This is a series of exercises that will walk you through the basic tasks as you get on board the Atos HPCF.

Prerequisites

In order to follow this tutorial, these are the prerequisites you must fulfil before starting:

• You must have a valid ECMWF account with privileges to access HPCF or ECS. If you only have access to ECS, you may need to skip certain exercises involving HPCF.
• You must have 2 Factor Authentication enabled with TOTP.
• You must be able to connect with at least one of the following methods:
  • Using the Virtual Desktop Infrastructure (VDI). See the corresponding documentation to get started.
  • Using Teleport SSH from your end user device .

Logging into Atos HPCF and ECS

First steps into Atos HPCF and ECS

First of all, let's try to connect to the computing services via SSH:

1. Access the default login node of the ATOS HPCF or ECS and take note of what node you are in 

   Solution - HPCF

   ssh hpc-login
   hostname

   Solution - ECS

   ssh ecs-login
   hostname

2. Open a new tab in your terminal and connect again. Did you get the same hostname? Why is that?

   Answer

   hpc-login hostname is an alias to a load-balanced service of login nodes. You may land on a different one every time you connect.

   ecs-login is an alias to a specific login node of the ECS virtual cluster, which may be changed

   Both aliases will always point to a working login node, and the actual node and complex behind it may change depending on the load, system sessions or outages.

3. Now, from your open SSH session on Atos HPCF or ECS, connect to the main login alias again. Did it ask for a password? Can you set your account up so jumps between hosts are done without a password?

   Answer

   Password-less SSH between ECMWF hosts such as Atos HPCF or ECS nodes, or VDI hosts is not set up by default. If you were asked for a password, you can run the following command from your Atos HPCF, ECS or VDI session to set up  key-based authentication:

   ssh-key-setup

   After this you should be able to jump between hosts without having to introduce your password.

   Besides being convenient, this setup is also necessary for other tools such as ECACCESS or ecinteractive to work properly.