Introduction

验证网卡的PXE功能，需要搭建PXE server，PXE是网卡从服务器端启动，然后下载系统镜像，从来实现远程系统启动或者系统安装到本地。

PXE Server组件

DHCP Server
负责给PXE网卡分配网络IP地址，并通过网络提供指定的系统启动文件。
TFTP Server
PXE网卡通过TFTP协议获取启动文件，例如：pxelinux.0，vmlinuz，initrd.img, undionly.kpxe等。
FTP Server
PXE网卡通过FTP协议下载系统镜像文件，包含一个完整的系统。
Syslinux
是一个启动加载器集合，可以从硬盘、光盘或通过 PXE 的网络引导启动系统。
iPXE
iPXE is the leading open source network boot firmware. It provides a full PXE implementation enhanced with additional features such as:

• boot from a web server via HTTP
• boot from an iSCSI SAN
• boot from a Fibre Channel SAN via FCoE
• boot from an AoE SAN
• boot from a wireless network
• boot from a wide-area network
• boot from an Infiniband network
• control the boot process with a script

下面以 Ubuntu 20.04 为例来示例如何搭建一个自用的PXE Server的过程。

Configure Static IP Address

选定一个网卡作为接下来DHCP Server的外接端口，此处选定网卡 enp1s0 配置静态IP 192.168.10.10。

root@pxe-server:/home/pxe/Desktop# cat /etc/netplan/01-network-manager-all.yaml 
# Let NetworkManager manage all devices on this system
network:
 # version: 2
 # renderer: NetworkManager
  ethernets:
    enp1s0:
      dhcp4: no
      dhcp6: no
      addresses: [192.168.10.10/24]
      gateway4: 192.168.10.1
      nameservers:
        addresses: [114.114.114.114]

root@pxe-server:/home/pxe/Desktop# ifconfig
enp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.10.10  netmask 255.255.255.0  broadcast 192.168.10.255
        ether xx:xx:xx:xx:xx:xx  txqueuelen 1000  (Ethernet)

也可以通过ifconfig的方法来配置临时IP，系统重启需要重新配置。有时发现重新开机后，之前配置的静态IP没有成功，那就手动配置一次，然后重新启动DHCP Server即可。

root@pxe-server:/home/pxe/Desktop# ifconfig enp1s0 192.168.10.10

Configure DHCP Service

1. 安装DHCP Server

root@pxe-server:/home/pxe/Desktop# apt install isc-dhcp-server

2. 编辑/etc/default/isc-dhcp-server
   此处选择DHCP Server要绑定的网卡 enp1s0.

root@pxe-server:/home/pxe/Desktop# cat /etc/default/isc-dhcp-server
# Defaults for isc-dhcp-server (sourced by /etc/init.d/isc-dhcp-server)

# Path to dhcpd's config file (default: /etc/dhcp/dhcpd.conf).
#DHCPDv4_CONF=/etc/dhcp/dhcpd.conf
#DHCPDv6_CONF=/etc/dhcp/dhcpd6.conf

# Path to dhcpd's PID file (default: /var/run/dhcpd.pid).
#DHCPDv4_PID=/var/run/dhcpd.pid
#DHCPDv6_PID=/var/run/dhcpd6.pid

# Additional options to start dhcpd with.
#	Don't use options -cf or -pf here; use DHCPD_CONF/ DHCPD_PID instead
#OPTIONS=""

# On what interfaces should the DHCP server (dhcpd) serve DHCP requests?
#	Separate multiple interfaces with spaces, e.g. "eth0 eth1".
#INTERFACESv4=""
#INTERFACESv6=""
INTERFACES="enp1s0" #可以用这个参数设置，避免后续报出Error/warning.

3. 编辑/etc/dhcp/dhcpd.conf
   此处配置DHCP Server的关键信息，包括IP地址段，路由，针对PXE Server，还需要包括pxe启动image, next-server.

root@pxe-server:/home/pxe/Desktop# cat /etc/dhcp/dhcpd.conf
# dhcpd.conf
#
# Sample configuration file for ISC dhcpd
#
# Attention: If /etc/ltsp/dhcpd.conf exists, that will be used as
# configuration file instead of this file.
#

# option definitions common to all supported networks...
option domain-name "example.org";
#option domain-name-servers ns1.example.org, ns2.example.org;#这行注释掉，有时导致DHCP client获取IP失败

default-lease-time 600;
max-lease-time 7200;

