The Most Awesome, Least-Advertised Fedora 17 Feature

Wunschkonzert, Ponyhof und Abenteuerspielplatz ^ | May 1st | Lennart Poettering

[Halfmanhalfamazing]

There's one feature In the upcoming Fedora 17 release that is immensly useful but very little known, since its feature page 'ckremoval' does not explicitly refer to it in its name: true automatic multi-seat support for Linux.

A multi-seat computer is a system that offers not only one local seat for a user, but multiple, at the same time. A seat refers to a combination of a screen, a set of input devices (such as mice and keyboards), and maybe an audio card or webcam, as individual local workplace for a user. A multi-seat computer can drive an entire class room of seats with only a fraction of the cost in hardware, energy, administration and space: you only have one PC, which usually has way enough CPU power to drive 10 or more workplaces. (In fact, even a Netbook has fast enough to drive a couple of seats!) Automatic multi-seat refers to an entirely automatically managed seat setup: whenever a new seat is plugged in a new login screen immediately appears -- without any manual configuration --, and when the seat is unplugged all user sessions on it are removed without delay.

In Fedora 17 we added this functionality to the low-level user and device tracking of systemd, replacing the previous ConsoleKit logic that lacked support for automatic multi-seat. With all the ground work done in systemd, udev and the other components of our plumbing layer the last remaining bits were surprisingly easy to add.

Currently, the automatic multi-seat logic works best with the USB multi-seat hardware from Plugable you can buy cheaply on Amazon (US). These devices require exactly zero configuration with the new scheme implemented in Fedora 17: just plug them in at any time, login screens pop up on them, and you have your additional seats. Alternatively you can also assemble your seat manually with a few easy loginctl attach commands, from any kind of hardware you might have lying around. To get a full seat you need multiple graphics cards, keyboards and mice: one set for each seat. (Later on we'll probably have a graphical setup utility for additional seats, but that's not a pressing issue we believe, as the plug-n-play multi-seat support with the Plugable devices is so awesomely nice.)

Plugable provided us for free with hardware for testing multi-seat. They are also involved with the upstream development of the USB DisplayLink driver for Linux. Due to their positive involvement with Linux we can only recommend to buy their hardware. They are good guys, and support Free Software the way all hardware vendors should! (And besides that, their hardware is also nicely put together. For example, in contrast to most similar vendors they actually assign proper vendor/product IDs to their USB hardware so that we can easily recognize their hardware when plugged in to set up automatic seats.)

Currently, all this magic is only implemented in the GNOME stack with the biggest component getting updated being the GNOME Display Manager. On the Plugable USB hardware you get a full GNOME Shell session with all the usual graphical gimmicks, the same way as on any other hardware. (Yes, GNOME 3 works perfectly fine on simpler graphics cards such as these USB devices!) If you are hacking on a different desktop environment, or on a different display manager, please have a look at the multi-seat documentation we put together, and particularly at our short piece about writing display managers which are multi-seat capable.

[PapaBear3625]

The impression I get from the article and linked article is that you can attach one of these "Plugable" devices to one of your computer's USB ports, attach a monitor/keyboard/mouse to the Plugable device, and you have another user seat working off your computer.

[Ernest_at_the_Beach]

Is this code exclusive to Gnome3?

[Moose4]

Yeah, we’d buy a Compaq desktop usually, 386/20 or 386/25, slap a tape backup drive in the front and a massive 80 MB hard drive in the body, then put in one or two 8-port serial cards (DigiBoards, I think) with these huge 25-pin serial octopus dongles hanging out the back. We’d install SCO System V Unix on it, then take it out to the client and set it up with Wyse 50 (or similar) terminals after installing accounting software on it. And thus you’d have a company running 12 or so terminals on a 25 MHz 386 covering their entire business. I think back to those days and honestly wonder how we could make that work.

(BTW, I sure don’t miss the days of pinning serial cables by hand. UGH.)

}:-)4

[Halfmanhalfamazing]

At the moment, yes I do believe that most it is. Red Hat is a Gnome-centric organization. But I don’t think it will take long for the KDE-types to catch up, or any of the others for that matter.

Whatever code was not done for Gnome was done for ‘plumbing level’ software, as is suggested in the article. The Fedora feature page makes it a bit more clear.

http://fedoraproject.org/wiki/Features/ckremoval

===========We need smaller changes in: X11, gdm, CK, udev, dbus, plymouth, PK, NM, accountsservice==========

[unixfox]

(BTW, I sure don’t miss the days of pinning serial cables by hand. UGH.)

I hated that! And don't get me started with trying to get serial printers to handshake with the Digiboards. Good grief!

[Ernest_at_the_Beach]

KDE and Gnome 3 are not on my Favorite list....at this time.

[PAR35]

It means lots of people using one single computer at the same time. It takes multi-user to the next step. <

Kind of like the 1980s when we had DECs?

[Mycroft Holmes]

The impression I get from the article and linked article is that you can attach one of these "Plugable" devices to one of your computer's USB ports, attach a monitor/keyboard/mouse to the Plugable device, and you have another user seat working off your computer.

