Overview
D1237058564
Astevie
#
#WHY PLAN 9?
#
#Why Plan 9 indeed. Isn't Plan 9 just another Unix clone? Who cares?
#
#Plan 9 presents a consistent and easy to use interface. Once you've
#settled in, there are very few surprises here. After I switched to
#Linux from Windows 3.1, I noticed all manner of inconsistent
#behavior in Windows 3.1 that Linux did not have. Switching to Plan 9
#from Linux highlighted just as much in Linux.
#
#One reason Plan 9 can do this is that the Plan 9 group has had the
#luxury of having an entire system, so problems can be fixed and
#features added where they belong, rather than where they can be. For
#example, there is no tty driver in the kernel. The window system
#handles the nuances of terminal input.
#
#If Plan 9 was just a really clean Unix clone, it might be worth
#using, or it might not. The neat things start happening with
#user-level file servers and per-process namespace. In Unix, /dev/tty
#refers to the current window's output device, and means different
#things to different processes. This is a special hack enabled by the
#kernel for a single file. Plan 9 provides full-blown per-process
#namespaces. In Plan 9 /dev/cons also refers to the current window's
#output device, and means different things to different processes,
#but the window system (or telnet daemon, or ssh daemon, or whatever)
#arranges this, and does the same for /dev/mouse, /dev/text (the
#contents of the current window), etc.
#
#Since pieces of file tree can be provided by user-level servers, the
#kernel need not know about things like DOS's FAT file system or
#GNU/Linux's EXT2 file system or NFS, etc. Instead, user-level
#servers provide this functionality when desired. In Plan 9, even FTP
#is provided as a file server: you run ftpfs and the files on the
#server appear in /n/ftp.
#
#We need not stop at physical file systems, though. Other file
#servers synthesize files that represent other resources. For
#example, upas/fs presents your mail box as a file tree at
#/mail/fs/mbox. This models the recursive structure of MIME messages
#especially well.
#
#As another example, cdfs presents an audio or data CD as a file
#system, one file per track. If it's a writable CD, copying new files
#into the /mnt/cd/wa or /mnt/cd/wd directories does create new audio
#or data tracks. Want to fixate the CD as audio or data? Remove one
#of the directories.
#
#Plan 9 fits well with a networked environment, files and directory
#trees can be imported from other machines, and all resources are
#files or directory trees, it's easy to share resources. Want to use
#a different machine's sound card? Import its /dev/audio. Want to
#debug processes that run on another machine? Import its /proc. Want
#to use a network interface on another machine? Import its /net. And
#so on.
#
#Russ Cox
#