shell-and-data-access.md

Accessing the Cluster

Shell Access

The Anselm cluster is accessed by SSH protocol via login nodes login1 and login2 at address anselm.it4i.cz. The login nodes may be addressed specifically, by prepending the login node name to the address.

Login address	Port	Protocol	Login node
anselm.it4i.cz	22	ssh	round-robin DNS record for login1 and login2
login1.anselm.it4i.cz	22	ssh	login1
login2.anselm.it4i.cz	22	ssh	login2

The authentication is by the private key

!!! note Please verify SSH fingerprints during the first logon. They are identical on all login nodes:

29:b3:f4:64:b0:73:f5:6f:a7:85:0f:e0:0d:be:76:bf (DSA)
d4:6f:5c:18:f4:3f:70:ef:bc:fc:cc:2b:fd:13:36:b7 (RSA)

Private key authentication:

On Linux or Mac, use

local $ ssh -i /path/to/id_rsa username@anselm.it4i.cz

If you see warning message "UNPROTECTED PRIVATE KEY FILE!", use this command to set lower permissions to private key file.

local $ chmod 600 /path/to/id_rsa

On Windows, use PuTTY ssh client.

After logging in, you will see the command prompt:

                                            _
                       /\                  | |
                      /  \   _ __  ___  ___| |_ __ ___
                     / /\ \ | '_ \/ __|/ _ \ | '_ ` _ \
                    / ____ \| | | \__ \  __/ | | | | | |
                   /_/    \_\_| |_|___/\___|_|_| |_| |_|


                        http://www.it4i.cz/?lang=en

Last login: Tue Jul  9 15:57:38 2013 from your-host.example.com
[username@login2.anselm ~]$

Example to the cluster login:

!!! Note "Note" The environment is not shared between login nodes, except for shared filesystems.

Data Transfer

Data in and out of the system may be transferred by the scp and sftp protocols. (Not available yet.) In case large volumes of data are transferred, use dedicated data mover node dm1.anselm.it4i.cz for increased performance.

Address	Port	Protocol
anselm.it4i.cz	22	scp, sftp
login1.anselm.it4i.cz	22	scp, sftp
login2.anselm.it4i.cz	22	scp, sftp
dm1.anselm.it4i.cz	22	scp, sftp

The authentication is by the private key

!!! Note "Note" Data transfer rates up to 160MB/s can be achieved with scp or sftp.

1TB may be transferred in 1:50h.

To achieve 160MB/s transfer rates, the end user must be connected by 10G line all the way to IT4Innovations and use computer with fast processor for the transfer. Using Gigabit ethernet connection, up to 110MB/s may be expected. Fast cipher (aes128-ctr) should be used.

!!! Note "Note" If you experience degraded data transfer performance, consult your local network provider.

On linux or Mac, use scp or sftp client to transfer the data to Anselm:

local $ scp -i /path/to/id_rsa my-local-file username@anselm.it4i.cz:directory/file

local $ scp -i /path/to/id_rsa -r my-local-dir username@anselm.it4i.cz:directory

or

local $ sftp -o IdentityFile=/path/to/id_rsa username@anselm.it4i.cz

Very convenient way to transfer files in and out of the Anselm computer is via the fuse filesystem sshfs

local $ sshfs -o IdentityFile=/path/to/id_rsa username@anselm.it4i.cz:. mountpoint

Using sshfs, the users Anselm home directory will be mounted on your local computer, just like an external disk.

Learn more on ssh, scp and sshfs by reading the manpages

$ man ssh
$ man scp
$ man sshfs

On Windows, use WinSCP client to transfer the data. The win-sshfs client provides a way to mount the Anselm filesystems directly as an external disc.

More information about the shared file systems is available here.

Connection restrictions

Outgoing connections, from Anselm Cluster login nodes to the outside world, are restricted to following ports:

Port	Protocol
22	ssh
80	http
443	https
9418	git

!!! Note "Note" Please use ssh port forwarding and proxy servers to connect from Anselm to all other remote ports.

Outgoing connections, from Anselm Cluster compute nodes are restricted to the internal network. Direct connections form compute nodes to outside world are cut.

Port forwarding

Port forwarding from login nodes

!!! Note "Note" Port forwarding allows an application running on Anselm to connect to arbitrary remote host and port.

It works by tunneling the connection from Anselm back to users workstation and forwarding from the workstation to the remote host.

Pick some unused port on Anselm login node (for example 6000) and establish the port forwarding:

local $ ssh -R 6000:remote.host.com:1234 anselm.it4i.cz

In this example, we establish port forwarding between port 6000 on Anselm and port 1234 on the remote.host.com. By accessing localhost:6000 on Anselm, an application will see response of remote.host.com:1234. The traffic will run via users local workstation.

Port forwarding may be done using PuTTY as well. On the PuTTY Configuration screen, load your Anselm configuration first. Then go to Connection->SSH->Tunnels to set up the port forwarding. Click Remote radio button. Insert 6000 to Source port textbox. Insert remote.host.com:1234. Click Add button, then Open.

Port forwarding may be established directly to the remote host. However, this requires that user has ssh access to remote.host.com

$ ssh -L 6000:localhost:1234 remote.host.com

!!! note Port number 6000 is chosen as an example only. Pick any free port.

Port forwarding from compute nodes

Remote port forwarding from compute nodes allows applications running on the compute nodes to access hosts outside Anselm Cluster.

First, establish the remote port forwarding form the login node, as described above.

Second, invoke port forwarding from the compute node to the login node. Insert following line into your jobscript or interactive shell

$ ssh  -TN -f -L 6000:localhost:6000 login1

In this example, we assume that port forwarding from login1:6000 to remote.host.com:1234 has been established beforehand. By accessing localhost:6000, an application running on a compute node will see response of remote.host.com:1234

Using proxy servers

Port forwarding is static, each single port is mapped to a particular port on remote host. Connection to other remote host, requires new forward.

!!! Note "Note" Applications with inbuilt proxy support, experience unlimited access to remote hosts, via single proxy server.

To establish local proxy server on your workstation, install and run SOCKS proxy server software. On Linux, sshd demon provides the functionality. To establish SOCKS proxy server listening on port 1080 run:

local $ ssh -D 1080 localhost

On Windows, install and run the free, open source Sock Puppet server.

Once the proxy server is running, establish ssh port forwarding from Anselm to the proxy server, port 1080, exactly as described above.

local $ ssh -R 6000:localhost:1080 anselm.it4i.cz

Now, configure the applications proxy settings to localhost:6000. Use port forwarding to access the proxy server from compute nodes as well.

Graphical User Interface

• The X Window system is a principal way to get GUI access to the clusters.
• The Virtual Network Computing is a graphical desktop sharing system that uses the Remote Frame Buffer protocol to remotely control another computer.

VPN Access

• Access to IT4Innovations internal resources via VPN.