difference between filesystem and mountpoint

[bullz]

HI All,

Very silly question.

What is the difference between filesystem and mountpoint, where do we exactly use the term called “Filesystem” and “Mountpoint”.

* points will be shared at the end without fail.

[Matti_Kurkela]

In abstract sense, a filesystem is "something that has a capacity to hold files and directories". A filesystem might be contained in a disk partition (e.g. /dev/sda1), in a LVM logical volume (/dev/vg00/lvol1) or in a CDROM/DVD (/dev/scd0).

The "root filesystem" is a bit special: it is mounted at the system's root directory (/), and it is usually mounted very early in the system's boot sequence. You usually cannot unmount the root filesystem: if you could do that for some reason, you could not do anything but a system halt/reboot after that.

A mount point is the location where a filesystem's root directory is (or will be) attached to the system's directory hierarchy. The mount point of the root filesystem is always the root directory, /.

Any directory in any filesystem can serve as a mount point for mounting another filesystem: no special preparation is required.

The root directory of the "child" filesystem will overlap the directory of the "parent" filesystem that is used as a mount point. If the mount point directory on the "parent" filesystem contains files, those files will be inaccessible while the "child" filesystem is mounted. (Unless those files are hard-linked to some other location on the parent filesystem... but I digress.)

Unix/Linux sysadmins often talk about filesystems and their mountpoints somewhat interchangeably: for example, "the /usr filesystem" is a shorthand for "the filesystem that is normally mounted at mount point /usr".

Fundamental questions like this are interestingly tricky to answer: please ask for more explanations if I was unclear.

MK

[bullz]

Best explanation. +1

So, can I come to a conclusion that,

/dev/cciss/c0d0p3 3.0G 1.5G 1.4G 52% /usr
/dev/cciss/c0d1p1 133G 3.7G 122G 3% /data1

/usr mountpoint is 52% used.
/data1 mountpoint is 3% used.

Instead of referring it as filesystem?

only i suld use "Filesystem" when the communication related with /dev/cciss/c0d0p3 (or) /dev/cciss/c0d1p1

[Patrick Wallek]

>>So, can I come to a conclusion that,
>>/dev/cciss/c0d0p3 3.0G 1.5G 1.4G 52% /usr
>>/dev/cciss/c0d1p1 133G 3.7G 122G 3% /data1
>>/usr mountpoint is 52% used.
>>/data1 mountpoint is 3% used.
>>Instead of referring it as filesystem?

The best way, in my opinion, to state this would be: The filesystem on disk /dev/cciss/codop3, which is mounted to /usr, is 52% utilized.

It is the filesystem itself that contains the data. The mountpoint could change but where ever you mount it, it would be 52% utilized.

>>only i suld use "Filesystem" when the
>>communication related with /dev/cciss/c0d0p3 (or) /dev/cciss/c0d1p1

Not necessarily. Those are disk devices on which a filesystem has been created.

[Steven Schweda]

> /data1 mountpoint is 3% used.

That would seem to be approximately backward.

ls -l /data1
ls -ld /data1
umount /data1
ls -l /data1
ls -ld /data1

"/data1" is a mount point. It's the point
(a directory in the "/" (root) file system)
where the file system on /dev/cciss/c0d1p1 is
normally mounted.

If you do that "umount" command, then
remember to:
mount /data1

A file system is where the files are stored.
A file system can have a capacity, so it
might be, say, 3% full.

A mount point is where a file system appears
in the great tree of file systems. By
itself, it's a directory. It has no
intrinsic capacity, so it can't get full.

[Hakki Aydin Ucar]

A file system is where the files are stored according to their formats compatible to structure such as in file sizes , inode manipulation, lv attidutes..

A mount point is the created access directory that is compatible for this FS

[Matti_Kurkela]

> The best way, in my opinion, to state this would be: The filesystem on disk /dev/cciss/codop3, which is mounted to /usr, is 52% utilized.

Patrick is demonstrating the most complete and technically accurate form here.

But in common sysadmin work, you typically think about the disk device <-> filesystem relations only when you're setting up the system or changing its disk configuration, or troubleshooting a disk problem. Otherwise, you usually won't need to think about it.

On the other hand, the filesystem <-> mountpoint relation is much more important in everyday use, since it is used to define file locations in a way that is immediately usable for users and application configurations.

Therefore, referring to filesystem by using the name of its mountpoint (e.g. "the /opt filesystem") is a very common and practical shorthand.

The operation to identify a disk device when given the mount point of its filesystem (or vice versa) should be trivial for all Unix sysadmins: just type "mount" and read the list. Or on Linux, use "cat /proc/mounts".

MK

[Steven E. Protter]

Shalom,

A file system sits on top of a mount point.

Thats how I keep it straight. Mount point is just a path.

file system resides elsewhere but is mounted on a mount point.

Examples:

I have a file system called mydata. It was allocated disk on a logical volume vg01/lvol1

It is mounted /dev/vg01/lvol1 /mydata

For some reason I don't like that

umount /mydata

mkdir /oradata
mount /dev/vg01/lvol1/oradata

Same data, same file system really, new mount point.

SEP

[bullz]

Thanx all for you kind help. please post if you have any other view.

[Steven Schweda]

> please post if you have any other view.

Please post a question if something is not
yet clear.