From: davidsen@ariel.crd.GE.COM (william E Davidsen) Subject: Re: FOLLOWUP: fileutl-3.3B* and find-3.7B*: possible problems Date: 29 Jul 1992 19:44:01 GMT
In article <14203@borg.cs.unc.edu>, faith@cs.unc.edu (Rik Faith) writes:
|
| This note explains the problems that I was having with fu-3.3's cp, what
| caused these problems, and why cp is really *SAFE*!
|
| The only documented problem with fu-3.3's cp involves cp'ing a kernal image
| for booting with shoelace (i.e., cp Image /vmunix). The cp in 3.3, since I
| compiled it with a kernel that has st_blocks working correctly (i.e., 0.96c
| pl2) is now able to detect when a file has "holes" in it. It will then try
| to copy the "holes." It does this during the copy by looking for a block of
That's a great feature in general, although I can see where it could
cause problems in some cases.
| However, shoelace *CANNOT* correctly read a file that contains "holes."
|
| So, I had two *IDENTICAL* kernel images, one created with a new cp and one
| created with an old cp. They were identical in terms of size, sum, and diff.
| One would boot and the other would not. This seemed very weird, and since
| a new utility that I has posted was involved, I decided to err on the side
| of caution and post a retraction message (especially since I had made some
| optimizations in the compilation of the posted binaries). It now seems that
| this was not necessary, and that the files that I posted are *SAFE*.
This sounds like a responsible thing to do, and I either a note in the
man page of a command line option. I wish there were a better way to
tell what's "really" in the file.
I have my own "kopy" routine which does the same thing, for database
use. And a backup utiltiy which detects and eliminates zero block during
saves to keep backup media usage down. Great feature.
We could probably start a thread in comp.arch.storage about the
benefits of having this in the kernel.
--
bill davidsen, GE Corp. R&D Center; Box 8; Schenectady NY 12345
It never ceases to amaze me that otherwise rational people, able to
understand calculus, compound interest, and the income tax form, can
continue to believe that poker is a game of chance.