# Connect from your personal computer to another computer

This is a typical user case when we need to work with a computer server to perform data analysis etc but not physically in front of the machine. Rather we connect to it from another machine, say a personal laptop.

Here we introduce in brief a few methods to connect and work with remote computers. I’ll call it “host” for the remote computer, and “guest” for the computer through which you connect to the host.

## Through command shell for Linux and Mac

First, obtain the IP address or domain name of the host computer. You may either be provided with the information, or you can run in command terminal (for a Linux host):

sudo ifconfig


to see the IP address. For example:

$sudo ifconfig eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.0.105 netmask 255.255.255.0 broadcast 192.168.0.255 inet6 fe80::ae1f:6bff:fe11:ab10 prefixlen 64 scopeid 0x20<link> ether ac:1f:6b:11:ab:10 txqueuelen 1000 (Ethernet) RX packets 123292 bytes 105881116 (100.9 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 130328 bytes 41654696 (39.7 MiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device memory 0xc7200000-c727ffff eth1: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 ether ac:1f:6b:11:ab:11 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device memory 0xc7100000-c717ffff  The information you should be looking at is the inet property under eth0, which in our case is 192.168.0.105 (this is the IP address in my local network domain). ### Connect via SSH On the guest computer, type ssh username@192.168.0.105  where username is the account name you have on the host machine. Please replace 192.168.0.105 with your IP address. If it fails, it might be possible that your host machine does not support SSH access. In that case you need to install SSH server on your host. For a Debian / Ubuntu host: sudo apt-get install openssh-server  If you want to be able to use graphical interface for apps on your host, for example use firefox to browse internet from host, you need to connect through -X option, eg, ssh -X username@192.168.0.105  #### Create a user on the host machine If you do not have a user account on the host, ask whoever administrates that machine to create one for you. He / she can use the command below: username=hxl group=docker # another option is www-data group, for a web server cd /home sudo useradd -g$group $username -d /home/$username -m -s /bin/bash
sudo passwd $username sudo cp .bash_profile .bash_prompt /home/$username
sudo echo 'export LC_ALL="en_US.UTF-8"' >> /home/$username/.bashrc sudo chown$username.$group -R /home/$username


You’ll be prompt to enter password. This will add user hxl to docker group.

Notice the line cp .bash_profile .bash_prompt /home/\$username – I put a couple of template configuration files under /home folder to copy to a new account. This will make the terminal prompt look better.

## Through command shell for Windows 10

Windows 10 users can install the WSL program to have a Linux subsystem on their Windows computer. Then can connect following the same steps as above for Linux users.

## Through JupyterLab

### Install JupyterLab on host

If you are a JupyterLab user you probably already have JupyterLab running on the host, or at least knows how to install it. If not, this page contains the commands to set it up.

### If the host is a regular desktop computer

#### Start JupyterLab server on host

First you need to connect to the host via SSH. Please open a new terminal to connect. Details see section above.

Once you are connected to host, type this line:

jupyter-lab --no-browser &


You should see lots of output. Of relevance is some lines like this:

[C 12:40:51.496 LabApp]

Copy/paste this URL into your browser when you connect for the first time,
http://localhost:8888/?token=1a90c5465f3295c8354a6e2365b961e88affb880559f51cb


Once you see it you know the JupyterLab server is up and running (on the background on the remote host). There are two important piece of information you need to keep:

1. The port number the JupyterLab server is to be accessed: 8888
2. The token (password): 1a90c5465f3295c8354a6e2365b961e88affb880559f51cb

The port number and token can be different every time you connect.

At this point you can hit enter key to bring yourself back to the terminal, then type exit to quit the host. It is very important to quit properly!

#### Connect to host JupyterLab from guest

ssh -NL 1828:localhost:8888 username@192.168.0.105


where:

1. 8888 is the port number you see in the previous step on the host. Replace it with what you actually see.
2. username is your username on the host, replace it with your username
3. 192.168.0.105 is my host IP address, see previous section on SSH connections. Replace it with the actual IP of your host computer.
4. 1828 is a port number you assign on your guest machine to map to host JupyterLab server port. It can be a random number like this, or like 2888, 3888, 6666 as long is they are not being used by other apps on your computer. Just type in any 4-digits number. The command will complain and fail if the port you choose is not available.

Hit enter, you might be asked to enter password. After that, nothing will show up. Do not worry it is a good sign! Now in your web browser type http://localhost:1828 you should be directed to the page where you get asked the token and you input that using the token generated above.

### If the host is a cluster system

At least for University of Chicago clusters we can connect to a compute node on it directly using SSH tunnel. We can run JupyterLab on compute nodes and connect to it directly via SSH tunnel, along the lines of this post. It does not involve running anything on the login node.

This script works for UChicago RCC midway HPC. Here are instructions.

### Use command terminal from within JupyterLab

The “Launcher” page of JupyterLab has a few types of items to launch:

• Notebook
• Console
• Terminal

We typically launch a Notebook, but the other two are also very useful. For example to get yourself a conventional command terminal you just click on Terminal then you’ll be brought to the command terminal. You can also try to create a Bash Console. It is like something in between terminal and notebook. Sometimes you might find it more user-friendly.

## Through vscode

vscode is my text editor of choice. I use this extension to connect to remote computer. Workspace configuration example:

{
"folders": [{
"uri": "sftp://gaow:statgen@205.208.52.221/home/gaow",
"name": "My office computer"
}]
}


## Through Rstudio server

Access to Rstudo server, as documented on this page, is very straightforward once Rstudio server is installed. Notice that the URL needs to be http:// and not https://.