pepitoGrillo
Posts: 13
Joined: Sat Oct 27, 2012 5:55 pm

remote access

Sun Oct 28, 2012 6:06 pm

Hi guys, some questions I would like to solve:

1. What is X11 or X Window System and what kind of security does it have?
2. Is X11 the same as ssh or VNC?
3. And what is best among all these, VPN and if there is any other way for remote desktop?
4. What are the best programs for remote control? (lightweight)

5.For raspberrypi access from a remote computer (including LAN) or vice versa which is the best and safest?

6.How to access from an Android phone? (any program?)

smartpatrol
Posts: 23
Joined: Thu Oct 18, 2012 2:28 am

Re: remote access

Sun Oct 28, 2012 7:55 pm

Answers:
1. On a local lan its fine over low bandwidth its not good
2. No
3. VNC over an SSH tunnel would be secure.
4. The best remote admin tool is a terminal session using ssh.
5. see 4
6. VNC might work but it depends on the network.

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raspberrypiguy1
Posts: 379
Joined: Sun Sep 02, 2012 7:01 pm

Re: remote access

Sun Oct 28, 2012 8:00 pm

I recently did a tutorial on this... It answers some BUT not all of your questions!

Here is my channel:

http://www.youtube.com/user/TheRaspberr ... ature=mhee

The Raspberry Pi Guy ;)
Matt, The Raspberry Pi Guy YouTube channel, author of Learn Robotics with Raspberry Pi, available now: http://mybook.to/raspirobots, Computer Science & Electronics Undergraduate at The University of Edinburgh

ghans
Posts: 7883
Joined: Mon Dec 12, 2011 8:30 pm
Location: Germany

Re: remote access

Sun Oct 28, 2012 8:26 pm

1. The first computers did not have a point-and-click interface. They had a command-line interface (CLI).
Linux is still more powerful from the CLI in my opinion.
The X window system (X11) makes the Graphical User Interface (GUI) work under Linux (simplified explanation) .
In Raspbian the GUI is LXDE running "on top" of X11 , in Windows it's the Desktop and the Explorer ,
in Mac OS X it's Aqua (or something.)
Security: I believe a 15 year old could "overhear" a X window session after some googling.

2. SSH is the CLI over any network (including the Internet) , encrypted and therefore safe.
VNC works a bit like screenshots sent over the Net and is ineffective , slow and not safe.
3. I would suggest X forwarding over SSH instead of your choices.
4. I use MobaXTerm for Windows. A Google search will help you to find YOUR personal favorite.
5. See 3.
6. There are other things "like" VNC : (X)RDP , Nomachine NX /FreeNX , TeamViewer , solutions from Citrix.
The latter two are not available on the Pi, but I bet EVERY of these protocols has a "viewer" or client app
on the market.

ghans
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pepitoGrillo
Posts: 13
Joined: Sat Oct 27, 2012 5:55 pm

Re: remote access

Sun Oct 28, 2012 11:38 pm

Thanks everyone :-)
1. On a local lan its fine over low bandwidth its not good
I don't understand, why?


X Window makes work GUI on Linux, doesn't it?
KDE and GNOME are also based on X Window, don't they?
if so I think I have understood
3. I would suggest X forwarding over SSH instead of your choices.
:shock: You want to say i can use GUI via ssh? Sorry but i didn't understand this sentence at all

smartpatrol
Posts: 23
Joined: Thu Oct 18, 2012 2:28 am

Re: remote access

Mon Oct 29, 2012 1:37 am

pepitoGrillo wrote:Thanks everyone :-)
1. On a local lan its fine over low bandwidth its not good
I don't understand, why?


X Window makes work GUI on Linux, doesn't it?
KDE and GNOME are also based on X Window, don't they?
if so I think I have understood
3. I would suggest X forwarding over SSH instead of your choices.
:shock: You want to say i can use GUI via ssh? Sorry but i didn't understand this sentence at all
Chelling X windows remotely can consume a lot of bandwidth and will be very slow over a slow netowrk connection. VNC would be a better choice the problem is that is very insecure so it suggested that you secure it by running it over a SSH Tunnel.

X windows is a program not unlike windows 3.1 on DOS the best and most secure remote interface for a command line OS like Linux is the command line. You really should not depend on a GUI to manage linux systems remotely.

bgirardot
Posts: 518
Joined: Wed Oct 10, 2012 6:20 am
Location: Switzerland

Re: remote access

Mon Oct 29, 2012 7:21 am

pepitoGrillo wrote:Thanks everyone :-)
1. On a local lan its fine over low bandwidth its not good
I don't understand, why?


