1 kk]# ftp 192.168.56.14
Connected to 192.168.56.14 (192.168.56.14).
220 (vsFTPd 3.0.2)
Name (192.168.56.14:root): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls
227 Entering Passive Mode (192,168,56,14,217,98).
150 Here comes the directory listing.
-rw-r--r-- 1 0 0 1459 May 25 09:36 ks.cfg
drwxr-xr-x 8 0 0 2048 Dec 05 13:20 pub
226 Directory send OK.
ftp> get ks.cfg
local: ks.cfg remote: ks.cfg
227 Entering Passive Mode (192,168,56,14,152,101).
150 Opening BINARY mode data connection for ks.cfg (1459 bytes).
226 Transfer complete.
1459 bytes received in 0.0433 secs (33.68 Kbytes/sec)
ftp> bye
221 Goodbye.
[root@pxe1 kk]# ls
ks.cfg
label linux
menu label ^Install CentOS Linux 7 by kickstart
menu default
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.ks=ftp://192.168.56.14/ks.cfg
label linux 2
menu label ^Install CentOS Linux 7 by vnc
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.vnc inst.vncpassword=password
label linux 3
menu label ^Install CentOS Linux 7 by vnc -listen
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.vnc inst.vncconnect=192.168.56.1
在系统启动过程中，菜单依次对应如下内容：
8.1 kickstart菜单介绍
菜单一介绍：
label linux
menu label ^Install CentOS Linux 7 by kickstart
menu default
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.ks=ftp://192.168.56.14/ks.cfg
# 使用kickstart自动安装
# 这项菜单表示镜像文件在FTP根目录/var/ftp/pub下，kickstart文件在FTP根目录/var/ftp下。
菜单二介绍：
label linux 2
menu label ^Install CentOS Linux 7 by vnc
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.vnc inst.vncpassword=password
# 使用vnc手动安装
# 该菜单表示镜像文件在FTP根目录/var/ftp/pub下，vnc密码为password，选中该菜单后，系统启动后会提示vnc登录的IP及端口，vnc连接后，便可进行手动系统安装，也可以在菜单最后指定kickstart文件位置，自动安装。
如图：
菜单三介绍：
label linux 3
menu label ^Install CentOS Linux 7 by vnc -listen
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.vnc inst.vncconnect=192.168.56.1
# 该菜单项表示使用vnc监听模式进行系统安装
# 该菜单表示镜像文件在FTP根目录/var/ftp/pub下，vnc监听进程在计算机192.168.56.1上，无登录密码；
# 注意：inst.vncconnect=192.168.56.1 指的是将要运行vnc客户端的计算机IP地址。
[root@pxe1 tftpboot]# ls /var/lib/tftpboot/
initrd.img menu.c32 pxelinux.0 pxelinux.cfg vmlinuz
菜单文件内容为：
[root@pxe1 tftpboot]# cat /var/lib/tftpboot/pxelinux.cfg/default
default menu.c32
timeout 60
menu title CentOS 7 Pxe Menu
label linux
menu label ^Install CentOS Linux 7 by kickstart
menu default
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.ks=ftp://192.168.56.14/ks.cfg
label linux 2
menu label ^Install CentOS Linux 7 by vnc
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.vnc inst.vncpassword=password
label linux 3
menu label ^Install CentOS Linux 7 by vnc -listen
kernel vmlinuz
append initrd=initrd.img inst.repo=ftp://192.168.56.14/pub inst.vnc inst.vncconnect=192.168.56.1
