Re: When does the /dev/sda1 node comes into being ?

[Peter Teoh <htmldeveloper@xxxxxxxxx>]

i think it depends.   some are softlinks in /dev/ some are created by udev after udevd read the configuration file, many scenario involved (just search for "util_create_path" inside udev source codes and u can what are all the situation).

but for harddisk (whose partition is also the rootfs) /dev/sda is created during kernel booting up (inside the initrd file, just gunzip and extract out the cpio file, eg, view the file scripts/local and u can see it make the /dev/sdXXXX nodes based on /sys/block/XXXX information, which in turn depends on the kernel calling xxxx_device_register() functions (there a few variations of them - organized hierarchically)).   

on the other hand, if /dev/sda is not the rootfs, but just a normal harddisk listed in /etc/fstab, then likely it is mounted by udev, detecting it, and then calling (indirectly from userspace to kernel) sd_probe_async(), which will then printk() out the "Write Protect is off" message in your dmesg output - anytime u plug in the harddisk u can see this.

On Wed, Feb 6, 2013 at 1:26 AM, horseriver <horserivers@xxxxxxxxx> wrote:

hi:)

  During booting period .every device will have a node at /dev/ folder.
  what is the detail of ths procedure?

thanks!

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--
Regards,
Peter Teoh

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