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Install an OASIS Repository

OASIS (the OSG Application Software Installation Service) is an infrastructure, based on CVMFS, for distributing software throughout the OSG. Once software is installed into an OASIS repository, the goal is to make it available across about 90% of the OSG within an hour.

OASIS consists of keysigning infrastructure, a content distribution network (CDN), and a shared CVMFS repository that is hosted by the OSG. Many use cases will be covered by utilizing the shared repository; this document covers how to install, configure, and host your own CVMFS repository server. This server will distribute software via OASIS, but will be hosted and operated externally from the OSG project.

OASIS-based distribution and key signing is available to OSG VOs or repositories affiliated with an OSG VO. See the policy page for more information on what repositories OSG is willing to distribute.

Before Starting

The host OS must be:

  • RHEL8 or RHEL9 (or equivalent).

Additionally,

  • User IDs: If it does not exist already, the installation will create the cvmfs Linux user
  • Group IDs: If they do not exist already, the installation will create the Linux groups cvmfs and fuse
  • Network ports: This page will configure the repository to distribute using Apache HTTPD on port 8000. At the minimum, the repository needs in-bound access from the OASIS CDN.
  • Disk space: This host will need enough free disk space to host two copies of the software: one compressed and one uncompressed. /srv/cvmfs will hold all the published data (compressed and de-deuplicated). The /var/spool/cvmfs directory will contain all the data in all current transactions (uncompressed).
  • Root access will be needed to install. Installation of software into the repository itself will be done as an unprivileged user.
  • Yum will need to be configured to use the OSG repositories.

Installation

Installation is a straightforward install via yum:

root@host # yum install cvmfs-server osg-oasis

Apache and Repository Mounts

For all installs, we recommend mounting all the local repositories on startup:

root@host # echo "cvmfs_server mount -a" >>/etc/rc.local
root@host # chmod +x /etc/rc.local

The Apache HTTPD service should be configured to listen on port 8000, have the KeepAlive option enabled, and be started:

root@host # echo Listen 8000 >>/etc/httpd/conf.d/cvmfs.conf 
root@host # echo KeepAlive on >>/etc/httpd/conf.d/cvmfs.conf 
root@host # chkconfig httpd on 
root@host # service httpd start

Check Firewalls

Make sure that port 8000 is available to the Internet. Check the setting of the host- and site-level firewalls. The next steps will fail if the web server is not accessible.

Creating a Repository

Prior to creation, the repository administrator will need to make two decisions:

  • Select a repository name; typically, this is derived from the VO or project's name and ends in opensciencegrid.org. For example, the NoVA VO runs the repository nova.opensciencegrid.org. For this section, we will use <EXAMPLE.OPENSCIENCEGRID.ORG>.
  • Select a repository owner: Software publication will need to run by a non-root Unix user account; for this document, we will use <LIBRARIAN> as the account name of the repository owner.

The initial repository creation must be run as root:

root@host # echo -e "\*\\t\\t-\\tnofile\\t\\t16384" >>/etc/security/limits.conf
root@host # ulimit -n 16384
root@host # cvmfs_server mkfs -o <LIBRARIAN> <EXAMPLE.OPENSCIENCEGRID.ORG>
root@host # cat >/srv/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG>/.htaccess <<xEOFx
Order deny,allow
Deny from all
Allow from 127.0.0.1
Allow from ::1
Allow from 129.79.53.0/24 129.93.244.192/26 129.93.227.64/26
Allow from 2001:18e8:2:6::/56 2600:900:6::/48 
xEOFx

Here, we increase the number of open files allowed, create the repository using the mkfs command, and then limit the hosts that are allowed to access the repo to the OSG CDN.

Next, adjust the configuration in the repository as follows. 

root@host # cat >>/etc/cvmfs/repositories.d/<EXAMPLE.OPENSCIENCEGRID.ORG>/server.conf <<xEOFx
CVMFS_AUTO_TAG_TIMESPAN="2 weeks ago"
CVMFS_IGNORE_XDIR_HARDLINKS=true
CVMFS_GENERATE_LEGACY_BULK_CHUNKS=false
CVMFS_AUTOCATALOGS=true
CVMFS_ENFORCE_LIMITS=true
CVMFS_FORCE_REMOUNT_WARNING=false
xEOFx

Additionally, especially if files will be frequently deleted, enabling garbage collection is recommended in this way:

root@host # cat >>/etc/cvmfs/repositories.d/<EXAMPLE.OPENSCIENCEGRID.ORG>/server.conf <<xEOFx
CVMFS_GARBAGE_COLLECTION=true
CVMFS_AUTO_GC=false
xEOFx

The above assumes that you have your own mechanism to run cvmfs_server gc regularly (typically daily) at a time when it won't interfere with publications, since garbage collection and publication can't be done at the same time. CVMFS_AUTO_GC=true will automatically run garbage collection periodically after publications, but those times are not always convenient.

Also, check the cvmfs documentation for additional recommendations for special purpose repositories.

Now verify that the repository is readable over HTTP:

root@host # wget -qO- http://localhost:8000/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG>/.cvmfswhitelist | cat -v

That should print several lines including some gibberish at the end.

Hosting a Repository on OASIS

In order to host a repository on OASIS, perform the following steps:

  1. Verify your VO's registration is up-to-date. All repositories need to be associated with a VO; the VO needs to assign an OASIS manager in Topology who would be responsible for the contents of any of the VO's repositories and will be contacted in case of issues. To designate an OASIS manager, have the VO manager update the Topology registration.

  2. Send a message to OSG support using the following template:

    Please add a new CVMFS repository to OASIS for VO <VO NAME> using the URL
    http://<FQDN>:8000/cvmfs/<OASIS REPOSITORY>
The VO responsible manager will be <OASIS MANAGER>.