# The ddns-updates-style parameter controls whether or not the server will
# attempt to do a DNS update when a lease is confirmed. We default to the
# behavior of the version 2 packages ('none', since DHCP v2 didn't
# have support for DDNS.)
ddns-update-style none;

# If this DHCP server is the official DHCP server for the local
# network, the authoritative directive should be uncommented.
#authoritative;

# Use this to send dhcp log messages to a different log file (you also
# have to hack syslog.conf to complete the redirection).
#log-facility local7;

# No service will be given on this subnet, but declaring it helps the 
# DHCP server to understand the network topology.

#subnet 10.152.187.0 netmask 255.255.255.0 {
#}

# This is a very basic subnet declaration.

#subnet 10.254.239.0 netmask 255.255.255.224 {
#  range 10.254.239.10 10.254.239.20;
#  option routers rtr-239-0-1.example.org, rtr-239-0-2.example.org;
#}

# This declaration allows BOOTP clients to get dynamic addresses,
# which we don't really recommend.

#subnet 10.254.239.32 netmask 255.255.255.224 {
#  range dynamic-bootp 10.254.239.40 10.254.239.60;
#  option broadcast-address 10.254.239.31;
#  option routers rtr-239-32-1.example.org;
#}

# A slightly different configuration for an internal subnet.
#subnet 10.5.5.0 netmask 255.255.255.224 {
#  range 10.5.5.26 10.5.5.30;
#  option domain-name-servers ns1.internal.example.org;
#  option domain-name "internal.example.org";
#  option subnet-mask 255.255.255.224;
#  option routers 10.5.5.1;
#  option broadcast-address 10.5.5.31;
#  default-lease-time 600;
#  max-lease-time 7200;
#}
option client-architecture code 93 = unsigned integer 16;
subnet 192.168.10.0 netmask 255.255.255.0 {
  range 192.168.10.11 192.168.10.30;
#  option domain-name-servers 192.168.10.2, 192.168.10.3;
#  option domain-name "internal.example.org";
#  option subnet-mask 255.255.255.0;
  option routers 192.168.10.1;
#  option broadcast-address 192.168.10.2;
#  default-lease-time 600;
#  max-lease-time 7200;
  # tftp server IP Address
  next-server 192.168.10.10;
  
  # ++++++++++++++++++++++++ For PXE Boot file
  #filename "pxelinux.0";
  # ------------------------ For PXE Boot file
  
  # ++++++++++++++++++++++++ For iPXE Boot files
  if exists user-class and option user-class = "iPXE" {
      filename "ipxe.script";   # for iPXE booting scripts
  } elsif option client-architecture = 00:00 {
      filename "undionly.kpxe"; # for booting legacy PXE
  } else {
      filename "ipxe.efi";      # for booting UFEI PXE
  }
  # ------------------------ For iPXE Boot files
}


# Hosts which require special configuration options can be listed in
# host statements.   If no address is specified, the address will be
# allocated dynamically (if possible), but the host-specific information
# will still come from the host declaration.

#host passacaglia {
#  hardware ethernet 0:0:c0:5d:bd:95;
#  filename "vmunix.passacaglia";
#  server-name "toccata.example.com";
#}

# Fixed IP addresses can also be specified for hosts.   These addresses
# should not also be listed as being available for dynamic assignment.
# Hosts for which fixed IP addresses have been specified can boot using
# BOOTP or DHCP.   Hosts for which no fixed address is specified can only
# be booted with DHCP, unless there is an address range on the subnet
# to which a BOOTP client is connected which has the dynamic-bootp flag
# set.
#host fantasia {
#  hardware ethernet 08:00:07:26:c0:a5;
#  fixed-address fantasia.example.com;
#}

# You can declare a class of clients and then do address allocation
# based on that.   The example below shows a case where all clients
# in a certain class get addresses on the 10.17.224/24 subnet, and all
# other clients get addresses on the 10.0.29/24 subnet.

