Other tools for all filesystems

Some other tools are also useful for managing filesystems. df  shows the free disk space on one or more filesystems; du  shows how much disk space a directory and all its files contain. These can be used to hunt down disk space wasters.

sync  forces all unwritten blocks in the buffer cache (see section 5.6) to be written to disk. It is seldom necessary to do this by hand; the daemon process update  does this automatically. It can be useful in catastrophies, for example if update  or its helper process bdflush  dies, or if you must turn off power now  and can't wait for update  to run.