/dev file system

sryzdn · 12-31-2014, 06:21 AM

Hi,

I was reading a note that says:

Quote:

The 2.4.x and newer kernels include support for a dedicated
/dev filesystem, which obviates the need for files in a disk-based
/dev directory; so, in some sense, /dev can reside on a separate
filesystem, although not a separate partition.

what are the advantages of having /dev as a separate filesystem over having it as a disk-based partition/directory?

veerain · 12-31-2014, 06:59 AM

With linux 2.6.x and newer disk based dev is recommended. It is managed by udev or devtmpfs + some. In 2.4 devfs was introduced but it has been deprecated since then. With newer kernels udev or devtmpfs with mdev/hotplug is used.

sryzdn · 12-31-2014, 07:35 AM

Quote:

Originally Posted by veerain

With linux 2.6.x and newer disk based dev is recommended. It is managed by udev or devtmpfs + some. In 2.4 devfs was introduced but it has been deprecated since then. With newer kernels udev or devtmpfs with mdev/hotplug is used.

You want to say that having udev utility has changed the trend and now having /dev as a disk directory is popular?
What is the reason of going and coming with disk-base directory and filesystem?

jpollard · 12-31-2014, 05:29 PM

A fairly general explanation is at:

http://unix.stackexchange.com/questi...vtmpfs-for-dev

The main use without udev would be for system with a relatively stable set of disks (where nothing really changes). The dev directory tree is supported in memory by the kernel identifying the devices attached. It does not deal with access permissions other than the defaults built in, and that is where udev can enter the picture as a notification agent to other userspace tools.

For an embedded use, /dev is fairly finished as soon as the kernel is running.