> Actually it meant the "text" segment (code and constant data) was > write-protected during execution, and hence could be shared between > multiple processes executing the same program. In fact that's why it was > called the "sticky" bit -- the text segment could stick in RAM even if > the process was swapped out, and in fact never needed to be swapped out > because it could always be reloaded from the executable file. This is > now assumed in the case of modern paging systems, but in the old PDP-11 > it wasn't available on all models and could in some corner cases reduce > the total amount of virtual memory available to the process (you only > had a total of 8 physical segments of up to 32Kb each, and the stack > took up at least 1; later models allowed 16 segments total but 8 could > only be text and 8 could only be data or stack). Hence it had to be > user-modifiable. [although you needed a later 2.x BSD to utilise anything beyond 64K code 64K data. 2BSD could do segment handling stuff [think DOS EMS and try not to get flashbacks from the horror] > Now I'm showing my age :-) The V7 manual doesn't quite agree with you. The sticky bit simply indicates that the code segment for the binary should be kept around in memory/swap (fast storage) not discarded. It might get set on a tiny number of root apps to tune performance. Anyone who remembers "resident" on the Amiga has the right idea. It did require on the 11 that the program was split I/D so there was an unmodifiable code segment but that's an implementation detail for that architecture. Some Unixen today still honour the sticky bit for executables - but not many. As it was only relevant for executables it also got borrowed for other bits. For directories it indicates that only the file owner can unlink(remove) files - mostly to fix /tmp. A couple of systems use it for other 'magic' on non-executable files. Alan -- users mailing list users@xxxxxxxxxxxxxxxxxxxxxxx To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines
