Using XtreemOS

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Contents

Getting familiar with XtreemOS

If you are new to XtreemOS, you might want to take a look at the user guide. The latest version is here: XOS_UserGuide_20091014.pdf

Even if you are familiar with XtreemOS, it is recommended to look at the user guide, as it describes recent XtreemOS 2.0 features. What you should read from the guide:

  • Chapter 2 (Overview)
  • Section 4.3 (Application Execution Management)
  • Section 4.5 (XOSAGA)

Unfortunately this is a draft version of the user guide and some sections are still missing.

The VU Testbed

Currently the testbed consists of 3 machines:

  • core.xtreemos.cs.vu.nl (core node + resource)
  • node01.xtreemos.cs.vu.nl (resource + client node)
  • node02.xtreemos.cs.vu.nl (resource + client node)

Note: These machine names are aliases for the following names (in order): node004.das2.cs.vu.nl, node006.das2.cs.vu.nl, node007.das2.cs.vu.nl.

Creating a user account

In order to use XtreemOS you have to be registered in a virtual organization (VO). There is a web interface through which you can request to be included in a VO – here are the steps to do this:

1. Go to the VOLifeCycle portal and make yourself a new account: http://core.xtreemos.cs.vu.nl:8080/volifecycle
Write an e-mail to cstratan at cs.vu.nl to approve the account.

2. Log in using this account and go to Generate new keypair. Press the Generate button and then press the Download button - this way you will get a private key (a user.key file).

3. Go to Join a VO and choose to join VU_XOS20_new (this is the virtual organization that we are currently using for tests). Write another e-mail to cstratan at cs.vu.nl and I will add you to the VO and make accounts for you on the machines. (I know, it's annoying that you need to contact the admin 2 times just to get an account on VOLife)

4. After you were added to the VO, log in again to the portal and go to Get an XOS-Cert. Download the new certificate and you will have a user.crt file. With this certificate you can prove that you are in the VU-XOS20_new virtual organization.

Setting up the certificates

In order to execute jobs in XtreemOS, you have to log into one of the client machines (node01, node02). You will need to put your key and your certificate on that machine, in the $HOME/.xos/truststore/private and $HOME/.xos/truststore/certs directories (you have to create these directories first). There are more details about certificates in Section 4.1 from the user guide (but the section about VOLife is not complete).

Setting up XtreemFS automount

When you submit a job, you need to set up XtreemFS in order to be able to get the output files that the job generates; XtreemOS does not do any file stage-out and the output files will just remain on the machine where the job was executed if XtreemFS is not set up (and you probably will not be able to access them). XtreemOS can mount a home volume for you (almost) automatically; then you can make your jobs write the output files in that home volume. In order to enable the auto-mounting, you have to write another e-mail to cstratan at cs.vu.nl, AFTER you have put your certificate in $HOME/.xos/truststore/certs. I will create your home volume and after that it can be mounted automatically.

Using ssh-xos

After XtreemFS automount was enabled for you, you will be able to access your home volume by using ssh-xos. Your home volume will be automatically mounted when you log in with ssh-xos, in the /home/<GUID> directory, where GUID is your global user ID. You can see your global user ID by looking at your user certificate, with the following command:

view-xos-cert $HOME/.xos/truststore/certs/user.crt

(search for “GlobalUserID:”; or search for “Subject:” and remove the “CN=” prefix). For example, for the user xosuser, this ID is: 18f71ca3-fda7-497d-9a97-e14dbad5ad90. After logging in with ssh-xos, you can see a directory with this name in /home/.

You will be able to ssh-xos to all the nodes (core, node01, node02) with a command like this:

ssh-xos node01

You can connect to any node, including the one on which you are already logged in. You will be asked for the passphrase of your private key (note: if you are asked for the account password instead of the passphrase, something is going wrong. Make sure that your key and certificate files are in the right places; if it still doesn't work, e-mail the VO admin :-) ). When you connect, the XtreemFS volume will be automatically mounted and you will be able to read/write files from it. When you disconnect (Ctrl-D), the volume will be unmounted.

Submitting jobs

For details about how to submit jobs, see section 4.3 from the user guide.

In order to be able to retrieve the output of the jobs, you need to set the output files to be in your XtreemFS home volume. For example, a JSDL file of the user xosuser should contain:

<Output>/home/18f71ca3-fda7-497d-9a97-e14dbad5ad90/out_file.txt</Output>
<Error>/home/18f71ca3-fda7-497d-9a97-e14dbad5ad90/err_file.txt</Error>

This also applies to the input files, in case your job has input files. You don't need to be logged in with ssh-xos when submitting jobs, but you have to log in at least afterwards, so that you can access the output files (or before, if you have input files and need to put them in the home volume).

For more information

If you have questions, you can also ask on the XtreemOS users mailing list: http://lists.gforge.inria.fr/cgi-bin/mailman/listinfo/xtreemos-users

or on the XtreemOS IRC channel: irc.freenode.net#xtreemos-dev


Old version of the user guide

Here the user guide for the old VU testbed (the one with XtreemOS 1.0): Xtreemos user howto VU.pdf

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