Connection to interactive servers

CC-IN2P3 provides any user having a computing account with two interactive clusters accessible with the following syntax:

cca clusterccahm cluster

% ssh -Y <username>@cca.in2p3.fr

The general-purpose cluster, it can be used to prepare the jobs before they are submitted to the computing platform: development, test, etc.

• cca.in2p3.fr and ccahm.in2p3.fr are aliases redirecting to the least loaded server of each cluster,

• the -Y option enables trusted X11 forwarding,

• for Microsoft Windows users we recommend the use of PuTTY as an SSH client.

Important

In case of connection error with SSH command,

• check on the Identity Management Portal that your account is still active,

• make sure your account is a computing account,

• if this is the case, send a ticket to user support with the output of the command in debug mode:

% ssh -vvv <username>@cca.in2p3.fr

• Using Visual Studio Code
  • Getting started
  • Troubleshooting

• Using VNC
  • Destination Ports

Best practices

As each interactive server is shared by multiple users, we recommend a number of good practices to follow so that your activities can coexist with the other users activities.

Attention

Non compliance with these rules may result in some of your processes termination.

• Only one computing process is allowed per interactive server and 3 processes over the entire interactive platform. Time restrictions apply:

  • 24 hours maximum CPU time for a process and 1 hour CPU time for a multi-core process,

  • inactive processes for more than 24 hours are killed.

• parallel processes with intensive use of both CPU and input/output are not allowed (example: make -j, scons, b2, ninja, etc.). However, it is possible to run such processes as interactive jobs (see interactive jobs),

• avoid excessive memory consumption that could have an impact on the system, if large memory usage is required, please switch to the ccahm cluster . The command htop -u username may be a useful monitoring tool,

• it is forbidden to run tasks in “batch” mode (eg: processing a large amount of files in loop),

• /scratch is not a permanent storage space: data can be deleted at any time to free up space. Under normal circumstances data is deleted after 14 days. Also, avoid large data storage,

• One transfer process is allowed per server (example: scp, rsync or dq2-get) and 3 processes across all interactive servers,

• Detached and persistent processes after logout are not allowed.

  • Screen may be an exception to this rule, but it is neither meant as a substitute to the batch system, or as a way to run services nor as a way to hog scarse resources (like GPU interactive computing nodes),

  • the case of Visual Studio Code is explained in the dedicated paragraph.

• To preserve user data confidentiality, rmate (or other similar editor) requires using a random TCP port instead of a fixed port.

Data transfer

Only the SSH protocol is allowed for connections and file transfers to or from the CC-IN3P3 interactive servers. Two authentication modes are preferred: using password, or Kerberos ticket (via GSS-API). An RSA/DSA type authentication (SSH key) will grant you access, but will not initialize your Kerberos ticket.

To copy files:

% scp <my file> <username>@cca.in2p3.fr:~/<my directory>/

% sftp <username>@cca.in2p3.fr

For more information, please refer to the above commands manual pages (man <command>).

Note

For remote management of your data (synchronization, backup, etc.), CC-IN2P3 provides the RClone software solution. Please refer to the dedicated pages.