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10.7: Multi-user Screen Sharing System 10.7
When using screen sharing in Lion if another user is logged into your computer you will be asked if you want to run a 'virtual display' with your desktop.

[crarko adds: This was one of the features of Lion I was all excited about, and haven't actually had much chance to work with it. I wonder if the virtual display is treated as a Space owned by the other user. Have any of you worked with this much, and if so, what do you see with performance when multiple users are logged in?]
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10.7: Multi-user Screen Sharing | 9 comments | Create New Account
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10.7: Multi-user Screen Sharing
Authored by: LegoEvan on Nov 04, '11 08:13:14AM

I use this all the time on a remote MacPro. Performance is excellent, even when I'm using 100% of all 8 cores. Once in a while if a graphic is too slick it will hiccup.

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10.7: Multi-user Screen Sharing
Authored by: smitty97 on Nov 04, '11 09:06:25AM

If you use it from a Mac, performance is great. Try it from a regular vnc client on a pc or ipad and it's horrible. Even ones that have been updated to use the user/password Lion login are quite slow. There's no way to reduce the colors to help, and apple probably will not be releasing the source of the method they use to keep it fast.

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10.7: Multi-user Screen Sharing
Authored by: burgerga on Nov 04, '11 10:55:50AM

I have a Mac mini server, and multi user screen sharing works great. Never had any performance issues, smooth as silk. Connecting from my iPhone via Remoter is a little more laggy, especially if I'm on 3G, but it seems acceptable, I'm not gonna be trying to do too much from my phone. Connecting from my phone seems to respect multi user too. It will log me into the admin account and from there I can switch to other accounts, meanwhile the actual computer will stay logged in to whatever account it already was.

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10.7: Multi-user Screen Sharing
Authored by: Makosuke on Nov 04, '11 12:55:29PM

Your dual login is very much treated as your own login, just with a headless windowmanager. This capability has, in simpler form, existed for a while--you could ARD into a headless server Mac and get a GUI, despite it not "mirroring" anything. It was just that until 10.7 you couldn't have more than one at a time.

And it mostly works well, in my relatively limited testing of connecting to a computer that someone else was physically in front of at the same time.

There has, sadly, been a step back in one particular use case of headless Macs common to home theater setups; the workaround for this might even warrant a hint.

The case is thus: You have a Mac Mini connected to your TV through a home theater audio system. You turn the TV and computer on, and use the computer some. Then you turn the TV and audio system off, rendering the Mac headless (it sees its attached monitor disappear entirely).

Under 10.6 (or 10.5), if you then used Screen Sharing to connect to the Mac, you would get the screen, at the HDTV resolution it last saw, just the way you'd left it when you turned the TV off. Very convenient.

Under 10.7.2, this doesn't work so well; when you connect remotely, you get the full-sized screen, but it registers as if the screen is 0 by 0 as far as automatic positioning is concerned. This means that any new windows that open are shoved into the far lower left corner of the screen with nothing but the title bar visible, you are unable to expand most windows (iTunes, say) beyond the minimum size, and all the desktop icons are piled up in the bottom left corner. It's completely unusable.

The workaround is this: If you select "Log out" from the Apple menu, then hit return (the confirmation dialog will be offscreen at the bottom, but the return key hits "ok" by default), it will log you out. You may need to reconnect with screen sharing at this point, but you will now have the login screen; if you log in from there, you will get a fully functioning headless desktop environment. The only (possible) disadvantage is that the resolution (at least for me) defaults to 1680x1050 (which actually works okay, since it doesn't require the remote image to be rescaled to fit on the laptop screen I'm using).

The extra step is a hassle, but it does make the setup at least usable. Hopefully the kinks will get worked out and this will be smoother in a later 10.7 iteration.

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10.7: Multi-user Screen Sharing
Authored by: kevinp on Nov 04, '11 01:58:07PM
When this feature was announced I thought I might be able to use it to open a window into another account (e.g. my admin account) on the same machine without the hassle of entering the password when switching back and forth using fast user switching. I've never been able to get this to work.

Am I missing something?


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10.7: Multi-user Screen Sharing
Authored by: joekewe on Nov 04, '11 02:21:59PM

Just tried ScreenSharing to Localhost and got a "You cannot control your own screen." error. Let me know if you can think of another IP address on my own machine to try.

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10.7: Multi-user Screen Sharing
Authored by: leamanc on Nov 04, '11 03:22:51PM is the IP for localhost, but it will probably give the same error. Alternately, you can put in your actual IP address, but I would fully expect the same error in this case, also.

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10.7: Multi-user Screen Sharing
Authored by: palahala on Nov 06, '11 07:11:28AM

Creating a local SSH tunnel works for me. Enable Remote Login (aka SSH) in System Preferences Sharing, and in Terminal run:

ssh -NL 5901:localhost:5900 localhost

Finally, use Screen Sharing to connect to localhost:5901 (instead of the default port 5900).

However, this is extremely slow on my MacBook Air. Also, one should be very careful not to open a Screen Sharing session to the current screen: that will get one an endless Droste effect...

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Force Share of Remote User's Screen
Authored by: withdave on Nov 05, '11 01:56:54PM

If you try to gain shared access to a remote login screen being used by the remote user they will be asked to give you permission do to so.

However, there is a way around this if you can log in to another account on the remote machine and also know the password for the current remote user's account. First, connect to a virtual display using your own account. Then log out. The standard lion login will show allowing you to login to the same account as the currently active remote user. At that point you can login to their account and get access to the user's remote screen without a permission request. Screen sharing does display a Status Menu on the right side of their menu indicating their screen is being shared.

Very handy when doing remote maintenance to other Lion Macs in my home. I don't have to walk to the remote Mac and give myself permission.

Originally I thought this was a security risk, but it isn't since you have to know the user's password to gain access in this fashion.

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