PXE 启动 archlinux

本文没有编写完成，以后也许不会更新。

最近想整个 PXE 启动的 archlinux 环境，启动之后像 archiso 一样，跑在内存里面。

实现思路

PXE 启动 grub, 然后走 http 下载 kernel 和 initramfs, 在 initramfs 启动过程中下载 rootfs，最后 switch_root 到 rootfs。

搭建一个 tftp、dhcp、http server

根据 archwiki 的指导，我们用 dnsmasq 作为 tftp 与 dhcp server. 下面是我的 dnsmasq 配置(与软件包内置版本的 diff)

diff --git a/dnsmasq.conf b/dnsmasq.conf
index 936e468..07aa658 100644
--- a/dnsmasq.conf
+++ b/dnsmasq.conf
@@ -7,7 +7,7 @@
 # Listen on this specific port instead of the standard DNS port
 # (53). Setting this to zero completely disables DNS function,
 # leaving only DHCP and/or TFTP.
-#port=5353
+port=0

 # The following two options make you a better netizen, since they
 # tell dnsmasq to filter out queries which the public DNS cannot
@@ -113,7 +113,9 @@
 # specified interfaces (and the loopback) give the name of the
 # interface (eg eth0) here.
 # Repeat the line for more than one interface.
-#interface=
+interface=wlp3s0
+interface=virbr0
+interface=br0
 # Or you can specify which interface _not_ to listen on
 #except-interface=
 # Or which to listen on by address (remember to include 127.0.0.1 if
@@ -164,8 +166,9 @@
 # a lease time. If you have more than one network, you will need to
 # repeat this for each network on which you want to supply DHCP
 # service.
-#dhcp-range=192.168.0.50,192.168.0.150,12h
-
+dhcp-range=192.168.122.50,192.168.122.150,12h
+dhcp-range=192.168.2.1,proxy
+dhcp-range=10.42.0.50,10.42.0.240,12h
 # This is an example of a DHCP range where the netmask is given. This
 # is needed for networks we reach the dnsmasq DHCP server via a relay
 # agent. If you don't know what a DHCP relay agent is, you probably
@@ -439,9 +442,9 @@
 # Magic number - needed before anything else is recognised
 #dhcp-option-force=208,f1:00:74:7e
 # Configuration file name
-#dhcp-option-force=209,configs/common
+dhcp-option-force=209,archiso_pxe.cfg
 # Path prefix
-#dhcp-option-force=210,/tftpboot/pxelinux/files/
+dhcp-option-force=210,
 # Reboot time. (Note 'i' to send 32-bit value)
 #dhcp-option-force=211,30i

@@ -449,7 +452,7 @@
 # this if you want to boot machines over the network and you will need
 # a TFTP server; either dnsmasq's built-in TFTP server or an
 # external one. (See below for how to enable the TFTP server.)
-#dhcp-boot=pxelinux.0
+dhcp-boot=/boot/syslinux/ipxe.pxe

 # The same as above, but use custom tftp-server instead machine running dnsmasq
 #dhcp-boot=pxelinux,server.name,192.168.1.100
@@ -458,8 +461,8 @@
 # filenames, the first loads iPXE, and the second tells iPXE what to
 # load. The dhcp-match sets the ipxe tag for requests from iPXE.
 #dhcp-boot=undionly.kpxe
-#dhcp-match=set:ipxe,175 # iPXE sends a 175 option.
-#dhcp-boot=tag:ipxe,http://boot.ipxe.org/demo/boot.php
+dhcp-match=set:ipxe,175 # iPXE sends a 175 option.
+dhcp-boot=tag:ipxe,/boot/syslinux/lpxelinux.0

 # Encapsulated options for iPXE. All the options are
 # encapsulated within option 175
@@ -506,10 +509,10 @@


 # Enable dnsmasq's built-in TFTP server
-#enable-tftp
+enable-tftp

 # Set the root directory for files available via FTP.
-#tftp-root=/var/ftpd
+tftp-root=/tmp/pxe/archiso

 # Do not abort if the tftp-root is unavailable
 #tftp-no-fail
@@ -671,7 +674,7 @@
 #log-queries

 # Log lots of extra information about DHCP transactions.
-#log-dhcp
+log-dhcp

 # Include another lot of configuration options.
 #conf-file=/etc/dnsmasq.more.conf

工作目录为 /tmp/pxe，下面是目录结构 archiso 目录是 archlinux-2023.12.01-x86_64.iso 解压后的文件夹

/tmp/pxe
├── archiso
│   ├── arch
│   ├── boot
│   ├── EFI
│   ├── shellia32.efi
│   └── shellx64.efi
├── archlinux-2023.12.01-x86_64.iso
└── dnsmasq.conf

dnsmasq 启动命令为 (-d 是为了看输出)

sudo dnsmasq -C dnsmasq.conf -d

http server 的启动命令为

sudo darkhttpd /tmp/pxe/archiso --port 80

然后我们从 qemu 建立一个虚拟机，走 pxe 启动，就能进入 livecd 了。

qemu 启动命令

sudo qemu-system-x86_64 -boot n -netdev tap,id=mynet0,ifname=tap0,script=no,downscript=no -device e1000,netdev=mynet0,mac=52:55:00:d1:55:01 -nographic -curses

自定义 initramfs

find . 2>/dev/null | cpio -o  -R root:root -H newc | xz -3 --format=lzma > ../initramfs-linux.img

自定义 rootfs

pacstrap -K NEWROOT base base-devel

然后打包成 squashfs

sudo mksquashfs . ../airootfs.sfs \
  -not-reproducible \
  -xattrs \
  -wildcards \
  -noappend \
  -progress \
  -mem 5G \
  -e \
    var/cache/pacman/pkg \
    var/lib/pacman/sync \
    var/log/journal \
    efi \
    boot/grub \
    boot/initramfs-linux"*".img \
    boot/vmlinuz-linux

qemu 调试

qemu-system-x86_64 \
-m 8G \
-chardev stdio,id=char0,logfile=serial.log,signal=off \
-serial chardev:char0 \
-vga virtio \
-net nic -net user \
-device nec-usb-xhci,id=xhci,addr=0x1b \
-device usb-tablet,id=tablet,bus=xhci.0,port=1 \
-device usb-kbd,id=keyboard,bus=xhci.0,port=2 \
-smp 4,cores=4  -kernel vmlinuz-linux  -initrd initramfs-linux.img -append 'ip=:::::eth0:dhcp'

参考资料

1. Preboot Execution Environment
2. PXE network boot methods