virtualfs_with_acl_quota.md

Creating a Virtual Filesystem where acl and quota are switched on

This description is based on the following links: https://thelinuxexperiment.com/create-a-virtual-hard-drive-volume-within-a-file-in-linux/ http://linuxgazette.net/109/chirico.html http://stackoverflow.com/a/8148831 http://www.tecmint.com/set-access-control-lists-acls-and-disk-quotas-for-users-groups/

Step 0 - Preparing

# sudo apt install quota
# mkdir -p /var/diskimg

Step 1 - Creating an 100GB regular file (as a disk image) with all zeros:

# dd if=/dev/zero of=/var/diskimg/virtfs.img bs=1M count=100000

Comment: dd uses a block size of 512 bytes by default and we can change to 1M.

Step 2 - Formating the previous file as an ext4 filesystem:

# mkfs -t ext4 /var/diskimg/virtfs.img

Step 3 - Mounting this filesystem to /srv via loop device, setting up acl and quota:

# mount /var/diskimg/virtfs.img /srv -t auto -o usrquota,grpquota,acl,loop=/dev/loop3

Step 4 - Switching on quota for users and groups:

# quotacheck -mcuvgf /srv
# quotaon -vu /srv
# quotaon -vg /srv

Comment: the quotacheck scans a filesystem for disk usage, create, check and repair quota files. (The switch -f forces checking and writing of new quota files on filesystems with quotas enabled.)

Step 5 - Setting quota to 10G for a user (with $uid)

# setquota -u $uid 10G 10G 0 0 /dev/loop3

Comment: the format (after $uid) is block-softlimit block-hardlimit inode-softlimit inode-hardlimit. To disable a quota, set the corresponding parameter to 0.