Overview

Teaching: 15 min
Exercises: 30 min

Questions

• How do I access some CMS-specific software

Objectives

• Install the CVMFS on either your local machine or inside the Docker container

• Use CVMFS to access and run tools used to calculate the luminosity for specific run periods

At some point you may want to calculate the luminosity or study trigger effects for the data you are analyzing. CMS uses a tool called brilcalc but it is not included in the Docker image.

To get around this, we mount drives at CERN in the Docker container when you fire it up so that you can call this and perhaps other tools.

To learn more about brilcalc you can read the CERN Open Data Portal documentation. This lesson however is just to help you test that you can access this tool.

Installing CVMSFS

There are two ways to install CVMFS:

• Install CVMFS locally and then mount in the Docker container
• Install CMVFS directly in the Docker container

Installing CVMFS locally

From the CVMFS documentation

The CernVM-File System (CernVM-FS) provides a scalable, reliable and low- maintenance software distribution service. It was developed to assist High Energy Physics (HEP) collaborations to deploy software on the worldwide- distributed computing infrastructure used to run data processing applications. CernVM-FS is implemented as a POSIX read-only file system in user space (a FUSE module). Files and directories are hosted on standard web servers and mounted in the universal namespace /cvmfs.

In the following sections, we’ll direct you to the appropriate pages to download and install CVMFS locally. This should be done on your local machine and not in the container.

Let’s walk through these steps.

Get CVMFS

Follow the installation instructions to download the software for your particular OS.

Setup CVMFS

Next, you’ll want to set things up on your local machine. Follow these instructions carefully for your system.

One part of the setup which can be confusing is the content of the file /etc/cvmfs/default.local. The following lines should work, if they are the sole content of the file.

CVMFS_REPOSITORIES=cms.cern.ch,cms-opendata-conddb.cern.ch,cms-bril.cern.ch
CVMFS_HTTP_PROXY=DIRECT
CVMFS_CLIENT_PROFILE=single

Check the installation

Make sure you verify the installation. Check that link for the latest commands, but usually this involves running

sudo cvmfs_config setup

and then

cvmfs_config probe

or

sudo systemctl restart autofs

Possible issues

For some systems, you may run into some issues.

On WSL2 Ubuntu, after the installation, on each session, one has to run the following

sudo /usr/sbin/automount --pid-file /var/run/autofs.pid
cvmfs_config probe

You may even find that even during a session, you need to re-run

cvmfs_config probe

on your host machine, even on Linux or Mac.

Set up your Docker container

In the previous instructions on starting up your Docker container, we included the commands to start your container with CVMFS mounted.

... --volume "/cvmfs:/cvmfs:shared" ...

This makes sure the container can see this CVMFS file system.

If you ran all the correct commands in the previous exercise, you can now start the container by name

docker start -i myopendataproject

Or, if you wanted to start a brand new, fresh container with the CVMFS file system mounted, you can run

docker run -it --name mycvmfs --volume "/cvmfs:/cvmfs:shared" cmsopendata/cmssw_5_3_32 /bin/bash

If you want to simply build upon everything you have done already, your full Docker command would now look like

docker run -it --name myopendataproject --net=host --env="DISPLAY" --volume="$HOME/.Xauthority:/home/cmsusr/.Xauthority:rw" -v ${HOME}/cms_open_data_work:/home/cmsusr/cms_open_data_work:shared --volume "/cvmfs:/cvmfs:shared" cmsopendata/cmssw_5_3_32 /bin/bash

Install CVMFS directly in the Docker container

We’ll be following the offical CVMFS documentation here and here but with specific instructions for the CMSSW Docker image.

You’ll want to launch Docker with a new --privileged flag that will make it easier to install new packages. If we are using the full command from the previous module, it would now look like this

docker run --privileged -it --name myopendataproject --net=host --env="DISPLAY" --volume="$HOME/.Xauthority:/home/cmsusr/.Xauthority:rw" -v ${HOME}/cms_open_data_work:/home/cmsusr/cms_open_data_work:shared cmsopendata/cmssw_5_3_32 /bin/bash

The following command are all done in the Docker container.

Install the necessary packages using yum. This could take up to 30 minutes to install these packages.

At some point, the installation process will prompt you for your approval, Is this ok [y/N]:. You can enter y.

sudo yum install https://ecsft.cern.ch/dist/cvmfs/cvmfs-release/cvmfs-release-latest.noarch.rpm
sudo yum install -y cvmfs

Loaded plugins: changelog, kernel-module, ovl, protectbase, tsflags, versionlock
Setting up Install Process
cvmfs-release-latest.noarch.rpm                                                                                                          | 5.5 kB     00:00
Examining /var/tmp/yum-root-NokpI5/cvmfs-release-latest.noarch.rpm: cvmfs-release-2-6.noarch
Marking /var/tmp/yum-root-NokpI5/cvmfs-release-latest.noarch.rpm to be installed
EGI-trustanchors                                                                                                                         | 2.5 kB     00:00
EGI-trustanchors/primary_db                                                                                                              |  56 kB     00:00
.
<more output follows>
.

Next you’ll need to configure autofs, which handles mounting of filesystems.

sudo cvmfs_config setup

Edit the /etc/cvmfs/default.local file

sudo vi /etc/cvmfs/default.local

and add these lines:

CVMFS_REPOSITORIES=cms.cern.ch,cms-opendata-conddb.cern.ch,cms-bril.cern.ch
CVMFS_HTTP_PROXY=DIRECT
CVMFS_CLIENT_PROFILE=single

Restart autofs

sudo service autofs restart

Verify the file system

cvmfs_config probe

Heads-up!

You will need to repeat the last two commands every time you restart the container.

Test it out and run brilcalc

Once you are in the container and are in the CMSSW 5.3.32 environment, and have CVMFS working through either of the above methods, you can then run the following commands to set some local environment variables and then install brilcalc using the python pip command.

export PATH=$HOME/.local/bin:/cvmfs/cms-bril.cern.ch/brilconda/bin:$PATH

pip install --user brilws

Each time you login, you will have to re-run that export command, even if you have already installed brilws in the container.

If everything worked, you should be able to run brilcalc to check its version and to get the luminosity for a sample run.

Note that the first time you run the brilcalc commands, it can take up to 7 minutes to run!

brilcalc --version

brilcalc lumi -c web -r 160431

It should be noted that during the workshop, we will have an entire exercise dedicated to using this tool to calculate the luminosity for your datasets.

Key Points

• Installing CVMFS can make some parts of the analysis much easier

• Care must be given though to setting up your environment properly.