• First install the quota tools

# apt-get install quota libquota-perl

• Then, enable the quota kernel module

# modprobe quota_v2

• Enable quota on /data partition

# /dev/md2        /data   ext4    defaults,grpjquota=aquota.group,jqfmt=vfsv0       0       0

• remount partition

# mount -o remount /data

• Generate quota files

# quotacheck -cmg /data
# chmod 600 /data/aquota.*

• Enable quota

# quotaon /data