How to enable disk quota that manages the space

We can able restrict Disk space once we enable disk quota which alerts a sysadmin before a user takes too much disk space or a partition becomes full.Quotas can only be created for partitions.Quota is of two types, user and group.If we enable quota of 1 MB is set for the partition /home, then every directory under /home or every user on the system, since each directory in /home represents an user, can use a max of 1 MB.