When does the /dev/sda1 node comes into being ?
hi:) During booting period .every device will have a node at /dev/ folder. what is the detail of ths procedure? thanks!
On Wed, 06 Feb 2013 01:26:44 +0800, horseriver said:
During booting period .every device will have a node at /dev/ folder. what is the detail of ths procedure?
'man udev'. Although the details are a tad murkier for kernels after 2.6.32 that include CONFIG_DEVTMPFS in the config. Also, note that not all systems will have a /dev/sda1 - that assumes a partition table on a particular type of disk handled by a specific device driver. If that disk has no recognizable partition table, it will just have a /dev/sda entry. If the disk is driven by a different driver, you'll see /dev/hda entries instead. And if your boot storage device is an SD card or something, you may have /dev/mmc0 or other entries. And this: [~] ls -l /dev/sdre1 brw-rw---- 1 root disk 133, 385 2012-11-27 05:17 /dev/sdre1 is how I pay the rent. :) (Bonus points if you can figure out why my system reports that. :)
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@gmail.com> wrote:
hi:)
During booting period .every device will have a node at /dev/ folder. what is the detail of ths procedure?
thanks!
_______________________________________________ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
-- Regards, Peter Teoh
participants (3)
-
horseriver -
Peter Teoh -
Valdis.Kletnieks＠vt.edu