Obtain a rescue CD.

Hopefully the machine is still up and running, or can get to that point, so do the following:

df -hP

and note the device your problematic mount is located on.

devtmpfs        1.9G     0  1.9G   0% /dev
tmpfs           1.9G     0  1.9G   0% /dev/shm
/dev/sda3        96G  4.8G   91G   5% /
/dev/sda1      1014M  224M  791M  23% /boot

For example, let's assume it is /dev/sda3

Now follow steps in https://www.golinuxcloud.com/e2fsck-repair-filesystem-in-rescue-mode-ext4/

This did not work…had to reinstall operating system.

Other notes:

https://microdevsys.com/wp/corruption-warning-metadata-has-lsn-649052-ahead-of-current-lsn-649006-please-unmount-and-run-xfs_repair-v4-3-to-resolve/