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Structured Naming

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Example: no home, steen, mbox Otherwise relative path name. Slide 4. Name Spaces ... absolute path names to refer to the same node (e.g., /keys and /home/steen/keys) ... – PowerPoint PPT presentation

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Title: Structured Naming


1
Structured Naming
2
Given Credit Where It Is Due
  • The following slides are borrowed from Dr.
    Katerina Goseva-Popstojanova at West Virginia
    University

3
Name Spaces
  • Absolute path name the first node in the path
    name is the root of the naming graph. Example
    nolthome, steen, mboxgt
  • Otherwise relative path name

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

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

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 130429304052523

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

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

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 (normally the root of a name space)

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)

11
Linking and Mounting
  • Mounting remote name spaces using Suns Network
    File System (NFS)

12
Example
  • Domain Name System
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