When installing repmgr3 package on a CentOS 6 64 bits, I always end up with an error at postinstall saying that /var/run/repmgr doesn't exist.
Here is a patch that will hopefully fix that. (The patch deals with all distro for 9.4 release. I didn't check other releases.)
I worked a bit more with repmgr. I found that the initscript doesn't respect the $user variable all the time. Hence this new patch (which includes the changes from the first patch).
I'm also wondering why we do have this new OS user (repmgr). It seems to be more a burden than anything else. Actually, they have a much better initscript in upstream that makes use the postgres OS user. The RPM package should embrace that change.