rivercottage said:
im quite new to macs....what exactly is repairing disk permitions?
Macs (OS X) run on Darwin which is really a unix OS.
Unix has a very comprehensive system of permissions based on owner, group and world users which can be assigned for any combination of reading/writing/executing and a few specials as well.
(as an example a file could be specified as rwx,r-x,r-- and be owned by user fred and belong to a group called athletes. These permissions will then mean that the owner can read, write and execute the file, anyone in group athletes can read and execute it and everyone else can only read it. A "super user" called root always has full access to every file and can change the ownership and group details of files and other users)
The "repair permissions" part of the disk utility Application simply runs through the specified filesystem and sanity checks the permissions it finds, if the permissions look wrong (i.e you have somehow made an executable type file unexecutable) it will attempt to correct them.
Note that it is not infallible but is always worth doing as a first attempt at fixing baffling problems.
Amen-Moses