#class "foo" {
#  match if substring (option vendor-class-identifier, 0, 4) = "SUNW";
#}

#shared-network 224-29 {
#  subnet 10.17.224.0 netmask 255.255.255.0 {
#    option routers rtr-224.example.org;
#  }
#  subnet 10.0.29.0 netmask 255.255.255.0 {
#    option routers rtr-29.example.org;
#  }
#  pool {
#    allow members of "foo";
#    range 10.17.224.10 10.17.224.250;
#  }
#  pool {
#    deny members of "foo";
#    range 10.0.29.10 10.0.29.230;
#  }
#}

4. Enable DHCP service
   配置完成后，重启DHCP service，之后如果发现DHCP不工作的时候，都可以通过这种方式重启来修正。

root@pxe-server:/home/pxe/Desktop# service isc-dhcp-server restart
root@pxe-server:/home/pxe/Desktop# service isc-dhcp-server status
● isc-dhcp-server.service - ISC DHCP IPv4 server
     Loaded: loaded (/lib/systemd/system/isc-dhcp-server.service; enabled; vendor preset: enabled)
     Active: active (running) since Thu 2021-04-22 17:16:17 CST; 1s ago
       Docs: man:dhcpd(8)
   Main PID: 2827 (dhcpd)
      Tasks: 4 (limit: 8778)
     Memory: 4.8M
     CGroup: /system.slice/isc-dhcp-server.service
             └─2827 dhcpd -user dhcpd -group dhcpd -f -4 -pf /run/dhcp-server/dhcpd.pid -cf /etc/dhcp/dhcpd.conf enp1s0

4月 22 17:16:17 pxe-server sh[2827]: Wrote 1 leases to leases file.
4月 22 17:16:17 pxe-server dhcpd[2827]: Listening on LPF/enp1s0/xx:xx:xx:xx:xx:xx/192.168.10.0/24
4月 22 17:16:17 pxe-server sh[2827]: Listening on LPF/enp1s0/xx:xx:xx:xx:xx:xx/192.168.10.0/24
4月 22 17:16:17 pxe-server sh[2827]: Sending on   LPF/enp1s0/xx:xx:xx:xx:xx:xx/192.168.10.0/24
4月 22 17:16:17 pxe-server sh[2827]: Sending on   Socket/fallback/fallback-net
4月 22 17:16:17 pxe-server dhcpd[2827]: Sending on   LPF/enp1s0/xx:xx:xx:xx:xx:xx/192.168.10.0/24
4月 22 17:16:17 pxe-server dhcpd[2827]: Sending on   Socket/fallback/fallback-net
4月 22 17:16:17 pxe-server dhcpd[2827]: Server starting service.
4月 22 17:16:18 pxe-server dhcpd[2827]: reuse_lease: lease age 118 (secs) under 25% threshold, reply with unaltered, existing lease for 192.168.10.11
4月 22 17:16:18 pxe-server dhcpd[2827]: DHCPREQUEST for 192.168.10.11 from xx:xx:xx:xx:xx:xx ( ) via enp1s0

Configure TFTP Service

1. 安装TFTP服务

root@pxe-server:/home/pxe/Desktop# apt install tftpd-hpa

2. 配置/etc/default/tftpd-hpa

root@pxe-server:/home/pxe/Desktop# cat /etc/default/tftpd-hpa
# /etc/default/tftpd-hpa

TFTP_USERNAME="tftp"
TFTP_DIRECTORY="/srv/tftp" #下载文件目录
TFTP_ADDRESS=":69"
TFTP_OPTIONS="--secure"

3. Enable TFTP service

root@pxe-server:/home/pxe/Desktop# service tftpd-hpa restart
root@pxe-server:/home/pxe/Desktop# service tftpd-hpa status
● tftpd-hpa.service - LSB: HPAs tftp server
     Loaded: loaded (/etc/init.d/tftpd-hpa; generated)
     Active: active (running) since Thu 2021-04-22 17:44:09 CST; 1s ago
       Docs: man:systemd-sysv-generator(8)
    Process: 1817 ExecStart=/etc/init.d/tftpd-hpa start (code=exited, status=0/SUCCESS)
      Tasks: 1 (limit: 8778)
     Memory: 1.0M
     CGroup: /system.slice/tftpd-hpa.service
             └─1825 /usr/sbin/in.tftpd --listen --user tftp --address :69 --secure /srv/tftp

4月 22 17:44:09 pxe-server systemd[1]: Starting LSB: HPAs tftp server...
4月 22 17:44:09 pxe-server tftpd-hpa[1817]:  * Starting HPAs tftpd in.tftpd
4月 22 17:44:09 pxe-server tftpd-hpa[1817]:    ...done.
4月 22 17:44:09 pxe-server systemd[1]: Started LSB: HPA's tftp server.

PXE验证

Configure FTP Service

用来下载系统安装镜像的服务有几种选项，FTP，HTTP，NFS等，此处选择FTP.

