Page 179 - DCAP602_NETWORK_OPERATING_SYSTEMS_I

Unit 10: File System

mounted medium (hard disk or partition of a hard disk, CD, DVD, flash card, USB or other notes
storage device).
During system startup, all the partitions are thus mounted, as described in the file /etc/fstab.
Some partitions are not mounted by default, for instance if they are not constantly connected to
the system, such like the storage used by your digital camera. If well configured, the device will
be mounted as soon as the system notices that it is connected, or it can be user-mountable, i.e. you
don’t need to be system administrator to attach and detach the device to and from the system.
On a running system, information about the partitions and their mount points can be displayed
using the df command (which stands for disk full or disk free). In Linux, df is the GNU version,
and supports the -h or human readable option which greatly improves readability.

Note Commercial UNIX machines commonly have their own versions of df and
many other commands. Their behavior is usually the same, though GNU versions of
common tools often have more and better features.

The df command only displays information about active non-swap partitions. These can include
partitions from other networked systems, like in the example below where the home directories
are mounted from a file server on the network, a situation often encountered in corporate
environments.

> df -h
Filesystem Size Used Avail Use% Mounted on
/dev/hda8 496M 183M 288M 39% /
/dev/hda1 124M 8.4M 109M 8% /boot

/dev/hda5 19G 15G 2.7G 85% /opt
/dev/hda6 7.0G 5.4G 1.2G 81% /usr
/dev/hda7 3.7G 2.7G 867M 77% /var
fs1:/home 8.9G 3.7G 4.7G 44% /.automount/fs1/root/home
10.1.3 network file systems

The Network File System (NFS) was originally developed by SUN Microsystems as a protocol
that allowed communications between different computing environments. The NFS enables a
Linux workstation to mount an exported share from the server into its own filesystem, thus
giving the user and the client the appearance that the sub filesystem belongs to the client; it
provides a seamless network mount point.
NFS consists of at least two main parts: a server and one or more clients. The client remotely
accesses the data that is stored on the server machine. In order for this to function properly a few
processes have to be configured and running.
The server has to be running the following daemons:

Daemon Description
nfsd The NFS daemon which services requests from the NFS clients.
mountd The NFS mount daemon which carries out the requests that nfsd passes on to it.
rpcbind This daemon allows NFS clients to discover which port the NFS server is using.

LoveLy professionaL university 173