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Kilian Holzapfel edited this page Jun 28, 2022 · 10 revisions

LRZ Documentation

This project uses 2 different LRZ tools. The DSS is the storage backend and the Compute Cloud hosts VMs. (Maybe also the Linux Cluster in the future.)

Overview

For STRAW and STRAWb, the STRAW-LRZ-VM runs 24/7, has 1 CPU with 4.5 GB RAM and therefore takes care of synchronising the module data from the ONC DB and monitoring both detectors. But it can also do some simple calculations. For more power, another VM has to be set up. On the VM the DSS-Storage is mounted to /dss.

DSS

The digital scientific storage (DSS) is s service provided by the LRZ (Munich). Here are the official docs for more information. You can access the DSS in two different ways.

  1. Mount the DSS container, e.g., on a VM hosted by the Compute Cloud. Important only a device with a mwn IP can mount the container. The section Mounting the DSS at a VM describes the required steps.
  2. Access the DSS via Globus which is a web-application similar to any cloud storage. The section Globus describes the required steps.

Management platform

At the DSS management webpage https://dssweb.dss.lrz.de (only accessible within the TUM network, in case use a VPN connection), persons with management permission see the DSS Containers. There you can manage the members, add NFS exports and more.

Globus

A platform to share data like a OwnCloud, NextCloud, DropBox, GoogleDrive, or similar which is linked to the DSS. At the Globus webpage you can log in with your LRZ credentials. By default, your account isn't granted access to the DSS. To do so, follow the registration section.

When your registration was successfully, you can select in the File Manager-tab (default after you log in at Globus):

Collection Leibniz Supercomputing Centre's DSS - CILogon
Path /dss/dsstumfs02/pn69gu/pn69gu-dss-0004/

and set a bookmark for a faster access the next time.

Registration

Before you can use Globus the first time, you have to do register that your LRZ credential gets the privileges for Globus.

The registration can take a while until it's transferred to the Globus server. Afterwards, you can log in with your LRZ credentials and access the DSS at https://app.globus.org/

Compute Cloud - VM hosting

The Compute Cloud is a VM hosting service of the LRZ. Here are the official docs. By default, a project has 10 CPU cores with 4.5 GB RAM per Core. The RAM ratio is fixed, but the total number of CPU cores can be higher. Therefore, contact the LRZ service desk.

The VMs among projects share the same hardware. Once a VM is active, it blocks the resource. Therefore, it is important to only activate (un-shelf) the VMs if needed and deactivate (shelf) them afterwards. However, VMs with one Core per project can run constantly. Those VMs can do regular jobs which do not require much computation power and can be an entry point to (un-)shelf other VMs which do more intense jobs. (How this works in an automated manner has to be figured out.)

This chapter contains the following sections:

Hosted VMs - Parameters and shh_config entries

The list of actual hosted VMs.

VM Name resources <user_name> <ip_address>
STRAW-LRZ-VM Active 24/7, 1 CPU, 4.5GB di46lez 138.246.233.224
Computing can be shelved if not needed, 4 CPU, 18GB di46lez 138.246.236.150

SSH config entries

SSH config entries to add to ~/.ssh/config:

Host straw-lrz-vm
    User            di46lez
    HostName        138.246.233.224
    IdentityFile    ~/.ssh/cloud.key
  
Host strawbcomputing
    User            di46lez
    HostName        138.246.236.150
    IdentityFile    ~/.ssh/cloud.key

VM management-portal

The VM management-portal is https://cc.lrz.de. To login there, you need a special LRZ-ID similar to your normal LRZ-ID but different. For the moment this is: di46lez (password is posted in Slack, search for the ID).

IPs

You can assign a floating IP to a VM. This IP will never change unless you disassociate (unlink) it from the VM.

You can manage the floating IPs at the management-portal-> Project -> Network -> Floting IPs. To add a new IP, click Allocate IP To Project. The mwn_pool is not exposed and therefore not accessible from the internet, which is a major security issue. In contrast, the internt_pool is accessible and exposed to the internet.

Key Pairs

You can add key pairs with management-portal-> Project -> Compute -> Key Pairs. All key pairs are added to new created VMs only. For existing VMs you have to add the keys manually to each machine. For more instructions about the ssh key see the dedicated section.

Access a VM via SSH

The access to a VM is restricted to ssh with key pair only. First create a new key pair. If you don't know how, search the internet for it. In the following the key To add a key, someone with access to the VM has to add your public part (.pub) of the ssh key to the file ~/.ssh/authorized_keys on the VM. Afterwards you can log in with

ssh -i <your_key.key> <user_name>@<ip-address>

Replace <your_key.key> with the path to your .key file (not the .pub). The <user_name> and <ip-address> are in the table of hosted VMs.

SSH config

To make the ssh command easier, you can set parameter pairs in the ssh-config file. The file is located on your computer at ~/.ssh/config and add the following lines:

Host <name_of_the_vm>
    User            <user_name>
    HostName        <ip-address>
    IdentityFile    <your_key.key>

Replace <name_of_the_vm> with any name you want. Save the file. Now the ssh command reduce to:

ssh <name_of_the_vm>

In addition, the <name_of_the_vm> works with rsync, and scp.

Some examples to use a VM

Copy files from/to the VM with rsync or scp

To sync files between different machines (but also on the same machine) you can use scp or rsync. The usage, especially with a ssh-config is straight forward, e.g., to download/upload files from/to the VM:

rsync <name_of_the_vm>:"/path/to/files/*.txt" target/dir  # downloads files all txt-files from /path/to/files/
rsync target/dir/*.txt <name_of_the_vm>:"/path/to/files"  # upload files all txt-files from target/dir/
rsync <name_of_the_vm>:"/path/to/files" target/dir/files  # download the whole directory
rsync <name_of_the_vm>:"/path/to/files/" target/dir  # equals the line above

For directories, you have to take care to set the source string in the right syntax. Without or with a tailing / makes the different. Compare the last two lines of the example. Furthermore, there are many documentations - like - explaining the difference and the various options.

Jupyter Notebook

A jupyter notebook server is running on the STRAW-LRZ-VM at port 8080. To use it, on your computer:

  1. open a tunnel from your computer: ssh -L 8080:localhost:8080 <name_of_the_vm> and leave the terminal open incl. the ssh connection.
  2. open http://localhost:8080 in the browser, PW: strawb

(Re-)start the server, on the VM

Log in to the VM via ssh -L 8080:localhost:8080 straw-lrz-vm or ssh straw-lrz-vm , does not matter. For the restart, make sure that the old process isn’t running at the target port. For this, get the PID with e.g., ps -ef | grep jupyter-notebook or htop or similar. In case, kill it with kill <PID>.

jupyter notebook --no-browser --port=8080&; disown

From &; disown; & will put the task in background and disown unlinks it from the user, as closing the ssh connection will stop all linked processes.

Ports

You can also use any other port on your end or the vm, e.g., if you connect to different machines at once. On the VM start the server with an updated --port=<VM_PORT> ; <VM_PORT> can be any unused port The tunnel:

ssh -L <LOCAL_PORT>:localhost:<VM_PORT> <name_of_the_vm>

has to match the <VM_PORT> and <LOCAL_PORT> can be any unused port + http://localhost:LOCAL_PORT

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