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Institute for Advanced Simulation (IAS)

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Access/Environment

Dispatch

Prerequisite for using the Juelich Supercomputer systems is to successfully pass through the application process. A special request for a JUDAC account is not necessary because the access to JUDAC is granted for all Juelich Supercomputer users automatically.

Login Procedure

Users can't login by suppling username/password credentials. Instead password free login based on SSH key exchange has been set up for the authentification process.

The public SSH key has to be generated on the workstation the user uses to access JUDAC. The key can be generated by executing e.g. in Linux

ssh-keygen -t [dsa|rsa]

It is required to protect the SSH key with a non-trivial pass phrase to fulfill the FZJ security policies. (For further details on SSH key generation see FAQ: How to generate ssh keys)

The contents of the public key file file id_dsa.pub or id_rsa.pub must be uploaded through the WEB interface when initially applying for an userid. It will overwrite $HOME/.ssh/authorized_keys anyway, either during the creation of the Supercomputer account or when sendig a new key.


Note: Make sure there is no write access for group or world on the $HOME directory nor on the .ssh directory. Otherwise SSH does not work.
In case your SSH key became unavailable for an existing account, please use the dispatch ssh-key upload page, to initiate the installation of a new key.


After that a typical login looks like

ssh <userid>@judac.fz-juelich.de

Login Environment

Shell

The Login Shell on each system points to system's favored shell: JUDAC -> bash
Users are not allowed to change the Login Shell, but they can switch to a personal shell within the login process. User's will find a template within the initial FZJ .bashrc in $HOME.

Home directory ($HOME)

Home directories reside on a GPFS file system. In order to hide the details of the home file system layout the full path to the home directory of each user is stored in the shell environment variable $HOME. References to files in the home directory should always be made through the $HOME environment variable. The initialization of $HOME will be performed during the login process.

Other file systems

Other important storage locations are the scratch file system ($WORK), and the archive file systems ($ARCH). The following table summarizes the information:

VariableStorage LocationDescription
$HOMEGPFS filesystemUser's home directory
$WORKGPFS filesystemUser's storage location for fast scratch
$ARCHGPFS filesystemUser's storage location for archiving

It is highly recommended to access files always with the help of these variables. The values of these variables are automatically set during login.


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