Problem statement
What should I do when yum on CentOS 7 starts returning 404 errors?
The usual cause is that the machine is still pointing at mirrors that no longer serve active CentOS 7 metadata. The fix is to switch the repository definitions to a still-usable source and then refresh yum metadata.
For helper.sh users, the safest path is to run the repository switch script first, then validate yum install and only after that continue with package installs or Docker maintenance.
What to check
- Switch old mirror definitions before running yum install again.
- Clear metadata and confirm package search works.
- Treat repository recovery as the prerequisite for all later maintenance.
Parent topic
Keep legacy CentOS 7 hosts installable and maintainable when yum repositories fail, mirrors expire, or Docker data needs to be moved off a crowded disk.