How to know what changes YUM UPDATE is going to apply?

Question

How to know what changes YUM UPDATE is going to apply?

I know you can see the list of packages that are going to be updated, but I'd like to know what detailed changes are going to be aplied in package.

Answer 1

There's no out-of-the-box facility to accomplish this. You would need to write a script to do the following:

1. Run yum update in download-only mode to get the new RPMs
2. For each package which is being updated:
   1. Get the list of files and their MD5s installed by the current RPM
   2. Get the list of files and their MD5s contained in the new RPM
   3. Compare the lists and print any differences (added/removed/changed files)
   4. Print the preun and postun scriptlets in the current RPM
   5. Print the pre and post scriptlets in the new RPM

Answer 2

Run the update on a separate, identical system and then compare the two to see what has changed.

Though, this probably isn't going to help you answer your real question. This probably is the answer:

Yum keeps a complete history of everything it does, with a full rollback capability. To roll back a change, first run:

yum history

You'll see a numbered list of transactions. Find the number corresponding to the transaction you want to revert, and then do:

yum history undo ###

Answer 3

You can query a package with rpm to see its changelog.

rpm -qp --changelog http://example.org/path/to/package-1.1.0-2.x86_64.rpm

Or you can read on Red Hat's page on Security Updates and read the errata for your server version.

For Red Hat Enterprise Linux version 6 you would read this errata.