Remote Access Mac

Working from home using OS X 10.8 (Mountain Lion) or higher (by Jason Yang)

Pre-requisite for Mac

Before you continue, you must first make sure that your Mac has a correct hostname.

Run this command in a command window:

hostname

Make sure the hostname does not contain spaces or Chinese characters.

If your hostname contains space(s) or Chinese characters, do the following to fix it first:

Under Settings → Sharing

change the computer name (use a name with ONLY English letters and no spaces !)

XQuartz

You must first download and install the XQuartz app.

(That's because Apple has removed X11: click here)

XQuartz (commonly referred to as X11.app) is Apple Inc.'s version of the X server, a component of the X Window System, for Mac OS X.

Wikipedia: click here

Steps to download, install and run XQuartz

Step 1: download XQuartz from:
- http://xquartz.macosforge.org/landing/or
- http://xquartz.macosforge.org
Step 2: Install XQuartz app on your mac.
(Double click on the package icon in your Download folder and follow the instructions)
Step 3:Open the XQuartz app on your mac.
(By either finding the XQuartz app in your dashboard, or search it using the search (magnifying glass) app on the right corner of your desktop: ).
When you have opened XQuartz, an xterm window will automatically be open.
If there is no xterm window, please open one yourself by right clicking on the XQuartz icon on the dock, then chooseapplication → Terminal:

Important note:

You must use the XQuartz application to run "ssh" (see below) to connect to Emory.
(You cannot use an ordinary command window - it will not work)
If your Mac has been powered down, you may need to restart the XQuartz application.

External resource on XQuartz

I found an external source with information to install XQuartz: click here
(you can use it as additional info if the steps above are insufficient)

Connecting to Emory

Remote login to a workstation in the MathCS lab:

Open an xterm on your Mac.

Type the following command in the xterm window:

ssh -Y -l NetID lab0z.mathcs.emory.edu
        
Note:  0. Cut and paste the command to your MAC !!!
       1. Replace NetID with your Emory Net ID
       2. Must use: capital -Y and low case -l (ell) !!!!

Note:

Sometimes, -Y does not work and you will need:

ssh -X -l NetID lab0z.mathcs.emory.edu

worked better for them. Try -X (capital X) if -Y does not work.

(In either case, you must replace "NetID" with your Emory Net ID).

Log in with your password.
Note: you will not see anything that you typed (because the password is secret); however, letters are being entered until you hit the [Enter] key.
Important note: Do not compile and run your programs on lab0z.mathcs.emory.edu !!!

Very important:

After log in to lab0z.mathcs.emory.edu, check for unused machines in the MathCS lab with the command:

cat /tmp/labmachines

Example:

Select an unused machine from the list and use ssh to login to the lab machine:

ssh -X labUV         
Note:
On lab0z, you MUST use -X (and never use -Y, this is NOT a Mac) !!!

where:

U is a number: 1,2,3,4,5,6,7 V is a letter: a,b,c,d,e,f,g

Example:

ssh -X lab3d

(You may need to re-enter your Emory NetID password)

Then:

Use the cd command to change the working directory to your project directory

You are ready to work from your dorm !!!

Happy Tele-commuting !!!

After a successful connect, you can do anything from your dorm as if you were in the lab - well, things are just slower.

(I heard that the speed in the dorm is great; but if you have DSL or Cable, graphical applications - like EGTAPI can be a bit slow)

Open more windows on a lab machine

Opening more windows:

Note:

Only open more windows on an ordinary lab machine
Do not open more windows on lab0z.mathcs.emory.edu !!!

To open more terminals, type:

gnome-terminal &

Trouble Shooting

1. ssh_exchange_identification error

When you execute the ssh command, it exits right away with this error message:

Symptom:

OnYourMac>> ssh -X -l NetID lab0z.mathcs.emory.edu       
ssh_exchange_identification: read: Connection reset by peer

How to fix it:

You need to install Emory VPN !!!

See this link on how to install Emory VPN: click here

2. X_forwarding_request: XAuthorization error

When you execute the ssh command, it exits right away with the XAuthorization error message:

Symptom:

OnYourMac>> ssh -X -l NetID lab0z.mathcs.emory.edu       
X_forwarding_request: XAuthorization error

How to fix it:

Execute this command on your Mac:

rm ~/.Xauthority

Then try to connect to lab0z with the "ssh" command above.

3. X_request_forwarding: bad authentication data: MIT-MAGIC-COOKIE-1

When you execute the ssh command, it exits right away with the above error message:

Symptom:

OnYourMac>> ssh -X -l NetID lab0z.mathcs.emory.edu       
X_request_forwarding: bad authentication data: MIT-MAGIC-COOKIE-1

How to fix it:

Execute this command on your Mac:

rm ~/.Xauthority

Then try to connect to lab0z with the "ssh" command above.

