Create a Virtual Mount on Linux.

Sometime you want to create a directory with upper limit on size in linux, this could be to restrict usage of a applicaiton or a user or for any other reason. There is no direct way to set limit on quota/size limit on a direcotry in linux. But as the saying goes, you can do anything on linux.

One common way of having size limit directories is creating a virual mount point. Here are the steps to create Vitual Mount Point. Here are the steps for the same:

• Create a directory for filesystem image mkdir /vdisk
• Create a filesystem on disk, my preferred way is to use fallocate
fallocate -l 100G /vdisk/my_disk.img
  Alternatively you can use dd
dd if=/dev/zero of=/vdisk/my_disk.img
• Create fileystem on the disk image, I use xfs but you can use ex3 or ext4.
  mkfs.xfs /vdisk/my_disk.img
• Create the desired directory to mount the disk.
  mkdir -p /opt/data/my_disk
• Mount the virtual disk.
  mount -t auto -o loop /vdisk/my_disk.img /opt/data/my_disk
  or
  mount -t auto -o loop,rw,usrquota,grpquota /vdisk/my_disk.img /opt/data/my_disk
  If you would like to set user or group quotas.
• Add the mount to /etc/fstab to make it permanent.