Wednesday, 6 July 2011

cvmfs installation

Last week after few months delay I finally installed cvmfs. It's since 2002-2003 that I advocate the use of a shared file system for the input sandbox with locally cached data. AFS was successfully used in grid and non grid environment by BaBar users and is still used by local non-LHC users in Manchester for small work. So I'm pretty happy that a light weight caching file system is now available for more robust traffic. This is a really good moment to install cvmfs for two reasons:

1) Lhcb asked for it too.
2) Atlas has moved its condb files from the HOTDISK space token to cvmfs.

And it should reduce drastically errors for both NFS and SE load.

These are my installation notes:

* Install cernvm.repo: you can find it here or you can copy the rpms in your local and install from there. I distribute the file with cfengine but otherwise

cd /etc/yum.repos.d/

* Install the gpg key: yum didn't like the key and was giving errors. I don't know if the problem is only mine (possible) I anyway told the developers and in the meantime I had to remove the key check from the repo file and trust the rpms. But if you want to try it, it might work for you:

cd /etc/pki/rpm-gpg/

* Install the rpms. In the documents there is an additional rpm cvmfs-auto-setup which is not really necessary and was also causing problems due to some migration lines devised for upgrades. Other than that it runs a setup and a restart command that can be run by your configuration tool of choice. S. Traylen also suggested to install SL_no_colorls to avoid ls /cvmfs mounting all the file systems that's why it's in the list.

yum install -y fuse cvmfs−keys cvmfs cvmfs−init−scripts SL_no_colorls

* Install configuration files. Below is what I added. For atlas there is in the docs a nightlies repository but that's not ready yet and isn't going to work. The default QUOTA_LIMIT set in default.local can be overridden in the experiment configuration. For each of this files there is a .conf file and a .local you should edit only .local. If they are not there just create them.
You need to override the CVMFS_SERVER_URL for atlas otherwise you don't get the new setup. While in I simply inverted the order of the server to get RAL first and then the other two if RAL fails. I also removed CERNVM_SERVER_URL which appears in otherwise it goes to CERN first even though it's not apparently defined anywhere.





* Create the cache space. By default it's in /var/cache. However I moved it to the /scratch partition which is bigger.

mkdir -p /scratch/var/cache/cvmfs2
chown cvmfs:cvmfs /scratch/var/cache/cvmfs2
chmod 2755 /scratch/var/cache/cvmfs2

* Run the setup. These are the commands the cvmfs-auto-setup would run at installation time. They also configure fuse although that's only one line added to fuse.conf.

/usr/bin/cvmfs_config setup
service cvmfs restartautofs

chkconfig cvmfs on
service cvmfs restart

* Some parameters need to change for squid. Below is what the documentation suggests. I tuned it to the size of my machine. For example the maximum_object_size and cache_mem were too big and I checked which other parameters were already set to evaluate if it was the case to change them.

collapsed_forwarding on
max_filedesc 8192
maximum_object_size 4096 MB
cache_mem 4096 MB
maximum_object_size_in_memory 32 KB
cache_dir ufs /var/spool/squid 50000 16 256

* Apply changes for Lhcb the VO_LHCB_SW_DIR needs to point to cvmfs. You can change it in YAIM and rerun it or you can do as I've done (still making sure to change YAIM so that freshly installed nodes don't need this hack). Lhcb with this change is good to go.

sed -i.sed.bak 's%/nfs/lhcb%/cvmfs/' /etc/profile.d/
mv /etc/profile.d/ /root

* Apply changes for Atlas. A similar change to VO_ATLAS_SW_DIR is required and you need to set an additional variable that is not handled by YAIM. For now I added it to but it be better placed in another file not touched by YAIM or a snippet should be added to YAIM to handle the variable. This is enough for the jobs to start using the software area. However you still have to contact the atlas sw team to do their validation tests and enable the condb use. They'll propose a long way and a short way. I took the short because I didn't want to go in downtime and jobs were already running using the new setup.

sed -i.sed.2 's%"/nfs/atlas"%"/cvmfs/"\ngridenv_set "ATLAS_LOCAL_AREA" "/nfs/atlas/local"%' /etc/profile.d/
mv /etc/profile.d/ /root

* Always for Atlas remove some installed .conf files which install a link in /opt which is not necessary anymore. Second file might not exist, but there is an This will surely change in future cvmfs releases.

service cvmfs stop
rm /etc/cvmfs/config.d/
rm /etc/cvmfs/config.d/
service cvmfs start

Update 12/7/2011: Using YAIM

cfengine only installs the rpms and the configuration files (*.local). All the rest is now carried out by a YAIM function I created (config_cvmfs). I put a tar file here.To make it work I also added a node description in node-info.d/cvmfs (also in the tar file) that contains it. In this way I don't have to touch any already existing YAIM files and I can just add -n CVMFS to the YAIM command line we use to configure the WNs. It requires ATLAS_LOCAL_AREA and CVMFS_CACHE_DIR variables to be set in your site-info.def.

CVMFS docs are here

Release Notes
Init Scripts Overview
Technical Report
Atlas T2/T3 setup
Atlas latest changes

1 comment:

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