Build a customized iPXE firmware and deploy a chain loading environment

As the number of devices in my network has increased, so has the workload of performing maintenance on these systems. From time to time I need to use some rescue systems, such as WinPE and Linux LiveCD. Mounting boot images for them often requires the use of a corresponding management tool or out-of-band management, such as IPMI or BMC manager. The physical machine even needs to burn a USB boot disk.

Preboot eXecution Environment, the abbreviation is PXE, provides a mechanism for booting a computer using the NIC. This mechanism allows the computer to boot without relying on a local data storage device (such as a hard disk) or a locally installed operating system.

So I noticed that there is an open-source PXE firmware called iPXE. Building a customized iPXE firmware is simple according to the wiki page of iPXE.

sudo apt update
sudo apt install git gcc binutils make perl liblzma-dev mtools
git clone git://
cd ipxe/src

I need the chain loading function, so I need to add some parameters during the building process like this.

make bin/nm-undionly-20211002-1a.kpxe EMBED=nmboot.ipxe
make bin-x86_64-efi/nm-ipxe-20211002-1a.efi EMBED=nmboot.ipxe

Now I get both legacy BIOS and UEFI PXE firmware embedded my own chain loading script nmboot.ipxe. The script is quiet simple, just chaining the entry point from my HTTP server.


The advantage of this is that it minimizes the size of iPXE firmware for the NIC PXE to be downloaded from the TFTP Server, i.e., the Next Server that has been given by DHCP server. Because of the slow loading speed over TFTP.

My home lab use pfSense as my gateway and DHCP server, the DHCP server config is quite simple.


The next step is just to prepare the file on the http server. Refer here.

It’s done!

继续阅读Build a customized iPXE firmware and deploy a chain loading environment

Use Doxygen to generate documents and diagrams or graphs for your source code

1. apt install required paackages

$ sudo apt update
$ sudo apt install doxygen dia graphviz

2. generate the Doxyfile

$ cd [SOME_PATH]
$ doxygen -g

3. edit the Doxyfile

DIA_PATH = /usr/bin/dia

4. run doxygen

$ doxygen [YOUR_Doxyfile]

5. result examlple

继续阅读Use Doxygen to generate documents and diagrams or graphs for your source code

Note: Add swap file to ubuntu

Check swap file

# swapon -s

Create swap file

# dd if=/dev/zero of=/swap.img bs=1G count=8

Set swap file right

chmod 600 /swap.img

Check swap file right

# ll /swap.img

Format swap file

# mkswap /swap.img

Activate swap file

# swapon /swap.img

Deactivate swap file

# swapoff /swap.img

Check swap

# swapon -s
# free -h

Auto mount swap fs

# echo "/swap.img none swap sw 0 0" >> /etc/fstab

Note: How to reverse proxy a Minecraft server with Nginx

Check your kernel version >= 4.9

uname -a

Enable BBR

sysctl -w net.core.default_qdisc=fq
sysctl -w net.ipv4.tcp_congestion_control=bbr
sysctl -w net.ipv4.tcp_notsent_lowat=16384
sysctl -p

Add stream config to /etc/nginx/nginx.conf

stream {
include /etc/nginx/tcp.d/*.conf;

Create a new config for Minecraft server

server {
listen [PORT];


Test Nginx config

nginx -t

Reload Nginx

nginx -s reload

Optional: Add DNS SRV record

Name     _minecraft._tcp.[YOUR_MINECRAFT_SERVER].tld
Priority [0-65535]
Weight   [0-65535]
Port     [PORT]

Note: How to use rsync without SSH

Server config: /etc/rsyncd.conf

uid = www-data
gid = www-data
max connections = 4
use chroot = no
log file = /var/log/rsyncd.log
pid file = /var/run/
lock file = /var/run/rsync.lock
#hosts allow =
#hosts deny =

path = /var/www/html
comment = rsync
auth users = rsync
ignore errors
read only = yes
list = yes
auth users = rsync
secrets file = /etc/rsyncd.pwd


Secret: /etc/rsyncd.pwd



Server run:

$ rsync --daemon --config=/etc/rsyncd.conf


Client connect:

$ rsync --list-only -rsh=rsh --port=873 [email protected]_TARGET_ADDRESS::rsync


How to boot BPI-M2U/M2B up from SATA device

BPI-M2 Ultra is a powerful Quad-Core ARMv7 based SBC (Single Board Computer) with a powerful Allwinner R40 SoC and 2 GiB DDR3 RAM. BPI-M2 Berry is a Raspberry Pi compatible version of M2U with V40 SoC, an automotive version of R40, and fewer RAM (1 GiB). They are software compatible.

For some reason we want to boot M2U from SATA device for better IO performance. The following photo shown how to connect a SATA HDD to M2U.


From design of Allwinner, the default boot devices sequence has been cured in the BOOT ROM of SoC. The priorities of boot devices from high to low are SD card > NAND > eMMC > NOR SPI Flash.

