To execute an HSI command involving local or HPSS files successfully, the user must have access privileges to all nodes of the path as follows:

• execute access to search all directories up to the directory containing the file or directory node affected by the request
• read access to LIST directories or GET file nodes
• write access to the parent directory to MKDIR (new directory) or SAVE new file nodes
• write access to the file node if it is being overwritten

If you expect to share files with other users, you will need to understand access rights. All files are protected against the access of an unauthorized user, unless this protection is changed explicitly by using the CHMOD or CHOWN commands.

When your HPSS account is established, you are established as a member of one or more groups.

The list of groups to which you belong is referred to as your group vector. When HPSS checks group access permissions, it uses the group vector to determine whether you are a member of the owning group for the node.

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The HPSS system administrator can create Group Directories (public directories with group access rights set up to allow only members of a certain group to work with files and subdirectories within that directory). This is the recommended method for sharing files with several persons who are all working on a related project. Contact the HPSS administrator for help in setting up such a public directory.

You can also permit other members of your group to access your home directory by appropriately setting access permissions with the CHMOD command.

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Each NERSC User is assigned to a "Group" within HPSS that is associated with the user's "repository"; this is an accounting entity in which CPU time and storage allocations are maintained. However, special HPSS "Project Groups" are also available for the express purpose of expediting files sharing among specific groups of users, even if they belong to different repositories. A Project Group provides a separate "home" directory, independent from those of the member individuals. Storage usage charges incurred by a Project Group are levied against a specified repository, usually that of the individual who requested its creation. Project Groups require special setup, which is done only on request. To inquire about this, send email to consult@nersc.gov.

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HPSS supports ACLs for multilevel security. However, ACL support is not included in HSI at this time.

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