Slide 1 Structured Naming

Slide 2 Given Credit Where It Is Due The following slides are borrowed from Dr. Katerina Goseva-Popstojanova at West Virginia University

Slide 3 Name Spaces Absolute path name: the first node in the path name is the root of the naming graph. Example: n o Otherwise relative path name

Slide 4 Name Spaces Global name – denotes the same entry, no matter where that name is used in a system Local name – interpretation depends on where the name is being used (e.g., environmental variable such as HOME in UNIX) There are many different ways to organize a name space –Tree (strictly hierarchical) –Directed acyclic graph as in the previous slide

Slide 5 Name Spaces The general organization of the UNIX file system implementation on a logical disk of contiguous disk blocks

Slide 6 Name resolution Name resolution - the process of looking up a name Closure mechanism – deals with selecting the initial node in a name space from which to start the name resolution –In UNIX file system, the inode of the root directory is the first inode in the logical disk representing the file system Resolving a name requires that some mechanism has already been implemented by which the resolution process can start –Example:

Slide 7 Linking and Mounting Alias – another name for the same entry –Example: environmental variable such as HOME Two different ways to implement an alias: –Hard links – allow multiple absolute path names to refer to the same node (e.g., /keys and /home/steen/keys ) –Symbolic links – represent an entry by a leaf node that stores an absolute path name

Slide 8 Linking and Mounting The concept of a symbolic link explained in a naming graph

Slide 9 Linking and Mounting Name resolution can be used to merge different name spaces in a transient way Mounted file system corresponds to letting a directory node store the identifier of a directory node from different (foreign) name space –Mount point – directory node storing the node identifier –Mounting point – directory node in the foreign name space

Slide 10 Linking and Mounting To mount a foreign name space in a distributed system requires at least –Name of an access protocol –Name of the server –Name of the mounting point in the foreign name space Each of this needs to be resolved None of these may be needed in non-distributed systems (e.g., UNIX)

Slide 11 Linking and Mounting Mounting remote name spaces using Sun’s Network File System (NFS)