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RRZ
Regional Computing
Center (RRZ)

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Sharing files on Hummel-2

This page describes how to share files with members of the own working group.

On Hummel-2 the procedure for sharing files differs from the standard Linux procedure, where one would set read permission for the working group. (Never give write permissions to any other user, not even to members of your working group!)

How it works

The procedure on Hummel-2 is simpler (unless you changed the umask), because it suffices to move files to directories that are group-readable, for example:

$ mv $BEEGFS/group_data1 $BEEGFS_GROUPNAME
$ mv $USW/group_software1 $USW_GROUPNAME
$ mv $SSD/group_data2 $SSD_GROUPNAME

GROUPNAME must be typed all uppercase. Its spelling can be found in the output of the export command or via:

$ module display site/hummel2 | grep setenv

Of course files can also directly be created in $BEEGFS_GROUPNAME, $USW_GROUPNAME or $SSD_GROUPNAME.

  • Files in those directories are automatically group-readable (unless you changed the umask).
  • You must tell the other group members the names of your group directories. (The values of $BEEGFS_GROUPNAME and $USW_GROUPNAME can easily be guessed, the value of $SSD_GROUPNAME cannot.)
  • There is no $HOME_GROUPNAME.

Why it works

  • The primary Unix group has the same name as the username.
  • All personal directories ($HOME, $BEEGFS, $USW, $SSD) belong to the primary Unix group and are not readable by any other users.
  • There are group directories that are only accessible by the respective groups.
  • Below these are personal directories ($BEEGFS_GROUPNAME, $USW_GROUPNAME, $SSD_GROUPNAME).
  • The umask is set to 0022. In conjunction with directory ownerships and permissions set like specified above the behaviour described in How it works is achieved.