SUMMARY: how to backout a patch that has a corrupted undo file?

From: Brett Lymn (
Date: Mon Jan 17 2000 - 22:17:12 CST

Yesterday I sent out this message:

        I have a patch that when it was applied /var ran out of room.
At the time this was not much of a concern but I want to re-install
the particular product and I want to clean out the patched prior to
doing so. When I try to backout the patch I get this error message:

pkgadd: ERROR: attempt to process datastream failed
pkgadd: ERROR: unable to unpack datastream

Which, I presume, happens when the undo file is attempted to be
unpacked to replace the patch. Note that I am unconcerned about the
state of the product after backing out this patch, I just want the
system convinced that the patches have been backed out so anything
that it takes to remove the patches is ok by me. I am using Solaris

I got a few responses back. A couple suggested just reloading the
patch but that, unfortunately, does not resave the undo information.
Another suggestion was to copy the undo info from another machine
which was a good suggestion except that the patch that was broken was
unique to my machine so no other machine has the file.

Some things I tried myself was to copy the obsolete.Z file from an
earlier patch as undo.Z (from my reading of the patchrm script this is
what patchrm does anyway when a higher revision patch is removed).
This made backoutpatch happy but when I tried to backout the next
patch I got told there was no save info (this may or may not be true,
I cannot recall). For what it is worth, the undo file is a
package-ised version of the of the files that were changed by the new
patch. When you backout a patch the undo package is applied to
reinstate the old files - in my case running out of disk space munged
the file, I do recall that I cleaned up and reapplied the patch but,
of course, the backout information was stuffed by that time.

In the end I just removed the packages and when I looked the unremoved
patches has disappeared from showrev -p. I had no problems
reinstalling the package and patches.

Hearty thanks to:

 Buddy Lumpkin
 James Kwong
 Scott D. Yelich

Brett Lymn, Computer Systems Administrator, British Aerospace Australia

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