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 /mnt directory, 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 a CD-ROM to 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

The mount command enables you to access your file systems, but on most modern Unix systems, the automount function makes 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 −

Sr.No. Command & Description
1 quota

Displays disk usage and limits for a user of group

2 edquota

This is a quota editor. Users or Groups quota can be edited using this command

3 quotacheck

Scans a filesystem for disk usage, creates, checks and repairs quota files

4 setquota

This is a command line quota editor

5 quotaon

This announces to the system that disk quotas should be enabled on one or more filesystems

6 quotaoff

This announces to the system that disk quotas should be disabled for one or more filesystems

7 repquota

This prints a summary of the disc usage and quotas for the specified file systems