Re: NEWBIE question Re: static or dynamic /dev
Joe Pfeiffer wrote:
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.
Thank you Joe and Kevin.