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make ARCH=arm CROSS_COMPILE=arm-hisiv400-linux- menuconfig
进入fs/nfs
vi Kconfig
搜索root
config ROOT_NFS
bool "Root file system on NFS"
depends on NFS_FS=y && IP_PNP
help
If you want your system to mount its root file system via NFS,
choose Y here. This is common practice for managing systems
without local permanent storage. For details, read
<file:Documentation/filesystems/nfs/nfsroot.txt>.
Most people say N here.
NFS_FS必然是已经打开了
IP_PNP是什么?
CONFIG_IP_PNP内核级IP自动配置，即启动时通过内核命令行参数配置，如ip=192.168.0.111...
CONFIG_IP_PNP_XXX即支持XXX协议来配置IP，如及CONFIG_IP_PNP_DHCP=y则支持启动时支持ip=dhcp来配置ip
CONFIG_IP_PNP_XXX即支持XXX协议来配置IP，如及CONFIG_IP_PNP_DHCP=y则支持启动时支持ip=dhcp来配置ip
在当前目录下
grep -Irn "IP_PNP" .
没有收获
在kernel下 net下
grep -Irn "IP_PNP" .
./ipv4/Makefile:36:obj-$(CONFIG_IP_PNP) += ipconfig.o
./ipv4/Kconfig:110:config IP_PNP
./ipv4/Kconfig:121:config IP_PNP_DHCP
./ipv4/Kconfig:123: depends on IP_PNP
./ipv4/Kconfig:138:config IP_PNP_BOOTP
./ipv4/Kconfig:140: depends on IP_PNP
./ipv4/Kconfig:153:config IP_PNP_RARP
./ipv4/Kconfig:155: depends on IP_PNP
./ipv4/ipconfig.c:77:#if defined(CONFIG_IP_PNP_DHCP)
./ipv4/ipconfig.c:80:#if defined(CONFIG_IP_PNP_BOOTP) || defined(CONFIG_IP_PNP_DHCP)
./ipv4/ipconfig.c:83:#if defined(CONFIG_IP_PNP_RARP)
./ipv4/ipconfig.c:125:#ifdef CONFIG_IP_PNP_DHCP
./ipv4/ipconfig.c:1558:#ifdef CONFIG_IP_PNP_DHCP
./ipv4/ipconfig.c:1564:#ifdef CONFIG_IP_PNP_BOOTP
./ipv4/ipconfig.c:1570:#ifdef CONFIG_IP_PNP_RARP
打开Kconfig
config IP_PNP
111 bool "IP:
kernel level autoconfiguration"
112 help
113 This enables automatic configuration of IP addresses of devices and
114 of the routing table during kernel boot, based on either information
115 supplied on the kernel command line or by BOOTP or RARP protocols.
116 You need to say Y only for diskless machines requiring network
117 access to boot (in which case you want to say Y to "Root file system
118 on NFS" as well), because all other machines configure the network
119 in their startup scripts.
120
121 config IP_PNP_DHCP
122 bool "IP: DHCP support"
123 depends on IP_PNP