> For the complete documentation index, see [llms.txt](https://compsci-hunter.gitbook.io/xie-research-group/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://compsci-hunter.gitbook.io/xie-research-group/hpc-environments/hpc-user-guide/connecting-to-hpcs.md).

# Connect to HPCs

The IP addresses of the HPCs are:

| HPC    | IP address/Host name    |
| ------ | ----------------------- |
| DGX    | 146.95.214.135          |
| DLS    | 146.95.128.169          |
| Dragon | csgpu01.hunter.cuny.edu |

All of the machines are inside the network of Hunter College (Hunter network).

## 1. Inside the Hunter Network

You can use `ssh` via a computer inside the Hunter network to access it:

```
ssh yourname@IPaddress
```

## 2. Outside the Hunter Network

If you want to access the HPCs outside the Hunter network, you can use the following two ways:

### 2.1. SSH with Username and Password

1. Use `ssh` to connect to eniac from anywhere using your [eniac account](http://web.archive.org/web/20190726111206/http://www.geography.hunter.cuny.edu/tbw/CS.Linux.Lab.FAQ/department_of_computer_science.faq.htm):

   ```bash
   ssh username@eniac.cs.hunter.cuny.edu
   ```

   (Note: To apply for a new eniac account or reset your password, just send an email to <cstechsp@hunter.cuny.edu> with your Hunter email address)
2. After connecting to eniac, use `ssh` to connect to the HPCs:

   ```bash
   ssh username@IPaddress
   ```

### 2.2. SSH with SSH Key Pair (Recommended)

This way is more secure than the first one and you don't need to type your password every time. You will still need an [eniac account](http://web.archive.org/web/20190726111206/http://www.geography.hunter.cuny.edu/tbw/CS.Linux.Lab.FAQ/department_of_computer_science.faq.htm).

1. Create your own SSH keys

   **MacOS/Linux:**

   ```bash
   ssh-keygen
   ```

   Hit enter to keep the default settings all the way until the key pair is successfully created.

   **Windows:**\
   Windows now supports OpenSSH. If `ssh` command does not work, you should be able to install it following the instructions here: [OpenSSH in Windows](https://docs.microsoft.com/en-us/windows-server/administration/openssh/openssh_overview). The following protocols are based on OpenSSH. You should also be able to do it with PuTTY, but it is not recommended.
2. Copy your public key to eniac and HPCs

   After generating the SSH key pair, you should get two files in your local `.ssh` directory: `id_rsa` and `id_rsa.pub`. `id_rsa` is your private key, you should keep it only to yourself. The `id_rsa.pub` file is the public key file. We need to copy it to eniac and HPCs so we do not need to type password every time. The command to copy your `id_rsa.pub` to another computer is:

   ```bash
   ssh-copy-id -i ~/.ssh/id_rsa.pub (path to your local id_rsa.pub) user@host
   ```

   The copying will ask for your password. You need to copy your public key to eniac first and connect to eniac with `ssh`, copy the same key to HPCs again. Now you should be able to connect to eniac with

   ```bash
   ssh username@eniac.cs.hunter.cuny.edu
   ```

   without being asked for passwords.
3. Set up the SSH config file

   Setting up an SSH config file will let you connect to HPCs from your local machine with only one line of command without complex URLs or IP addresses. First, you need to create a file named `config` in your local `.ssh` folder. In the file, put the following example contents:

   ```bash
   Host jump-box
      HostName eniac.cs.hunter.cuny.edu
      User eniac_username
      IdentityFile ~/.ssh/id_rsa (path to your local id_rsa)
      ServerAliveInterval 240

   Host dgx
      HostName 146.95.214.135
      User dgx_username
      IdentityFile ~/.ssh/id_rsa (path to your local id_rsa)
      ProxyCommand ssh -q -W %h:%p jump-box
      ServerAliveInterval 240

   Host dls
      HostName 146.95.128.169
      User dls_username
      IdentityFile ~/.ssh/id_rsa (path to your local id_rsa)
      ProxyCommand ssh -q -W %h:%p jump-box
      ServerAliveInterval 240
   ```

   The first code block defines a proxy host. In our case, it is the eniac server. The second and third code blocks are for DGX and DLS, respectively. In the case of Windows, if the ProxyCommand causes errors, you can try to replace the `ssh` with the full path to `ssh.exe` file. For example, in my case, the ProxyCommand is:

   ```bash
   ProxyCommand C:\\Windows\\System32\\OpenSSH\\ssh.exe -q -W %h:%p jump-box
   ```

   ServerAliveInterval variable lets your terminal send an empty package to the server every x seconds to keep your connection alive. With the config file, you should be able to connect to HPCs simply with:

   ```bash
   ssh dgx
   ```

   or

   ```bash
   ssh dls
   ```

   You should also be able to use `scp` command below:

   ```
   scp local/file.txt dgx:/raid/home/username/...
   ```