Diagnosing resource consumption.
DISK SPACE
df -h shows usage by filesystem, which tells you whether you have a problem. du identifies which directories are largest. Working down from the root, largest first, finds the culprit quickly.
Common findings: unrotated logs, local backups, package caches, session files, mail spool, database growth.
Watch for deleted files still held open by a process. The space is not released until the process is restarted, and du will not show it while df reports the disk full.
INODES
df -i reports inode usage. A filesystem can exhaust inodes while showing free space, usually from very many small files: sessions, cache, or mail.
MEMORY
free shows the overall picture. Look at available rather than free. top or htop sorted by memory shows which processes consume most.
Common findings: too many PHP-FPM processes, a database buffer pool set too large, or a memory leak in an application.
THE PATTERN
Identify the largest consumer, understand why, then act. Deleting blindly to free space usually removes the wrong thing.
