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Connecting via SSH on Unix

Hint

Please read the pre-requisites. Especially pay attention to the username.

Activating your Key in the SSH Key Agent

Activate the key (if this is your first SSH key then it will be enabled by default) by making sure ssh-agent runs in the background

# eval "$(ssh-agent -s)"

and adding the key

# ssh-add

or if you created another key, specify the file name, e.g. ~/.ssh/mdc_id_rsa

# ssh-add ~/.ssh/mdc_id_rsa

MacOS

If you run into problems that your key is not accepted when connecting from MacOS, please use:

# ssh-add --apple-use-keychain

Connect to the cluster

If you are within BIH, Charite or the MDC, then one of the following commands should work now (<USERNAME> is the cluster username). This will connect you to the login node.

# ssh -A -t -l <USERNAME> hpc-login-1.cubi.bihealth.org
  • <X> can be either 1 or 2
  • Use hpc-transfer-<X> instead of hpc-login-<X>.cubi.bihealth.org for file transfers!

Warning

Do not perform any computation on the login nodes

Connecting from outside of MDC network (for MDC Users only)

Danger

If you are outside of MDC or CUBI then use the following two commands to first connect from your client to the SSH gateway (ssh1 aka jail1) and then connect to the login node. Charite users have no possibility to connect from outside. Note that for logging into the jail, the <MDC_USER> is required.

Make sure to add your key, otherwise the forwarding does not work:

$ ssh-add

Connect to the hop-node:

$ ssh -A -t -l <MDC_USER> ssh1.mdc-berlin.de
...
jail1 $ ssh -A -t -l <USERNAME> hpc-login-<X>.cubi.bihealth.org
  • <X> can be either 1 or 2

On the cluster, the following brings you to a cluster node where you can compute as much as the node can chew.

res-login-1:~$ srun --pty bash -i
med0124:~$

Connecting with another computer/laptop

If you need to connect to the cluster from another computer than the one that contains the SSH keys that you submitted for the cluster login, you have two possibilities.

  1. Generate another SSH key pair and submit the public part as described beforehand.
  2. Copy your private part of the SSH key (~/.ssh/id_rsa) to the second computer into the same location.

Danger

Do not leave the key on any USB stick. Delete it after file transfer. This is a sensible part of data. Make sure that the files are only readable for you.

$ cd ~/.ssh
$ chmod g-rwx id_rsa*
$ ssh-add  id_rsa

File System mount via sshfs

$ sshfs <USERNAME>@hpc-transfer-<X>.cubi.bihealth.org:/ <MOUNTPOINT>
  • <X> can be either 1 or 2
  • hpc-transfer-<X>:/ follows the structure <host>:<directory>; in our case it refers to the cluster root folder but can be any path available to you on the cluster and gives the folder that will be mounted.
  • <MOUNTPOINT> must be an empty but existing and readable directory on your local computer

On MacOS, make sure you have both OSXFUSE and SSHFS installed. You can get both from here: https://osxfuse.github.io/ or the most recent version via Homebrew: 

$ brew cask install osxfuse; brew install sshfs; brew link --overwrite sshfs
The last command is optional and unlinks any pre-existing links to older versions of sshfs. Now you can run 
$ sshfs -o follow_symlinks <USERNAME>@hpc-transfer-1<X>.cubi.bihealth.org:<directory_relative_to_Cluster_root> <MOUNTPOINT> -o volname=<BIH-FOLDER> -o allow_other,noapplexattr,noappledouble

Configure SSH Client

Add the following lines to your ~/.ssh/config file for more comfortable access to the cluster. Replace MDC_USER_NAME with your MDC user name.

Host bihcluster
    ForwardAgent yes
    ForwardX11 yes
    HostName hpc-login-1.cubi.bihealth.org
    User MDC_USER_NAME
    RequestTTY yes

Host bihcluster2
    ForwardAgent yes
    ForwardX11 yes
    HostName hpc-login-1.cubi.bihealth.org
    User MDC_USER_NAME
    RequestTTY yes

Now, you can do type the following (and you don't have to remember the IP of the login node any more).

$ ssh bihcluster

You can also chain the commands to directly execute srun after your SSH connection.

$ ssh bihcluster srun --pty bash
...
med0123 $

The configuration works for you inside CUBI or MDC. If you are located anywhere else, you can use the following ~/.ssh/config lines.

Host mdcjail
    ForwardAgent yes
    ForwardX11 yes
    HostName ssh1.mdc-berlin.de
    User MDC_USER_NAME
    RequestTTY yes

Now, do

# ssh mdcjail ssh -A -t -l MDC_USER hpc-login-<X>.cubi.bihealth.org
  • <X> can be either 1 or 2

X11

Do you really need to run a graphical application on the cluster?

Please note that running more complex Java applications, such as IGV may be not very efficient because of the connection speed. In most cases you can run them on your local workstation by mounting them via SSHFS.

Connect to one of the login nodes using X11 forwarding:

# ssh -X -C -A -t -l <USERNAME> hpc-login-<X>..bihealth.org
  • <X> can be either 1 or 2

Once you get a login prompt, you can use the srun command with the --x11 parameter to open a X11 session to a cluster node:

# srun --pty --x11 bash

And finally you can start your X11 application, e.g.: 

# xterm

After a while Visual Terminal should start:

Last update: September 1, 2023