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Share data without data duplication using nfs4_acls and hard links

Project description



Using PyPi:

pip install nfs4_share

Or install from source:

  1. clone the repository

  2. cd into the repository directory

  3. Install using:

         pip install .


Run nfs4_share --help for arguments. A more detailed description can be found below


Typically Within the high-performance clusters a bulkstorage is exposed as a mount with type Network Filestorage System version 4 (NFSv4). To protect the data only limited read access is granted and to an even lesser degree write access is granted. Playing safe can become a problem when the need arises to share the results with other researchers members. Manually providing and revoking access on an NFSv4 is possible but cumbersome and error prone. Simply copying the data to a shared location is dangerous and very quickly increases usage of expensive storage. This can be very expensive.

The NFSv4-SHARE program is build to solve this problem. It uses properties of the NFSv4 mount to prevent data duplication and makes keeping track of permissions relatively easy. Data duplication is prevented by only creating hard-links to files. Keeping track of permissions is done by wrapping the hard-linked files in a directory that all share the same permissions.

Access to the data and shares itself is controlled by NFSv4 access-control lists (ACLists). These ACLists consist of entries (ACEntries) which determine what permissions a calling user has. The main differences between ACLists and the standard POSIX permissions (i.e. rwxrwxrwx) are as follows:

  • multiple users and groups can be defined
  • more fine-grained permissions can be controlled (13 for files, 14 for directories).

A small addition has been made to also control the .htaccess file of a share to allow data sharing via an apache server.

Practical Example

Take some imaginary source data that is structured as follows:


If you want to do the following:

  • create a share for project foobar under /shares
  • share the file QC.txt from directory /data/results
  • share the subdirectory sample1/ from directory /raw_data
  • provide access to user bob and alice
  • manage the share with group pmc_omics

You run the following command:

	nfs4_share create /shares/foobar \
	--users bob alice \
	--managing_groups pmc_omics \
	--items /data/results/QC.txt /raw_data/sample1

You then end up with a share and source data that is structured as follows:


Users bob and alice could then navigate to the share at /shares/foobar to access the shared data.

When they finish or you need to recreate the share, use NFSv4-SHARE to delete the share:

	nfs4_share delete /shares/foobar

Implementation Details

The ACLists on the share directory (i.e. /shares/foobar) are the de facto share permissions.

Shared Files

Within the example above, all the files have the original ACEntries. These NEED to include reading permissions.

Shared Directories

Any subdirectories from the source that end up in foobar are different subdirectories(!). The directories from the specified source items have their tree freshly rebuild within the share. For instance, the directory /shares/foobar/sample1 is not a hard-link to /raw_data/sample1, but a remake. The directories share the name sample1 but have a different inode number and associated ACList. Within the foobar share, the ACList of directory sample1 only has the ACEntries required to have bob and alice read and index files.

Unit tests

If the source code is located on an NFSv4 mount with ACLs enabled you can run unit tests as follows:

pip install .[test]
pytest --basetemp=<NFS4_MOUNT>

If the source code is not stored on an NFSv4 mount, you should first move it to an NFSv4 mount before unit testing.

Luckily, this is already automated in the following script. It will push the source code to the remote server and have the unittest runs there locally.

bash tests/ <ssh_remote_host> <remote_working_directory> <remote_nfs4_mount_for_creating_shares> <test_variables.json>

example: bash tests/ gwhorus test_shares_exc /data/isi/p/pmc_research/omics/development/shares tests/variables_UMC.json

In case you are working on a cripled OS lacking the "realpath" function then use

Python Module Interface

If you want to programmatically call this program within python you can use something as follows:

from nfs4_share.manage import create, delete

                items=["file1.txt", "file2.txt"])

Upload new version to PyPi

This requires an account at with access to the project.

  1. Change the version number in ./

  2. Tag a new version

     git tag v0.1.0
  3. Install required packages for uploading

     pip install --upgrade setuptools wheel twine
  4. Build dist

     python sdist bdist_wheel
  5. Upload using twine

     twine upload dist/*

Project details

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