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关于第一个疑问,可能和mdev有关,以下摘自busybox-1.23.1 mdev.txt:
------------- MDEV Primer
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For those of us who know how to use mdev, a primer might seem lame. For everyone else, mdev is a weird black box that they hear is awesome, but can't seem to get their head around how it works. Thus, a primer.
----------- Basic Use
-----------
Mdev has two primary uses: initial population and dynamic updates. Both require sysfs support in the kernel and have it mounted at /sys. For dynamic updates, you also need to have hotplugging enabled in your kernel.
Here's a typical code snippet from the init script: [0] mount -t proc proc /proc [1] mount -t sysfs sysfs /sys [2] echo /sbin/mdev > /proc/sys/kernel/hotplug [3] mdev -s
Alternatively, without procfs the above becomes: [1] mount -t sysfs sysfs /sys [2] sysctl -w kernel.hotplug=/sbin/mdev [3] mdev -s
Of course, a more "full" setup would entail executing this before the previous code snippet: [4] mount -t tmpfs -o size=64k,mode=0755 tmpfs /dev [5] mkdir /dev/pts [6] mount -t devpts devpts /dev/pts
The simple explanation here is that [1] you need to have /sys mounted before executing mdev. Then you [2] instruct the kernel to execute /sbin/mdev whenever a device is added or removed so that the device node can be created or destroyed. Then you [3] seed /dev with all the device nodes that were created while the system was booting.
For the "full" setup, you want to [4] make sure /dev is a tmpfs filesystem (assuming you're running out of flash). Then you want to [5] create the /dev/pts mount point and finally [6] mount the devpts filesystem on it. |
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