Finding and freeing space.
WHAT df DOES
Shows space per mounted file system.
WHAT THE HUMAN-READABLE OPTION ADDS
Sizes you can read at a glance.
WHAT du DOES
Shows how much space directories use.
WHAT THE USEFUL FORM IS
Summarised, one level deep, human-readable, sorted.
WHY ONE LEVEL
It lets you follow the largest directory downward, rather than printing everything.
WHAT THE USUAL CULPRITS ARE
Logs that never rotated Backups kept indefinitely Temporary files Mail queues Old package caches Sessions and caches from web applications
WHAT A FULL DISK CAUSES
Services failing to start Databases refusing writes Sites returning errors Inability to log in, in severe cases
WHAT TO CHECK BESIDES SPACE
Inodes, which can run out while space remains.
WHAT CAUSES INODE EXHAUSTION
Enormous numbers of very small files, typically sessions or cache.
WHAT TO DO ABOUT A DELETED FILE STILL CONSUMING SPACE
Restart the process holding it open.
WHY THAT HAPPENS
Space is only released when the last process closes the file.
WHAT TO SET UP
Monitoring that warns before the disk is full.