    Replace the <ANGLE BRACKET TEXT> items with the appropriate values.

  3. If the repository name matches *.opensciencegrid.org or *.osgstorage.org, wait for the go-ahead from the OSG representative before continuing with the remaining instructions; for all other repositories (such as *.egi.eu), you are done.

  4. When you are told in the ticket to proceed to the next step, first if the repository might be in a transaction abort it:

    root@host # su <LIBRARIAN> -c "cvmfs_server abort <EXAMPLE.OPENSCIENCEGRID.ORG>"

    Then execute the following commands:

    root@host # wget -O /srv/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG>/.cvmfswhitelist \
            http://oasis.opensciencegrid.org/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG>/.cvmfswhitelist
root@host # cp /etc/cvmfs/keys/opensciencegrid.org/opensciencegrid.org.pub \
            /etc/cvmfs/keys/<EXAMPLE.OPENSCIENCEGRID.ORG>.pub

    Replace <EXAMPLE.OPENSCIENCEGRID.ORG> as appropriate. If the cp command prompts about overwriting an existing file, type 'y'.

  5. Verify that publishing operation succeeds:

    root@host # su <LIBRARIAN> -c "cvmfs_server transaction <EXAMPLE.OPENSCIENCEGRID.ORG>"
root@host # su <LIBRARIAN> -c "cvmfs_server publish <EXAMPLE.OPENSCIENCEGRID.ORG>"

    Within an hour, the repository updates should appear at the OSG Operations and FNAL Stratum-1 servers.

    On success, make sure the whitelist update happens daily by creating /etc/cron.d/fetch-cvmfs-whitelist with the following contents:

    5 4 * * * <LIBRARIAN> cd /srv/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG> && wget -qO .cvmfswhitelist.new http://oasis.opensciencegrid.org/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG>/.cvmfswhitelist && mv .cvmfswhitelist.new .cvmfswhitelist

    Note

    This cronjob eliminates the need for the repository service administrator to periodically use cvmfs_server resign to update .cvmfswhitelist as described in the upstream CVMFS documentation.

  6. Update the open support ticket to indicate that the previous steps have been completed

Once the repository is fully replicated on the OSG, the VO may proceed in publishing into CVMFS using the <LIBRARIAN> account on the repository server.

Tip

We strongly recommend the repository maintainer read through the upstream documentation on maintaining repositories and content limitations.

Finally, if the new repository will be used outside of the U.S., the VO should open a GGUS ticket following EGI's PROC20 to get the repository replicated onto worldwide Stratum 1s.

Replacing an Existing OASIS Repository Server

If a need arises to replace a server for an existing *.opensciencegrid.org or *.osgstorage.org repository, there are two ways to do it: one without changing the DNS name and one with changing it. The latter can take longer because it requires OSG Operations intervention.

Revision numbers must increase

CVMFS does not allow repository revision numbers to decrease, so the instructions below make sure the revision numbers only go up.

Without changing the server DNS name

If you are recreating the repository on the same machine, use the following command to remove the repository configuration while preserving the data and keys:

root@host # cvmfs_server rmfs -p <EXAMPLE.OPENSCIENCEGRID.ORG>

Otherwise if it is a new machine, copy the keys from /etc/cvmfs/keys/<EXAMPLE.OPENSCIENCEGRID.ORG>.* and the data from /srv/cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG> from the old server to the new, making sure that no publish operations happen on the old server while you copy the data.

Then in either case use cvmfs_server import instead of cvmfs_server mkfs in the above instructions for Creating the Repository, in order to reuse old data and keys. Note that you wil need to reapply any custom configuration changes under /etc/cvmfs/repositories.d/` that was on the old server.

If you run an old and a new machine in parallel for a while, make sure that when you put the new machine into production (by moving the DNS name) that the new machine has had at least as many publishes as the old machine, so the revision number does not decrease.

With changing the server DNS name

Note

If you create a repository from scratch, as opposed to copying the data and keys from an old server, it is in fact better to change the DNS name of the server because that causes the OSG Operations server to reinitialize the .cvmfswhitelist.

If you create a replacement repository on a new machine from scratch, follow the normal instructions on this page above, but with the following differences in the Hosting a Repository on OASIS section:

  • In step 2, instead of asking in the support ticket to create a new repository, give the new URL and ask them to change the repository registration to that URL.

  • When you do the publish in step 5, add a -n NNNN option where NNNN is a revision number greater than the number on the existing repository. That number can be found by this command on a client machine:

    user@host $ attr -qg revision /cvmfs/<EXAMPLE.OPENSCIENCEGRID.ORG>

  • Skip step 6; there is no need to tell OSG Operations when you are finished.

  • After enough time has elapsed for the publish to propagate to clients, typically around 15 minutes, verify that the new chosen revision has reached a client.

Removing a Repository from OASIS

In order to remove a repository that is being hosted on OASIS, perform the following steps:

  1. If the repository has been replicated outside of the U.S., open a GGUS ticket assigned to support unit "Software and Data Distribution (CVMFS)" asking that the replication be removed from EGI Stratum-1s. Remind them in the ticket that there are worldwide Stratum-1s that automatically replicate all OSG repositories that RAL replicates, so those Stratum-1s cannot remove their replicas before RAL does but their administrators will need to be notified to remove their replicas within 8 hours after RAL does to avoid alarms. Wait until this ticket is resolved before proceeding.
  2. Open a support ticket asking to shut down the repository, giving the repository name (e.g., <EXAMPLE.OPENSCIENCEGRID.ORG>), and the corresponding VO.
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