1. 安装 FTP Server

root@pxe-server:/home/pxe/Desktop# apt install vsftpd

FTP的默认文件夹为"/srv/ftp/"，需要把OS Image copy到这个目录，以下为redhat8.1的OS images.

root@pxe-server:/home/pxe/Desktop# ls /srv/
ftp  tftp
root@pxe-server:/home/pxe/Desktop# ls /srv/ftp/
AppStream  EFI   extra_files.json  images    media.repo               RPM-GPG-KEY-redhat-release
BaseOS     EULA  GPL               isolinux  RPM-GPG-KEY-redhat-beta  TRANS.TBL

2. 配置/etc/vsftpd.conf

3. Enable FTP service

root@pxe-server:/home/pxe/Desktop#service vsftpd status
● vsftpd.service - vsftpd FTP server
     Loaded: loaded (/lib/systemd/system/vsftpd.service; enabled; vendor preset: enabled)
     Active: active (running) since Tue 2021-04-13 05:36:40 CST; 12h ago
   Main PID: 32304 (vsftpd)
      Tasks: 1 (limit: 154342)
     Memory: 21.5M
     CGroup: /system.slice/vsftpd.service
             └─32304 /usr/sbin/vsftpd /etc/vsftpd.conf

4 13 05:36:40 pxeserver systemd[1]: Starting vsftpd FTP server...
4 13 05:36:40 pxeserver systemd[1]: Started vsftpd FTP server.

Configure Syslinux for PXE verification

如果不需要验证PXE，这一章节的操作可以略过，直接到下一章节，可以配置iPXE。

1. install Syslinux

root@pxe-server:/home/pxe/Desktop# apt install syslinux

安装完成后，可以从下列目录中找到legacy/uefi启动image

root@pxe-server:/home/pxe/Desktop# ls /usr/lib/syslinux
mbr  memdisk  modules
root@pxe-server:/home/pxe/Desktop# ls /usr/lib/syslinux/modules
bios  efi32  efi6

2. Copy pxelinux.0文件到"/srv/tftp/“目录，此处应该包含所有用到的boot image,包括iPXE的，这几个文件名字都包含在”/etc/dhcp/dhcpd.conf".

3. 从OS image文件中copy initrd.img,vmlinuz到tftp/pxeboot/目录中

root@pxe-server:/home/pxe/Desktop# ls /srv/ftp/images/pxeboot/ #redhat8.1的OS images
initrd.img  vmlinuz
root@pxe-server:/home/pxe/Desktop# ls /srv/tftp/pxeboot/
initrd.img  vmlinuz

4. 配置pxelinux.cfg/default文件

root@pxe-server:/home/pxe/Desktop# cat /srv/tftp/pxelinux.cfg/default
default redhat81
timeout 3
prompt 0
label redhat81
menu title redhat 8.1 pxe installtion
kernel /pxeboot/vmlinuz
append initrd=/pxeboot/initrd.img inst.stage2=ftp://192.168.10.10/

此时，legacy PXE的配置完成，可以用来验证PXE的功能了。

iPXE验证

Install HTTP Server

iPXE默认不是support FTP server，需要安装HTTP Server来完成安装文件的传输，安装过程十分简单。

root@pxe-server:/home/pxe/Desktop# apt install apache2
root@pxe-server:/home/pxe/Desktop# service apache2 status

安装完成后，把安装文件copy到/var/www/html目录，把默认的index.html删除即可。

root@pxe-server:/home/pxe/Desktop# ls /var/www/html
RHEL8.3

iPXE verification

此处用来配置iPXE，iPXE可以同时support legacy and uefi PXE。

root@pxe-server:/home/pxe/Desktop# apt install ipxe
root@pxe-server:/home/pxe/Desktop# cp /usr/lib/ipxe/{ipxe.efi,undionly.kpxe} /srv/tftp/ 
root@pxe-server:/home/pxe/Desktop# ls /srv/tftp/ 
ipxe.efi undionly.kpxe ipxe.script

针对ipxe.script，此处给出一个示例：

#!ipxe

:start
menu iPXE Boot Options
item shell iPXE shell
item linux-net Linux OS installation
item exit  Exit to BIOS
choose --default linux-net --timeout 10000 option && goto ${option}
:shell
shell
:linux-net
set server_root http://192.168.10.10/
initrd ${server_root}/RHEL8.3/images/pxeboot/initrd.img
kernel ${server_root}/RHEL8.3/images/pxeboot/vmlinuz inst.repo=${server_root}/RHEL8.3/ initrd=initrd.img
boot
:exit
exit