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guide:connect

Connecting to the CHPC

The CHPC hosts a supercomputer comprising:

  • 1008 regular compute nodes with 24 cores and 128 GiB of RAM each; and
  • 5 large memory nodes with 56 cores 1TiB of RAM each

The cluster will be augmented in the future with:

  • a GPU-powered visualisation node; and
  • other specialised servers

Host Name

All these systems are accessed via a single login node: lengau.chpc.ac.za.

Logging In

Connection to the login node of the CHPC cluster is via the ssh protocol. To connect to the system use

  ssh username@lengau.chpc.ac.za

where username is replaced by the user name assigned to your account at the CHPC.

Transferring Files

Use scp or sftp to transfer files to or from your home directory on the CHPC systems. For example

  scp src.tar.gz username@scp.chpc.ac.za:~/scratch/

to copy the file src.tar.gz to your scratch directory on the CHPC cluster. If you would like a more user-friendly method, consider FileZilla

Note: use scp.chpc.ac.za as the server when transferring files.

Dedicated scp.chpc.ac.za

A dedicated node, scp.chpc.ac.za will become available for large or long-running transfers:

  scp src.tar.gz username@scp.chpc.ac.za:~/scratch/

Recommended: ssh keys

The best way to connect via ssh is to create ssh keys which authenticate you instead of your password.

First create your private and public keys on your main work computer. These steps assume that is a desktop or laptop computer running Linux:

  ssh-keygen -t dsa

This creates two new files in your .ssh directory

id_dsa your private key
id_dsa.pub the corresponding public key

It is the latter file that you need to add to the .ssh/authorized_keys file in your home directory on the CHPC login node.

From a recent Linux distribution you can simply do this :-

  ssh-copy-id username@lengau.chpc.ac.za

From older Unix setups you might have to do this :-

  cat ~/.ssh/id_dsa.pub | ssh username@lengau.chpc.ac.za "cat >> .ssh/authorized_keys; chmod 0700 .ssh; chmod 0600 .ssh/authorized_keys"

And the next time you ssh or scp to the CHPC login node you won't have to use your password!

NOTE: ssh FILE PERMISSIONS

Notice that you need to change the permissions of the .ssh directory and the authorized_keys file on the login nodes to make them private and readable by you only before ssh will use the new public key.

chmod -R g-rwx,o-rwx ~/.ssh

You also need to make sure your home directory does not have write w enabled for group and other fields.

ls -ld ~
drwxr-xr-x 19 user user 4096 Aug 15 12:01 /home/user

which is done with

chmod 0750 ~

to make your entire home directory private; or

chmod 0755 ~

to allow other users to view your files.

Connecting from MS Windows

Cygwin

Cygwin provides all the above Linux commands for the Windows command line (and replaces the limited CMD.EXE command line).

For first-timers there is a nice introduction at lifehacker.

MS Windows Applications

Should you prefer a MS Windows application with a GUI to connect to the CHPC we suggest you download and install the open source PuTTY and WinSCP clients, or alternatively MobaXterm, which has a free “home” edition.

Windows Application Provides Home page
PuTTY ssh http://www.chiark.greenend.org.uk/~sgtatham/putty/ download
WinSCP scp/sftp http://winscp.net/ download
MobaXterm ssh/scp/X-Forwarding http://mobaxterm.mobatek.net http://mobaxterm.mobatek.net/download-home-edition.html
Git Bash Whole unix environment including ssh https://git-scm.com https://git-scm.com/download/win

ssh keys

It is strongly recommended that you use ssh keys to connect to the CHPC. To generate and configure putty-ssh to use keys please see:

To generate and configure Git to use ssh keys please see:

Blocked User Accounts

It may be that your account is blocked because of multiple failed logins. Check if that is so via https://users.chpc.ac.za/reports/ip_check/

It is important to note that if you had more than 6 failed login attempts, your account will be blocked and either you will have to log a call on https://users.chpc.ac.za/helpdesk or wait for 30 minutes before trying to login again. However if you wait for 30 minutes and try once again with an incorrect password, you will be locked for another 30 minutes until you login with a correct password where your username will be removed from the blocked list. Only then you will regain your 6 grace failed login attempts.

/var/www/wiki/data/pages/guide/connect.txt · Last modified: 2018/08/15 14:59 by wikiadmin