From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jim Choate To: <9fans@cse.psu.edu> Cc: , In-Reply-To: <200305181305.h4ID5h524391@augusta.math.psu.edu> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Subject: [9fans] Re: Free Plan 9 "shell" accounts? Date: Sun, 18 May 2003 08:43:19 -0500 Topicbox-Message-UUID: af60e450-eacb-11e9-9e20-41e7f4b1d025 On Sun, 18 May 2003, Dan Cross wrote: > I don't understand what this means; doesn't the ability to start a > process on a remote machine (``process pool'') mean you can start a > shell on it? Yes, if you want to look at it by the 'process tied to machine' viewpoint. Plan 9 means much more. The concept of 'starting a shell on it' is a rather non-distributed way of thinking about Plan 9 though. An archaic viewpoint if you will. Plan 9 has per process namespace, and there is really nothing that says the namespace that a particular process is running on a particular piece of hardware are shared. In other words the resources for a given shell don't necessarily have to reside on that machine. In other words the process server doesn't have to share any of its kfs resources into the namespace of the process). The namespace doesn't even have to come from a single machine. So, if you've got a process that has it's I/O connected to your machine, and various namespaces transitively mounted from machines other than the process server executing the job, can you really say the shell is running on 'that machine'? I'd say "No". If you have a process server executing a job that spawns multiple processes, Tower of Hanoi or a factorial might be a job that would do for an example, and those processes are running on different machines; can you say that the program runs on 'that machine'? I'd say "No", You're running a 'shell on a machine' and that machine hiccups, with traditional operating systems the only result is to throw an error condition and halt. On Plan 9 it's possible that in cases that if a machine were to die the namespace resources (which we'll assume aren't on the process server native) are saved and the machine that started the process would simply re-init that job on another processer, without the user even knowing about it. Is that running that program 'on a machine'? I'd say "No". There are many other examples I could think of, you will too; eventually. Plan 9 has the unique advantage of being able to create a distributed virtual machine. This means that where the job runs is irrelevant, and where the resources of the namespace exist is irrelevant. Plan 9 is not so much 'where' but 'how to impliment'. To worry about the specific machine is a pretty archaic viewpoint that is not really compatible with understanding what one can get out of Plan 9. Plan 9 is a -distributed- operating system. This means that you have to think of 'process clouds' and many resources clustered together to form a namespace. The fact the namespace is -per process- is what takes it a step above the 'run a shell on a machine' perspective. You have to get past thinking of Plan 9 as a OS 'on a machine' and think of it as a OS -across machines-. Note the plural in that, it's critical to understanding the true power of the OS from the perspective of the user. [1] If you really want to have an OS on -a machine- then Plan 9 will bring you nothing of interest. Stick with traditional operating systems. If you want to join a -community of resources- then look into Plan 9, it will surpise you. [2] Hope that helps clear up your confusion...;) [1] This goes right to the heart of one of my issues with the Plan 9 community here with regard to lack of understanding of 'user' space as compared to looking at everything as a 'developer' space issue. Such is the flaw of having a goal of keeping a technology limited to a niche (ie research OS). [2] I've mentioned this distinction many times in the past, and it amazes me that many long time users of Plan 9 still don't 'get it'. -- ____________________________________________________________________ We are all interested in the future for that is where you and I are going to spend the rest of our lives. Criswell, "Plan 9 from Outer Space" ravage@ssz.com jchoate@open-forge.org www.ssz.com www.open-forge.org --------------------------------------------------------------------