The idea
Start with read-only observations to establish where a file is, who owns it and whether the filesystem has space. pwd identifies the working directory, ls -l shows basic ownership and permissions, and df reports filesystem usage. A full filesystem differs from a missing file or denied access. Do not grant broad permissions or delete unfamiliar files simply to make an error disappear.
Worked example
An application reports it cannot write a log. The log directory exists, but its filesystem has no free space. Changing permissions will not solve that cause. In a different case, free space is available but the service user lacks write permission; diagnose that separately and use the narrowest approved permission change.
Try it
Create a paper troubleshooting table for missing path, permission denied and no space left. List one read-only observation for each and the evidence that would distinguish them. Explain why recursively granting everyone write access or deleting arbitrary files would be an unsafe first response.