CernVM-FS Server Meta Information

The CernVM-FS server automatically maintains both global and repository-specific meta information as JSON data. Release manager machines keep a list of hosted Stratum0 and Stratum1 repositories and user-defined administrative meta information.

Furthermore each repository contains user-maintained signed meta-information that gets replicated to Stratum1 servers automatically.

Global Meta Information

This JSON data provides information about the CernVM-FS server itself. A list of all repositories (both Stratum0 and Stratum1) hosted at this specific server is automatically generated and can be accessed here:

http://<server base URL>/cvmfs/info/v1/repositories.json

Furthermore there might be user-defined information like the administrator’s name, contact information and an arbitrary user-defined JSON portion here:

http://<server base URL>/cvmfs/info/v1/meta.json

Using the cvmfs_server utility, an administrator can edit the user-defined portion of the data with a text editor (cf. $EDITOR)s:

cvmfs_server update-info

Note that the cvmfs_server package requires the jq utility, which validates CVMFS JSON data.

Below are examples of both the repository list and user-defined JSON files.

Repository Specific Meta Information

Each repository contains a JSON object with repository-specific meta data. The information is maintained by the repository’s owner on the Stratum0 release manager machine. It contains the maintainer’s contact information, a description of the repository’s content, the recommended Stratum 0 URL and a list of recommended Stratum 1 replica URLs. Furthermore it provides a custom JSON region for arbitrary information.

Note that this JSON file is stored inside CernVM-FS’s backend data structure and gets replicated to Stratum1 servers automatically.

Editing is done per repository using the cvmfs_server utility. As with the global meta information cvmfs_server uses jq to validate edited JSON information before storing it:

cvmfs_server update-repoinfo <repo name>

Besides the interactive editing (cf. $EDITOR) one can specify a file path that should be stored as the repository’s meta information:

cvmfs_server update-repoinfo -f <path to JSON file> <repo name>

An example of a repository-specific meta information file can be found in the section below.

Examples

/cvmfs/info/v1/meta.json

{
  "administrator" : "Your Name",
  "email"         : "you@organisation.org",
  "organisation"  : "Your Organisation",

  "custom" : {
    "_comment" : "Put arbitrary structured data here"
  }
}

/cvmfs/info/v1/repositories.json

{
  "schema"       : 1,
  "repositories" : [
    {
      "name"  : "atlas.cern.ch",
      "url"   : "/cvmfs/atlas.cern.ch"
    },
    {
      "name"  : "cms.cern.ch",
      "url"   : "/cvmfs/cms.cern.ch"
    }
  ],
  "replicas" : [
    {
      "name"  : "lhcb.cern.ch",
      "url"   : "/cvmfs/lhcb.cern.ch"
    }
  ]
}

Repository Specific Meta Information

{
  "administrator" : "Your Name",
  "email"         : "you@organisation.org",
  "organisation"  : "Your Organisation",
  "description"   : "Repository content",
  "url"           : "https://www.example.com/",
  "recommended-stratum0"  : "stratum 0 url",
  "recommended-stratum1s" : [ "stratum1 url", "stratum1 url" ],

  "custom" : {
    "_comment" : "Put arbitrary structured data here"
  }
}