4. Cannot make a connection to lab0z.mathcs.emory.edu

When you execute the ssh command, it exits right away:

Symptom:

OnYourMac>> ssh -X -l NetID lab0z.mathcs.emory.edu       
ssh_exchange_identification: read: Connection reset by peer

After running the ssh command, it exits with an error message.

Solution procedure:

Double click Macintosh HD on your Desktop.
On the left side of the box, under Places, click on your user name. This will take you to your home folder.
At your home folder, hit this key combination (All keys at once):
<command> + <shift> + <g>
A "Go to the folder:" box will pop up. Type .ssh in the box then hit <return>. This will take you inside the .ssh directory.
Delete the known_hosts file. Now you can use ssh again.

Further note:

If the above procedure does not work, then the MathCS firewall restrictions is blocking your access to lab0z.mathcs.emory.edu.

You must install Emory's VPN software:

Call LITS Helpdesk at 404-727-7777 and request access to the VPN for your NetID.
Following instructions at this webpage to install VPN software:
http://it.emory.edu/security/vpn.html

5. Cannot open new windows on a lab machine

You can logon to a lab machine. But you cannot open any new windows.

Symptoms:

You can login to lab0z.mathcs.emory.edu
You can login to a normal lab machine, let's say: lab1a.mathcs.emory.edu
On lab1a.mathcs.emory.edu, you cannot open any new windows

Solution procedure:

Open an xterm on your Mac.
Type the following command in the xterm window:
```
xlogo
```
Result:
If you got an error:
Fix:
You forgot to start the XQuartz application !!!!
If you see a window with a large X symbol:
Continue to step 3....
Type the following command in the xterm window:
```
ssh -X -l yourNetID lab0z.mathcs.emory.edu
```
Login to lab0z.mathcs.emory.edu and type this command:
```
lab0z% echo $DISPLAY
```
If the command echo $DISPLAY returns a value similar to "localhost:15.0", then:
run the following command:
```
xlogo
```
you should see a window with a large letter X.
If you see all the above, then:
Continue to step 4....
Otherwise, use this solution procedure:
- Go back to your Mac
- Edit this file: /etc/sshd_config
- Find these lines:
```
X11forwarding ...   X11DisplayOffset ...    X11localhost ...
```
  Make sure they are:
```
X11forwarding yes   X11DisplayOffset 10     X11localhost yes
```
  without a # preceding them !!!!
- Save the file /etc/sshd_config
- Reboot your Mac !!!
  After rebooting, try to connect to Emory (lab0z.mathcs.emory.edu) using the instructions above.
Type the following command on lab0z.mathcs.emory.edu:
```
lab0z: ssh -X lab1a.mathcs.emory.edu
```
(If ssh -X lab1a.mathcs.emory.edu is unavailable, use another workstation in the lab, e.g., lab3d.mathcs.emory.edu)
On lab1a type:
```
lab1a: xlogo
```
You should see a window with a large X.
If you don't see it, send an email to:
help@mathcs.emory.edu
and ask for help.

6. Fixing "REMOTE HOST IDENTIFICATION HAS CHANGED" error

Sometime, the MathCS department changes system information on the workstations (e.g.: upgrading to a new system).

This will cause the following error when you use ssh to connect to the machine:

@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
@    WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED!     @  
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  
IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!  
Someone could be eavesdropping on you right now (man-in-the-middle attack)!    
It is also possible that the RSA host key has just been changed.  
The fingerprint for the RSA key sent by the remote host is  
??:??:.... (a lot of numbers and letters separated by ":")  
Please contact your system administrator.

There is no attack, but you do need to fix something on your Mac before you can use ssh again...

How to fix it:

Double click Macintosh HD on your Desktop.
On the left side of the box, under Places, click on your user name. This will take you to your home folder.
At your home folder, hit this key combination (All keys at once):
<command> + <shift> + <g>
A "Go to the folder:" box will pop up. Type .ssh in the box then hit <return>. This will take you inside the .ssh directory.
Delete the known_hosts file. Now you can use ssh again.

Remote Access Mac

Working from home using OS X 10.8 (Mountain Lion) or higher (by Jason Yang)

Pre-requisite for Mac

XQuartz

Steps to download, install and run XQuartz

Important note:

External resource on XQuartz

Connecting to Emory

Note:

Very important:

You are ready to work from your dorm !!!

Happy Tele-commuting !!!

Open more windows on a lab machine

Note:

Trouble Shooting

Further note:

About

Department of Computer Science