Re: devfs

Michael O'Reilly (michael@metal.iinet.net.au)
08 Jan 1998 16:12:22 +0800


"Albert D. Cahalan" <acahalan@cs.uml.edu> writes:

> I've seen a few "nothing is broken" posts. Things _are_ broken.
> Leaving aside the issue of a bloated /dev full of junk I don't
> have, there are some serious reasons for a devfs. It needs to
> be a real devfs too, not some weak hack.

The reasons below amount to "we need a devfs because"

"#1. Non-unix fileystems don't support devices". Excuse me while I
cry. They also don't support a/c/m/times, hard links, long case
sensitive filenames, reasonable performance, unix sockets, and inode
numbers. Why focus on devices? Face is, non-unix filesystems will
never have the feature set of unix filesystems. That's what the
'non-unix' bit means.

"#2. Ptys aren't very clean". No kidding. But there are much much
better ways of fixing the ptys than building a devfs. Ptys have a
fairly specific problem that nothing else in the /dev world does.

> *** Read-only filesystems ***
> [ .. ] The Linux root filesystem can not be read-only because the
> normal /dev must be read-write to allow tty ownership changes.

No to mention utmp, wtmp, any sort of logging, etc. Fact #1. A read
only filesystem is always going to be a very special case. Fact
#2. Nothing stops you building pty's on a seperate read-write
filesystem.

> *** NTFS ***
non-unix file system.

> *** PTY security ***
[ Pty ownership issues ]