invalid predicate

I do a lot of packaging for RHEL/CentOS 5 hosts, often this packaging is backporting of newer software versions, typically I’ll pull Fedora’s latest package and make various adjustments to it for RHEL 5’s older environment – typically things like package name changes, downgrade from systemd to init and correcting any missing build dependencies.

Today I came across this rather unhelpful error message:

+ /usr/lib/rpm/ /usr/src/redhat/BUILD/my-package-1.2.3
find: invalid predicate `'

This error is due to the newer Fedora spec files often not explicitly setting the value of BuildRoot which then leaves the package to install into the default location, which isn’t always defined on RHEL 5 hosts.

The correct fix is to define the build root in the spec file with:

BuildRoot: %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)

This will set both %{buildroot} and $RPM_BUILD_ROOT, so no matter whether you’re using either syntax, the files will be installed into the right place.

However, this error is a symptom of a bigger issue – without defining BuildRoot, the package will still compile and complete make install, however instead of the installed files going into /var/tmp/packagename…etc, the files will be installed directly into the actual / filesystem, which is generally ReallyBad(tm)

Now if you were building the package as a non-privileged user, this would have failed at the install phase and you would not have gotten as far as the invalid predicate error.

But if you were naughty and building as the root user, the package would have installed into / without complaint and clobbered any existing files installed on the build host. And the first sign of something being wrong is the invalid predicate error when the find debug script gets provided with no files.

This is the key reason why you are highly recommended to build all packages as a non-privileged user, so that if the build incorrectly tries to install anything into /, the install will be denied and the user will quickly realize things aren’t installing into the right place.

Building as root can be even worse than just “whoops, I overwrote the installed version of mypackage whilst building a new one” or “blagh annoying invalid predicate error” – consider the following specfile line:

rm -rf $RPM_BUILD_ROOT/%{_includedir}

On a properly defined package, this would execute:

rm -rf /var/tmp/packagename/usr/include/

But on a package lacking a BuildRoot definition it becomes:

rm -rf /usr/include/

Yikes! Not exactly what you want – of course, running as a non-root user would save you, since that rm command would be refused and you’d quickly figure out the issue.

I will leave it as an exercise of the reader to determine why I commented about this specific example… ;-)

IMHO, rpmbuild should be patched to just outright refuse to compile packages as the root user so this mistake can’t happen, it seems silly to allow a bad packaging habit to be used when the damages are so severe.

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2 Responses to invalid predicate

  1. Jethro Carr says:

    Oh and if you do something really stupid like blow away /usr/include, remember that rpm -qa will provide a full list of installed packages and it’s pretty simple to then grep the ones you want and do a yum reinstall packagenameshere to get the lost files back.

    Of course you have backups you could fall back too… right? :-P

  2. saberworks says:

    Thanks for this, extremely useful. It’s one of those errors I could get stuck on for a long time and your post explains it in a way that is easy to understand.

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