Re: NEWBIE question Re: static or dynamic /dev
Richard Owlett <firstname.lastname@example.org> writes:
> Roger Leigh wrote:
>> On Fri, Apr 05, 2013 at 05:42:32AM -0700, sting wing wrote:
>>> Question: how does a person know if their /dev is a static or dynamic /dev
>> % findmnt /dev
>> TARGET SOURCE FSTYPE OPTIONS
>> /dev devtmpfs devtmpfs rw,size=249844k,nr_inodes=62461,mode=755
>> Unless you have taken very special steps to avoid it, you will
>> always have a dynamic /dev. This has been the case for many
>> many years now. udev uses a tmpfs mounted on /dev (and more
>> recently a devtmpfs mounted on /dev).
>> If there's nothing mounted on /dev, then you will have a static
>> /dev. However, if using Linux, the chances of having a static
>> /dev on a contemporary system are vanishingly small--you'd have
>> to intentionally alter the boot scripts to avoid a dynamic /dev.
> What does it mean when /dev is said to be static? dynamic?
> What should I be reading about?
Many years ago, /dev was a directory containing entries called "special
files" (which essentially meant mappings from filenames to device
drivers). It was the responsibility of the system administrator to make
sure that any time a device was added, a corresponding special file was
added to /dev. In such a system, /dev is static.
In a modern system, /dev doesn't physically exist on disk at all: it's
a special kind of filesystem that lives only in the memory of the
computer, called a tmpfs (temporary filesystem). Daemons detect what
hardware is available, and automatically create the right special files
in this filesystem. This is a dynamic /dev.