Prometheus throwing error on /lost+found/ WAL file directory, but running successfully

Prometheus is working as expected, and successfully scraping metrics.

However, I see in the logs, the following error message:

agent=prometheus component=cleaner msg="unable to find segment mtime of WAL" name=/etc/agent/data/lost+found err="unable to open WAL: open /etc/agent/data/lost+found/wal: no such file or directory

The WAL is stored in /etc/agent/data, and this is being utilized as expected. I’m not sure what the /lost+found/ directory is used for. I’m also not sure the impact of this error.

Does anyone have any insight to the /lost+found/ directory, and this particular error message when files are being created within the higher level etc/agent/data directory?

welcome to the :grafana: community @dlgs!

The lost+found directory is usually created by the OS. For example, if the grafana server wasn’t shut down cleanly the filesystem would write parts of the files that were open at that time to be potentially recovered later.