X Window makes work GUI on Linux, doesn't it?
KDE and GNOME are also based on X Window, don't they?
if so I think I have understood
3. I would suggest X forwarding over SSH instead of your choices.
:shock: You want to say i can use GUI via ssh? Sorry but i didn't understand this sentence at all
Yes, X Window is the basic underlying system that KDE and GNOME both use to display your "desktop". I think KDE might be using something called Qt now instead of X Window, but essentially you understand the situation correctly.

And yes, you can actually use SSH, an encrypted and secure communication protocol, to run a "desktop" for your RPi on another computer. I am pretty sure the "desktop" literally runs on the remote computer, so the remote computer must also support the X Windows system.

Or, you can use VNC to do something similar but slightly different. With VNC, the "desktop" runs on your RPi and you are just viewing that desktop on the remote computer. This means you can use the VNC solution with machines that do not support or run the X Windows system. I use VNC on my phone to view the desktop of my MS Windows XP machine. But you could run a desktop on your RPi and then use VNC on just about anything to view the desktop running on your RPi.

pepitoGrillo
Posts: 13
Joined: Sat Oct 27, 2012 5:55 pm

Re: remote access

Mon Oct 29, 2012 1:05 pm

Ok, I have seen some tutorial and there are people who use RSA to encrypt ssh.
SSH has security yet. What's the difference?
What can a sniffer to see?

bgirardot
Posts: 518
Joined: Wed Oct 10, 2012 6:20 am
Location: Switzerland

Re: remote access

Mon Oct 29, 2012 1:25 pm

I believe that RSA is just one of the methods you can use for "authentication" or logging in, the other common method is just a user name and password to log in.

I am pretty sure that RSA is only used for creating the public and private keypairs for authentication so you don't have to enter a user name and password every time you want to make a secure connection to a particular machine.

I think the SSH protocol itself handles the encryption of the actual data between the two machines.

A sniffer is only going to see what looks like random garbage if it is sniffing any SSH connection.

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penguintutor
Posts: 394
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Location: UK
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Re: remote access

Mon Oct 29, 2012 2:26 pm

1. What is X11 or X Window System and what kind of security does it have?

X Windows / X11 is the basic graphical system used on Linux. If you look at X11 on it's own then it is very grey and basic (doesn't include minimise / maximise buttons etc). It's then used in conjunction with a Window Manager which makes it user friendly and improves its appearance.

X11 is designed to be network enabled, so you can run an application on one server and it's GUI appears on a different computer.

LXDE (on Raspberry Pi) / Gnome / XFce and KDE are examples of Window Managers.

Qt is a programming framework that KDE uses (Gtk is used by others) - it is not part of X11.

2. Is X11 the same as ssh or VNC?

No VNC is a separate application that provides either a separate virtual screen, or that allows you to view the current screen.

X11 only exports the particular application requested, whereas VNC works on the entire screen.

3. And what is best among all these, VPN and if there is any other way for remote desktop?

Tightvnc is the best from a bandwidth point of view.


4. What are the best programs for remote control? (lightweight)

As above - Tightvnc

5.For raspberrypi access from a remote computer (including LAN) or vice versa which is the best and safest?

None are "safe" by default.
To make them safe you need to run over ssh.

X11
ssh -X pi@<ipaddr>
Then run the application

VNC
ssh -L x:localhost:y pi@<ipaddr>
(x is the local port and y is the remote port - eg. 5901 for both)

or use ssvnc (which includes built-in ssh)

you should then setup vnc so that it only listens to local connections


6.How to access from an Android phone? (any program?)

Search play for vnc viewer.

eg. http://www.appbrain.com/app/android-vnc ... androidVNC
I don't think this supports ssh though.


Using both vnc and X11 the application runs on the remote computer. It's just the GUI that is sent over the network for local viewing.

ghans
Posts: 7883
Joined: Mon Dec 12, 2011 8:30 pm
Location: Germany

Re: remote access

Tue Oct 30, 2012 9:17 am

SSH is pretty safe. I'm not going to elaborate here , you can google more.
SSH can put an encrypted "envelope" around almost ANY protocol. This
is called SSH tunneling . penguintutor demonstrated
it for the X Windows and VNC protocol.


ghans
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