The df Command

The first way to manage your partition space is with thedf (disk free)command. The commanddf -k (disk free)displays thedisk space usage in kilobytes, as shown below

$df -k
Filesystem   1K-blocks   Used  Available Use% Mounted on
/dev/vzfs    10485760  7836644   2649116 75% /
/devices        0     0      0  0% /devices
$

Some of the directories, such as /devices, shows 0 in the kbytes, used, and avail columns as well as 0% for capacity. These are special (or virtual) file systems, and although they reside on the disk under /, by themselves they do not consume disk space.

Thedf -koutput is generally the same on all Unix systems. HereÖs what it usually includes

You can use the-h (human readable) optionto display the output in a format that shows the size in easier-to-understand notation.

The du Command

The du (disk usage) command enables you to specify directories to show disk space usage on a particular directory.

This command is helpful if you want to determine how much space a particular directory is taking. The following command displays number of blocks consumed by each directory. A single block may take either 512 Bytes or 1 Kilo Byte depending on your system.

$du /etc
10   /etc/cron.d
126  /etc/default
6   /etc/dfs
...
$

The-hoption makes the output easier to comprehend

$du -h /etc
5k  /etc/cron.d
63k  /etc/default
3k  /etc/dfs
...
$

Mounting the File System

A file system must be mounted in order to be usable by the system. To see what is currently mounted (available for use) on your system, use the following command

$ mount
/dev/vzfs on / type reiserfs (rw,usrquota,grpquota)
proc on /proc type proc (rw,nodiratime)
devpts on /dev/pts type devpts (rw)
$

The/mntdirectory, by the Unix convention, is where temporary mounts (such as CDROM drives, remote network drives, and floppy drives) are located. If you need to mount a file system, you can use the mount command with the following syntax

mount -t file_system_type device_to_mount directory_to_mount_to

For example, if you want to mount aCD-ROMto the directory/mnt/cdrom, you can type

$ mount -t iso9660 /dev/cdrom /mnt/cdrom

This assumes that your CD-ROM device is called /dev/cdrom and that you want to mount it to /mnt/cdrom. Refer to the mount man page for more specific information or type mount -h at the command line for help information.

After mounting, you can use the cd command to navigate the newly available file system through the mount point you just made.

Unmounting the File System

To unmount (remove) the file system from your system, use the umount command by identifying the mount point or device.

For example,to unmount cdrom, use the following command

$ umount /dev/cdrom

Themount commandenables you to access your file systems, but on most modern Unix systems, theautomount functionmakes this process invisible to the user and requires no intervention.

User and Group Quotas

The user and group quotas provide the mechanisms by which the amount of space used by a single user or all users within a specific group can be limited to a value defined by the administrator.

Quotas operate around two limits that allow the user to take some action if the amount of space or number of disk blocks start to exceed the administrator defined limits

• Soft Limit  If the user exceeds the limit defined, there is a grace period that allows the user to free up some space.
• Hard Limit  When the hard limit is reached, regardless of the grace period, no further files or blocks can be allocated.

There are a number of commands to administer quotas