Hi Team ,

Team Can any give me a good explanation of mount file system.if we have do a df -k it show /var/orcl/abc/txt mounted on /var/orcl.

example :

Filesystem 1K-blocks Used Available Use% Mounted on
tmpfs 4021876 0 4021876 0% /dev/shm

Kindly explain me what does Filesystem,Mounted on Means in the above example .


Thanks,
Anudeep

The first field shows the type of the filesystem. "tmpfs" is a virtual filesystem that uses a portion of your RAM[*]. So it's extremely fast (but volatile).

The second field shows how big the filesystem is: 4021876 * 1kB, so about 4GB. Be careful: this does NOT mean that the filesystem blocks are actually 1kB each. You told df to show dimension in 1k blocks, using the "-k" option.

Third field shows the number of used (1k) blocks. 0 means that the fs is empty.

Fourth field shows the number of available (1k) blocks. In your example, all blocks are empty and available.

Fifth field shows the how much the filesystem is used, in percentage. Again, 0% means empty.

Last field shows the mount point of this filesystem. This tmpfs filesystem is mounted on /dev/shm, which is a directory on your primary filesystem (that is on your root partition). Even if this directory is not empty on the disk (however any mountpoint should be empty), as long as another filesystem is mounted on it you can't see (nor access to) the content of this directory on the disk: you will see the content of the mounted filesystem instead.

If you write, for instance, to /dev/shm/filetest, you're not writing to one of your disks, but to your virtual filesystem in RAM.

Try:

dd if=/dev/zero of=/dev/shm/filetest bs=16M count=50

Do you mind telling us on what platform and OS? I have doubts about your df -k output...
And next time use code tags and not fancy colors that doesnt help the search engines...