Connecting to the cluster
The Zaratan HPC cluster has several login nodes which you can access through the SSH protocol. Accessing the cluster also requires Multi-Factor Authentication (MFA). You can satisfy the MFA requirement by logging into the university VPN (which requires MFA) or by entering DUO push/phone call/passcode every time you SSH into the login nodes. We recommend using the GlobalProtect VPN before you initiate an SSH session. We also recommend you register multiple devices for DUO and have a list of one-time passcodes as a backup. See DIT knowledge base articles for details about MFA/DUO.
The username and the passphrase you use for the HPC cluster are the same ones you use to access the UMD email system and other university-wide systems.
SSH login basics
- Username: University Directory ID
- Password: University passphrase
- Remote hostname:
login.zaratan.umd.edu
Zaratan login node SSH key fingerprints
The first time you connect to login.zaratan.umd.edu, your SSH client
needs to verify the authenticity of the remote host. The client will show
you the server's (Zaratan login nodes') key fingerprint. You must
verify that it matches one of the following keys before you accept
and continue. (DSA, RSA, ECDSA and ED25519 are various cryptographic
algorithms used to generate the SSH keys on the server side. MD5 and
SHA256 are the fingerprint hashes.)
Zaratan login nodes' SSH key fingerprints
DSA MD5: 18:44:38:42:fb:f5:b9:e7:a0:07:9a:b1:5a:cc:5e:82
DSA SHA256: 9BISdMgfLdqjR1GmFFam1WKpOrdhlEpsxquCG1jlQDg
ECDSA MD5: 28:2c:bf:74:75:d5:62:65:84:74:f2:0f:a8:ff:fe:12
ECDSA SHA256: XGCCZxapg+RqECPFMhTfRci09sJlsKyhY/CtoTq2R8k
ED25519 MD5: 4e:41:a6:07:3f:f6:a1:12:fc:01:6b:c6:42:de:18:4e
ED25519 SHA256: Ot4bTjdmv3t8Lwn2uETVlAFPzhFoQafQ7tt+oHAN69w
RSA MD5: e8:41:71:ac:fc:4c:08:c7:bc:0f:f0:33:95:5b:c4:e0
RSA SHA256: tHrtumZ7yW/Ucnm/mPGcpWfIaRVO/FccsheoWDv6MWM
Once you accept the key, your SSH client will cache it locally and use it to verify the authenticity of the remote host in subsequent SSH attempts. That's why it is important that you verify the fingerprint the first time you connect to a remote host. See the FAQ SSH remote host identification warning to know what to do if you encounter a fingerprint mismatch.
SSH clients for your machine
The exact SSH client software you need depends on your Operating System.
SSH clients for Windows
-
PuTTY is a reliable application that has been around for a long time. This is a third-party application you'd have to download and install. Here are some PuTTY tutorials and how-tos.
-
MobaXterm is a modern application that combines an SSH client, X11 server, network tools and more. This is a third-party application which you'd have to download and install.
-
Windows Terminal and OpenSSH are installed by default (or at least available via "Features On Demand") on modern Windows OSes.
SSH clients for macOS and Linux
- OpenSSH and the Terminal applications are available by default.
SSH Command-Line examples
As shown above, all three major OSes have a Terminal app and OpenSSH.
In the following examples, please replace <USERNAME> with your
own UMD dirID.
Example
There are multiple nodes behind login.zaratan.umd.edu. Let's
pick one at random:
ssh <USERNAME>@login.zaratan.umd.edu
ssh -l <USERNAME> login.zaratan.umd.edu
In other cases, you may wish to connect to a specific login node.
(For instance, you may have left a screen or tmux sessions on
one of the nodes.)
ssh <USERNAME>@login-1.zaratan.umd.edu
ssh -l <USERNAME> login-2.zaratan.umd.edu
SSH Warning: Remote host identification has changed
If you receive a warning message similar to the following, it means that there is a mismatch between the key fingerprint your client has cached and that of the server. (This is why it is important that you cache the correct key fingerprint in your first SSH attempt. See "Zaratan login node SSH key fingerprints" at the top of this page.)
Do not ignore this warning. There is a possibility of a man-in-the-middle attack. Do not enter your university credentials. Please contact the systems staff.
SSH Warning
@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@
@ 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
5c:9b:16:56:a6:cd:11:10:3a:cd:1b:a2:91:cd:e5:1c.
Please contact your system administrator.
Linux CLI
When you are successful in SSH-ing to one of the Zaratan login nodes,
you will end up on a Linux CLI bash shell as the example below shows.
The prompt will show you the hostname of whichever login node you connected to,
the current working directory (in this case the ~ refers to your home
directory), and $ signifying the end of the prompt.
Example
login-1:~$
login-2:~$
You are now at a point where you can try some Linux commands.
Responsible use
Please note that the login nodes are a shared resource. There may be many other cluster users who are currently logged in on the same node. Your actions may impact their ability get their work done. So it is important that we remind you of the following:
WARNING: Login node usage
DO NOT RUN computationally intensive processes on the login nodes. Doing so is against the HPC cluster usage policies. Such processes will be terminated without warning. Repeated offenses can lead to suspension of your privilege to use the clusters.