Login to cluster

Here you will find information on how to connect to ALICE from Linux, Windows or MacOS.

To login to the ALICE cluster, you need to perform a hop-like login sequence. The login nodes of the ALICE cluster cannot be accessed directly. You will need to first log in to an ssh gateway (or jumphost) and then you can connect to one of the login nodes. This login mechanism is required for everything that you want to do on ALICE. However, there are ways to simplify the process which are described below.

Best Practices

Know when you are on a login node.  You can use your Linux prompt or the command hostname.  This will tell you the name of the login node that you are currently on. Note that the ssh gateway host itself is a secure portal from the outside and serves no compute function.

• Appropriate activities on the login nodes:
  1. Compile code, Developing applications,
  2. Defining and submitting your job,
  3. Post-processing and managing data,
  4. Monitoring running applications.
  5. Change your user password.

• Avoid computationally intensive activity on the login nodes.
  1. Don't run research applications.  Use an interactive session if running a job is not appropriate.
  2. Don't launch too many simultaneous processes.  While it is fine to compile on a login node, avoid using all of the resources. For example "make -j 14" will use half of the cores.
  3. That script you run to monitor job status several times a second should probably run every few minutes.
  4. I/O activity can slow the login node for everyone, like multiple copies or "ls -l" on directories with 000's of files.

• Hyperthreading is turned off.  Running multiple threads per core is generally not productive.  MKL is an exception to that if it is relevant to you.

Login to ALICE from Linux

SSH Gateway and login nodes

The ssh gateway is named:

ssh-gw.alice.universiteitleiden.nl (132.229.92.63)

The login nodes are named:

login1.alice.universiteitleiden.nl (10.161.0.12)
login2.alice.universiteitleiden.nl (10.162.0.13)

Setup ssh connection

Here, we describe how you can configure your ssh connection to connect to ALICE in the easiest possible way. We will use a feature called ProxyJump in OpenSSH which is available in OpenSSH versions 7.3 and higher. If you have an older version of OpenSSH please have a look at SSH tunneling for older versions of OpenSSH. You can find out the version of OpenSSH by typing ssh -V in your terminal.

In your Linux system open ~/.ssh/config in your favourite text editor (or create the file if it does not exist). Then add for instance

Host hpc1 
  HostName login1.alice.universiteitleiden.nl
  User <USERNAME>
  ProxyJump <USERNAME>@ssh-gw.alice.universiteitleiden.nl:22
  
Host hpc2
  HostName login2.alice.universiteitleiden.nl
  User <USERNAME>
  ProxyJump <USERNAME>@ssh-gw.alice.universiteitleiden.nl:22

(Replace <USERNAME> by your own ULCN account name.)

Add monitoring tools

If you want to look at the monitoring tools that are running on the management node too, you could add additional tunnelling commands to the config for a specific host. Do not add tunnels to all definitions as they may produce conflicts when you use the same tunnel twice. So add the tunnel commands, for instance, to one host like:

Host hpc1tunnel
  HostName login1.alice.universiteitleiden.nl
  User <USERNAME>
  ProxyJump <USERNAME>@ssh-gw.alice.universiteitleiden.nl:22
  LocalForward 8081 management.alice.universiteitleiden.nl:8081
  LocalForward 8080 management.alice.universiteitleiden.nl:443

SSH tunneling for older versions of OpenSSH

Alternatively, if your OpenSSH server isn't that recent (version 7.2 or earlier) and doesn't recognize the ProxyJump alias, try this:

Host hpc1 
  HostName login1.alice.universiteitleiden.nl
  User <USERNAME>
  ProxyCommand ssh -X <USERNAME>@ssh-gw.alice.universiteitleiden.nl -W %h:%p

Adding X11 fowarding

You can even set your ssh connection to automatic X11 forwarding by adding the following setting:

ForwardX11 yes

Direct login to login nodes

If you completed the above steps you should be able to login to one of the login nodes by simply typing this:

 ssh hpc1

You will be asked to provide your ALICE user password twice (not your ULCN or LUMC password), once for the ssh gateway and once of the login node. If you do this for the first time, you will also be asked to confirm the identity of the ssh gateway and the login node.

Password-less login using SSH keys

If you do not wish to enter you password everytime you login you can use ssh keys. If you have not yet used ssh keys before, please have a look at this page: Public key authentication from Linux

If you have an ssh key, you need to deposite it first on the ssh gateway and then on the login node. You can use ssh-copy-id to copy your public key from your local machine to the ssh gateway, e.g.,

ssh-copy-id -i ~/.ssh/id_rsa.pub <USERNAME>@ssh-gw.alice.universiteitleiden.nl

(use your ALICE password for this). This will put your public key in ~/.ssh/authorized_keys on the ssh gateway. Then login to the ssh gateway (ssh <USERNAME>@ssh-gw.alice.universiteitleiden.nl) to test it. If it works log out again and use ssh-copy-id to deposite the key on a login node using the ssh tunnel defined above.

ssh-copy-id -i ~/.ssh/id_rsa.pub hpc1

This will put your public key in ~/.ssh/authorized_keys in your HOME directory on the login node. Verify that this step has worked by logging in to the login node (ssh hpc1). It is sufficient to do this for only one login node. You will also be able to login to the other login node without entering your password now.

If all was setup correctly, you should be logged in to one of the login nodes without typing your password.

Accessing monitoring tools

Having set up the ssh tunneling required to access the monitoring tools on the cluster you are now able to access port 443 (general secure web server on the management node) and port 8081 (specific port in use by the Bright Cluster Manager monitoring tools).

So in a browser, you could type:

https://localhost:8080

to gain access to the management main web server, or you could type:

https://localhost:8081/userportal

to gain access to the Bright Cluster Manager User Portal.

Login to ALICE from Windows

There are multiple ways to connect to ALICE from Windows. Below a list in order of complexity using:

Login to ALICE from MAC OS

Logging in with a Mac requires no extra installation on your local machine.

• Under “File”, open a new finder window. Navigate to the “Applications” folder, then the “Utilities” folder. Open a terminal window.

• Edit your ~/.bash_profile to incorporate:

   export LC_ALL=en_US.UTF-8
   export LANG=en_US.UTF-8 

• Open a new tab to make sure these settings are in effect (Shell -> New Tab).

• Edit your ~/.ssh/config file and put in:

Host hpc1 
  HostName login1.alice.universiteitleiden.nl
  User <USERNAME>
  ProxyJump <USERNAME>@ssh-gw.alice.universiteitleiden.nl:22

(Replace <USERNAME> by your own ULCN account name.)

Now you can login to the ALICE login 1 node by typing on the command line:

ssh hpc1

All other settings are similar to the Linux login setup