rcS中启动udevd

在目标板的/etc/init.d/rcS文件中以如下命令启动udevd：

# start udevd.
/sbin/udevd -d
/sbin/udevtrigger

下面是启动过程，从网络配置开始：

IP-Config: Guessing netmask 255.255.255.0
IP-Config: Complete:
     device=eth0, addr=192.168.37.244, mask=255.255.255.0, gw=255.255.255.255,
     host=192.168.37.244, domain=, nis-domain=(none),
     bootserver=255.255.255.255, rootserver=192.168.37.200, rootpath=
Looking up port of RPC 100003/2 on 192.168.37.200
eth0: link up (10/Half)
eth0: link down
eth0: link up (10/Half)
Looking up port of RPC 100005/1 on 192.168.37.200
VFS: Mounted root (nfs filesystem) on device 0:12.
Freeing init memory: 120K
rm: /tmp: is a directory
rm: /var: is a directory
udevd[859]: udev: missing sysfs features; please update the kernel or disable the kernel's CONFIG_SYSFS_DEPRECATED option; udev may fy

the program '/bin/busybox' called '/sbin/udevtrigger', it should use 'udevadm trigger <options>', this will stop working in a future e
udevadm[860]: the program '/bin/busybox' called '/sbin/udevtrigger', it should use 'udevadm trigger <options>', this will stop workine

/ #

最后能顺利进入shell界面，但是提示了udevd与内核的一个选项CONFIG_SYSFS_DEPRECATED似乎不兼容。

因为嵌入式系统的内核可以很方便地更改，重新编译内核：

make ARCH=arm CROSS_COMPILE=arm-linux- menuconfig

使用/操作符搜索一下CONFIG_SYSFS_DEPRECATED，发现原来在General setup下确实被设定为y，

进入General setup选项，将Create deprecated sysfs layout for older userspace tools前面的*取消，保存退出。

重新编译生成uImage U-Boot中专用的二进制压缩文件，在U-Boot命令行界面将新编译生成的uImage烧写到Flash中，reset重启目标板。

重启完成，看到如下结果：

IP-Config: Guessing netmask 255.255.255.0
IP-Config: Complete:
     device=eth0, addr=192.168.37.244, mask=255.255.255.0, gw=255.255.255.255,
     host=192.168.37.244, domain=, nis-domain=(none),
     bootserver=255.255.255.255, rootserver=192.168.37.200, rootpath=
Looking up port of RPC 100003/2 on 192.168.37.200
eth0: link up (10/Half)
eth0: link down
eth0: link up (10/Half)
Looking up port of RPC 100005/1 on 192.168.37.200
VFS: Mounted root (nfs filesystem) on device 0:12.
Freeing init memory: 120K
rm: /tmp: is a directory
rm: /var: is a directory
the program '/bin/busybox' called '/sbin/udevtrigger', it should use 'udevadm trigger <options>', this will stop working in a future e
udevadm[861]: the program '/bin/busybox' called '/sbin/udevtrigger', it should use 'udevadm trigger <options>', this will stop workine

/ #

可以看到，原来的关于udev的missing sysfs features已经消失。只是使用上用法有所不同了。