Pretty much. The hardware is essentially a USB 2.0 hub with an embedded VGA card and audio stuff. The hardware bundles the video/keyboard/mouse/audio into one USB device which makes it easy for the software to sort out on its end.

I think it's pretty cool that we can now do video over a vanilla serial interface that just plugs right in. Thank you Ajay Bhatt and Intel.

I, for one, welcome our new Thin Client Overlords /.

[Erasmus]

I think back to those days and honestly wonder how we could make that work.

No graphics then, graphics now.

[KoRn]

This is making me think ‘virtual desktop’, such as VMware’s VDI, only being run on the local workstation at the user level. Am I terribly off-base here?

Thin clients>>Virtual desktops is pretty sweet. I started using it at work in a few departments, and it’s awesome. You can have all of the desktops in the datacenter, a cheap thin client that’ll practically last forever not needing replacement, and if a user’s hardware requirements increase, with a few mouse clicks you can give them more resources. You can also use the ‘checkout’ feature to allow certain users to even take their ‘workstation’ home, or travel with them on mobile devices(laptops, Tablets, ect). Malware infection(for windows users)? Revert that sucker to a snapshot and forget about it.

It almost makes the PC itself obsolete for most uses. To setup another computer, it’s literally as easy as a ‘copy/paste’ in Windows. Literally nothing to it. For people starting out these days, I would strongly encourage techs to learn server hardware, networked storage, and Virtualization(vmware specifically). That’s the direction where everything has gone, or is going.

[Pearls Before Swine]

I wasn’t aware this was on the horizon. Thanks.

Truly a “beefy miracle.”

(For those who don’t know, that’s the pet name for release 17 of Fedora Core).

[Halfmanhalfamazing]

============This is making me think ‘virtual desktop’=========

Virtual desktop on steroids. Consider sitting at one table, with a family member to your left, a friend to your right, and all three of you are using the exact same computer, all logged in doing very different things with your own keyboards, your own mice, and your own monitors. (see the picture and video I posted above)

-—————It almost makes the PC itself obsolete for most uses.-—————

Not at all. All three of you(your friend, family member, and yourself) are connected to one single PC. A laptop would easily work as well, hardware limitations notwithstanding.

-——————To setup another computer———————

Not a whole different computer. These are not stand alone thin clients. They’re very different.

To my knowledge, USB has a limit of 127 devices.

So your maximal end result could be 127 users all using one computer. That’s a lot of tables, keyboards, mice, and monitors. But you would save quite a pretty penny by eliminating 126 towers! Just make sure you invest in twin 8 core opterons. :-)

[Halfmanhalfamazing]

This should help visualize:

This assumes 20 monitors, 20 keyboards, 20 mice, and one single PC.

[KoRn]

"Not at all. All three of you(your friend, family member, and yourself) are connected to one single PC. A laptop would easily work as well, hardware limitations notwithstanding."

I should have clarified on that point. I was assuming enterprise type environments with thin clients. Not home/residential users. The PC will continue to be around for a very long time there(especially as long as folks do PC gaming).

[2 Kool 2 Be 4-Gotten]

I want to say that Solaris (or SunOS not sure) had this back in circa 1995. Still seems like a good idea though.

[Halfmanhalfamazing]

Oh. Well, I could’ve misread it too. It happens.

But this could just as easily be used in the enterprise too.

Those users doing basic/moderate database, or office, call centers, or whatever work don’t need their own dedicated computer. You could easily have one tower computer serving 4 to 6 or more cubicles a piece.

Computers have gotten so powerful lately, that using office or browsing the web, playing music, preparing presentations, emails....... so much of what people do today with their computers(enterprise or otherwise) is the equivalent of shooting peas at an elephant. And while you’re preparing that word document, your computer is just sitting there idle.

Multiseat is all about taking advantage of that idle time.

[KoRn]

Yeah, in most machines, the resources are just sitting there not being used. That’s what makes virtualization so attractive for servers.

Like PCs, most servers are also just sitting there idle. Even during periods of high utilization, machines these days have so much ‘juice’, the demand barely scratches the surface of their capability. Instead of having an OS sitting there dedicated to a single host, why not install ESX and run the server as a VM, and run 10 or so similar servers on the same hardware to get your money’s worth.

Such a wonderful example of this... At work, around 2 years ago I had tested virtualization enough to be confident in it for use in our datacenter. I did “P2V” migrations of around 70%(80 or so boxes) of our servers down to 5 clustered ESX hosts. I didn’t really publicize it within our department when I was doing the migrations, in case something ‘blew up’, but it all went without any major issues.

When I was done, I invited my director to come down to the Datacenter(he rarely goes in there), and as soon as he walked in the door I thought he was going to faint, because the room was nearly quiet and most of the servers were turned off. I then guided him to a corner of the room where I had the rack with the 5 hosts in it, and told him that all of the servers that were powered off were now running “here”. I think it took me a week to explain the technology to him before he even began to grasp it. After these 2 years of it all running great, I STILL don’t think he really understands how it works. He just knows that it does, and that’s all that matters to him I guess. lol

(my apologies for the lengthy post)