After installing the epel-release package on CentOS 7, running yum updateinfo would hang due to a bug where DNF failed to open files in /var/cache/dnf/. Removing the epel-release package resolved the issue.

1. DNF - Failed to open: /var/cache/dnf/ - CentOS 7
Overview
After installing “epel-release” package; when you run “yum updateinfo” its hung.
Applies To
CentOS 7
Error Message
Failed to open:
/var/cache/dnf/x86_64/7/x86_64/7/epel/repodata/f0ba540170d9c6246d7a6681c9e6d0a6a33b4c9cd04
3ba0478d2a6b6a8d7c197-updateinfo.xml.bz2.
Cause
It’s a known issue and bug in CentOS 7. To get more information about this bug, check the url;
https://bugs.centos.org/view.php?id=9339
Resolution
To resolve this issue, remove “epel-release”.

2. DNF - Failed to open: /var/cache/dnf/ - CentOS 7
Verify DNF
After removing the package, run the command again.