隔几个小时，就有如下的告警

Aug  5 05:44:14 db dnf[356416]: Unable to read consumer identity
Aug  5 05:44:14 db dnf[356416]: This system is not registered with an entitlement server. You can use subscription-manager to register.
Aug  5 05:44:14 db dnf[356416]: CentOS Linux 8                                  0.0  B/s |   0  B     00:00
Aug  5 05:44:14 db dnf[356416]: Errors during downloading metadata for repository 'InstallMedia':
Aug  5 05:44:14 db dnf[356416]:  - Curl error (37): Couldn't read a file:// file for file:///mnt/BaseOS/repodata/repomd.xml [Couldn't open file /mnt/BaseOS/repodata/repomd.xml]
Aug  5 05:44:14 db dnf[356416]: Error: Failed to download metadata for repo 'InstallMedia': Cannot download repomd.xml: Curl error