How to apply a patch correctly?

Question

I am trying to patch a linux 3.13.7 source tree to 3.13.8 using the patch-3.13.8.xz file. Since the patch file is in xz format, I used the following command to apply it while in the source tree:

unxz -cd ../patch-3.13.8.xz | patch -p1

But I receive:

Reversed (or previously applied) patch detected!  Assume -R? [n]

I have checked man patch for the -R flag and the description makes no sense to me. Can someone please explain what is going on and what I need to do to fix this?

Solution

When patching Linux kernel to the next minor version, you should use incremental patch. For your case, you should patch with patch-3.13.7-8.xz. This will patch your kernel source 3.13.7 to 3.13.8.

Comments

[Admin]

So instead of using unxz -cd ../patch-3.13.8.xz | patch -p1, I can put it in reverse mode with unxz -cd ../patch-3.13.8.xz | patch -p1 -R?

[Admin]

Well, no. You should investigate why the patch you are applying has already been applied. It's usually a sign something is wrong.

[Admin]

I have tries answering yes to all Reversed (or previously applied) patch detected! Assume -R? [n] questions and yet most seem to succeed, but some fail. I haven't actually compiled the source before in this particular tree so I guess it would be Ok to download the new linux 3.13.8 source tree anyway.

[Admin]

Yes, I should have said "why patch thinks the patch has already been applied". Programs can make mistakes.

[Admin]

@Shadur Is this flag to be used with the patch command?

[Admin]

Yes. Basically, it tells patch to do absolutely everything except actually alter the files, so you can see if the patch goes through cleanly.