Detecting prelinking breakage

A long time ago RHEL made a bad decision to have prelink enabled by default. This has caused various forms of hard-to-debug heartache for people including me, as a maintainer of a pyinstaller package. The performance gains are dubious, and it causes problems with ASLR and rpm verify (since binaries are modified post-install). Thankfully I believe it is off by default in new versions of Red Hat.

Here's a quick troubleshooting guide to see if prelinking is causing unexpected modification of your binaries.

First check to see if it is enabled:

grep ^PRELINK /etc/sysconfig/prelink

You can also check to see if the binary itself is prelinked using readelf.

To disable it system-wide set "PRELINKING=no" in /etc/sysconfig/prelink and run /etc/cron.daily/prelink as root.

The symptoms are that the binary changes size and hash, but passes rpm --verify (since verify knows about prelinking). In my case the error message looked like:

Cannot open self /usr/lib64/mybin or archive /usr/lib64/mybin.pkg