See BLT.

I have sometimes been confused by the words:

• filesystem
• partition
• directory (or subdirectory)

They can sometimes be correctly used interchangeably, but usually should not be because there are important distinctions.

It might be more correct to describe them as sometimes "pairwise interchangeable" -- filesystem and partition can sometimes be used interchangeably, and partition and directory can sometimes be used interchangeably. However, I can't immediately think of a context where filesystem and directory are (or should be) used interchangeably.

Discussion and examples

Partition and Directory

The thingies denoted by /, /usr, /home, etc. are always directories. Sometimes, if a partition is mounted at that mountpoint, it is also a partition.

Note: / is always a partition, and, in a sense, it can also be considered "the filesystem" for a particular Linux system. So, discussing / may be the one time that filesystem, partition, and directory are all relevant and might appear to be used almost interchangeably, but that would probably indicate some confusion or imprecision by the speaker, leading to confusion in the listener.

Filesystem and Partition

I've been confused about these when talking about hard links. Hard links will work only within the same partition. Sometimes I have said (and I think I've heard others say) hard links work only within the same filesystem, which isn't 100% true. If you remember that each partition must be setup with some type of filesystem, it is easy to see why you might say hard links work only within the same filesystem. It's almost but not quite true -- the most accurate statement is that hard links work only within the same partition.

Filesystem and Directory

If you think in terms of "the filesystem" for a Linux system, then a filesystem includes (sub)directories. But, the filesystem is not a directory or subdirectory.

If you think of a partition having a filesystem type, and remember that a partition must be mounted at a mountpoint which is a directory, I suppose you could say that a particular directory is, for example, an ext2 filesystem. However, I think it's a bad idea and should be avoided. It is better to say that a particular partition is an ext2 filesystem.

More Discussion or Examples?

<later?>

Contributors

• RandyKramer - 15 Jan 2002
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