There is no SATA device right? NP, we can load and boot bootloader and U-Boot form a SD card. By setting the kernel cmdline in the uEnv of U-Boot, it will take over the right from SD card to the SATA device at the second boot stage.

So let’s start.


First prepare a bootable SD card from official released image, like this.

Then open the 256MiB FAT partition called BPI-BOOT.

Open and edit /bananapi/bpi-m2u/linux/720p/uEnv.txt. Attention: which file you need to edit depend on which bootloader you select with bpi-bootsel, the default bootloader will load the environment configuration from 720P.

Find this part of this file.

root=/dev/mmcblk0p2 rootfstype=ext4 rw rootwait bootmenutimeout=10 datadev=mmcblk0p2
console=earlyprintk=sunxi-uart,0x01c28000 console=tty1 console=ttyS0,115200n8 no_console_suspend consoleblank=0
bootopts=enforcing=1 initcall_debug=0 loglevel=4 init=/init cma=256M panic=10
volumioarg=imgpart=/dev/mmcblk0p2 imgfile=/volumio_current.sqsh rw rootwait

Change the three MMC block device to /dev/sda2, like that.

root=/dev/sda2 rootfstype=ext4 rw rootwait bootmenutimeout=10 datadev=sda2
console=earlyprintk=sunxi-uart,0x01c28000 console=tty1 console=ttyS0,115200n8 no_console_suspend consoleblank=0
bootopts=enforcing=1 initcall_debug=0 loglevel=4 init=/init cma=256M panic=10
volumioarg=imgpart=/dev/sda2 imgfile=/volumio_current.sqsh rw rootwait

Now we have a SD card to boot root file system on  the SATA device.


It’s easier to prepare the root filesystem on HDD. Just need to dd the original official released image to the HDD like a SD card. Then expand or resize the root fs like normal. Then power it up.

Now enjoy.

How to adjust the CPU voltage of BPI-M2+

This article introduced how to adjust the VCC-CPUX voltage of the BPI-M2+ with replacing a register of power circuit.



With any hardware change or component soldering.

You will LOST all warranty of your Banana Pi!


When I did something system image build and test tasks for the BPI-M2+ with Allwinner H3 before it on stock last year, I have received a Engineer Sample (ES) form SINOVOIP, the manufacturer of Banana Pi.

The Banana Pi Community Forum have received a lot of reports of the too high VCC-CPUX voltage causing horrible heat issue from other developers.

There is a easy to measure the VCC-CPUX voltage of your BPI-M2+.

This picture shows the Test Point (TP: VCPU) of VCC-CPUX.


If you get a result like me, Congratulation! You got a ES. (R. I. P. the warranty


Okay, the next step is replace the reference register in the feedback circuit of the voltage regulator.



I have no 0402 register in my component library, so I use the 0805. (I’m sorry for that.




And it works. 🙂



According to the AW’s whitepaper H3 should work at 1.008GHz max_freq, but I tested ok with the 1.2GHz sys_config. Lucky~


This is the cpuinfo_cur_freq result of running cpuburn-a7 ( and

The idle CPU temperature is about 15 degrees Celsius lower than work at 1.4 V.

继续阅读How to adjust the CPU voltage of BPI-M2+


du(disk usage),顾名思义,查看目录/文件占用空间大小

$ du -h

$ du -ah



du -h tmp

du -ah tmp

du -h –-max-depth=0

-a或-all 显示目录中个别文件的大小
-b或-bytes 显示目录或文件大小时,以byte为单位
-c或–total 除了显示个别目录或文件的大小外,同时也显示所有目录或文件的总和
-D或–dereference-args 显示指定符号连接的源文件大小
-h或–human-readable 以K,M,G为单位,提高信息的可读性
-k或–kilobytes 以1024 bytes为单位
-l或–count-links 重复计算硬件连接的文件
-L或–dereference 显示选项中所指定符号连接的源文件大小
-m或–megabytes 以1MB为单位
-s或–summarize 仅显示总计
-S或–separate-dirs 显示个别目录的大小时,并不含其子目录的大小
–exclude=<目录或文件> 略过指定的目录或文件

–max-depth=<目录层数> 超过指定层数的目录后,予以忽略

df 用于查看设备的空间使用率

$ df -lh




LNMP一键安装包安装的MySQL默认是开启了日志文件的,如果数据操作比较频繁就会产生大量的日志,在/usr/local/mysql/var/下面产生mysql-bin.0000* 类似的文件,而且一般都在几十MB到几个GB,更甚会吃掉整个硬盘空间,从来导致mysql无法启动或报错。



执行:/usr/local/mysql/bin/mysql -u root -p

输入密码登录后再执行:reset master;

回车后再输入:quit 退出mysql命令模式。

彻底禁用MySQL日志:修改/etc/my.cnf 文件,找到


再这两行前面加上#,将其注释掉,再执行/etc/init.d/mysql restart即可。

如果实在想保留日志,可以在/etc/my.cnf里[mysqld]部分中加入expire_logs_days = 10 然后重启mysql,这样10天就会自动清理日志。