在嵌入式Linux系统中，有时需要关闭调试串口，不让调试口输出信息，这也可以保证系统程序的安全。关闭调试串口输出的方法也很简单，可以在uboot阶段通过修改参数来实现，参数设置如下：
setenv bootargs 'mem=756M console=null,115200 initrd=0x82600000,0x700000 , root=/dev/ram0 init=nuxrc mtdparts=hi_sfc:1M(boot),1M(logo),5M(kernel),7M(rootfs),26M(qtlib),12M(app),-(config);hinand:-(nand-user)'
这里面主要是这一句是关闭调试口输出：
console=null
设置完成后记得保存（sav），然后重启设备，通过串口可以看到，内核启动后，调试信息就没有了：
System startup
U-Boot 2010.06-dirty (Jun 10 2020 - 10:51:22)
Check Flash Memory Controller v100 ... Found
SPI Nor(cs 0) ID: 0xc2 0x20 0x1a
Block:64KB Chip:64MB Name:"MX25L(512)XX"
SPI Nor total size: 64MB
SPI Nand(cs 1) ID: 0xc8 0xf4 Name:"5F4GQ4UAYIG"
Block:128KB Page:2KB Chip:512MB*1 OOB:64B ECC:4bit/512
ECC provided by Flash Memory Controller
SPI Nand total size: 512MB
In: serial
Out: serial
Err: serial
65536 KiB hi_fmc at 0:0 is now current device
jpeg decoding ...
<<addr=0x82000000, size=0x20000, vobuf=0x9f000000>>
mmu_enable
<<imgwidth=1024, imgheight=768, linebytes=2048>>
decode success!!!!
decode jpeg!
stMaxRect.u32Width:1024, stMaxRect.u32Height:768.
HDMI_INFO:DispFmt2HdmiTiming[402] ,Non CEA video timing:17
HDMI_INFO:Hdmi_PixelFreqSearch[146] ,u32Fmt17.
dev 0 opened!
graphic layer 0 opened!
Hit any key to stop autoboot: 0
65536 KiB hi_fmc at 0:0 is now current device
## Booting kernel from Legacy Image at 82100000 ...
Image Name: Linux-3.18.20
Image Type: ARM Linux Kernel Image (uncompressed)
Data Size: 3372785 Bytes = 3.2 MiB
Load Address: 80008000
Entry Point: 80008000
Loading Kernel Image ... OK
OK
Starting kernel ...
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