more sticky explanations.

share/man/man7/sticky.7

@@ -1,4 +1,4 @@
-.\"	$NetBSD: sticky.7,v 1.2 2004/01/30 15:38:18 wiz Exp $
+.\"	$NetBSD: sticky.7,v 1.3 2004/01/30 16:06:20 christos Exp $
 .\"
 .\" Copyright (c) 1980, 1991, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -29,7 +29,7 @@
 .\"
 .\"     @(#)sticky.8	8.1 (Berkeley) 6/5/93
 .\"
-.Dd May 25, 1998
+.Dd January 30, 2004
 .Dt STICKY 7
 .Os
 .Sh NAME
@@ -49,6 +49,9 @@ or the file
 The use of mode
 .Dv S_ISVTX
 is reserved and can be set only by the super-user.
+.Nx
+does not currently treat plain files that have the sticky bit set specially,
+but this behavior might change in the future.
 .Sh STICKY DIRECTORIES
 A directory whose
 .Dq sticky bit
@@ -68,20 +71,28 @@ See
 .Xr chmod 1
 for details about modifying file modes.
 .Sh HISTORY
-The sticky bit first appeared in
-.Bx 4.1 .
-Its initial use was to mark executables that were frequently used
-so that their text would stay in virtual memory after the process
-exited.
+The sticky bit first appeared in V7, and this manual page appeared
+in section 8.  It's initial use was to mark sharable executables
+that were frequently used so that they would stay in swap after
+the process exited.  Sharable executables were compiled in a special
+way so their text and read-only data could be shared amongst
+processes.
+.Xr vi 1
+and
+.Xr sh 1
+were such executables.
 This is where the term
 .Dq sticky
-comes from - the text of the program would stick around in virtual
-memory.
-Such executables were compiled in a way that they would have their
-read-only data loaded in the text segment to minimize the amount of
-work needed to load the executable.
-.Xr vi 1
-was one such executable.
+comes from - the program would stick around stick around in swap,
+and it would not have to be fetched again from the file system. Of
+course as long as there was a copy in the swap area, the file was
+marked busy so it could not be overwritten.  On V7 this meant that
+the file could not be removed either, because busy executables
+could not be removed but this restriction was lifted on BSD releases.
+.Pp
+To replace such executables was a cumbersome process. One had first to
+remove the sticky bit, then execute the binary so that the copy from swap
+was flushed, overwrite the executable, and finally reset the sticky bit.
 .Pp
 Later, on SunOS 4, the sticky bit got an additional meaning for
 files that had the bit set and were not executable: read and write
@@ -90,10 +101,6 @@ and bypass the buffer cache.
 This was typically used on swap files for NFS clients on an NFS
 server, so that swap I/O generated by the clients on the servers
 would not evict useful data from the server's buffer cache.
-.Pp
-.Nx
-currently does not treat plain files that have the sticky bit
-specially, but this behavior might change in the future.
 .Sh BUGS
 Neither
 .Xr open 2