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ldconfig(8)

ldconfig(8) addresses two potential problems with shared libraries:

1. Speed: Shared libraries can reside in many different directories: it could take the dynamic linker a long time to search them.
   
   
2. Manually keeping sonames symlinks up to date is error-prone as new versions of libraries are installed, or old versions are removed.

ldconfig solves these problems by:

1. Creating a cache file:

   ldconfig searches for latest major library versions in:
   
   

   • all of the directories specified in /etc/ld.so.conf
   • /lib
   • /usr/lib

   
   and updates a cache file, /etc/ld.so.cache, to contain a list of the latest major library versions, and their locations.

   Cache file is used by dynamic linker at run-time when resolving library names.
   
   
2. Automating the creation of sonames:
   
   
   • ldconfig examines (the latest minor version of) each major version of each library to find the embedded soname, and
     
     
   • creates a relative symbolic link for this soname, in the same directory as the library.
     
     

In order to work properly, ldconfig relies on the use of the standard naming convention for shared libraries (i.e., libname.maj.min)

(C) 2006, Michael Kerrisk