Having an ext4 filesystem on dev, register the quota in /etc/fstab:
devmountpointext4 defaults,usrquota 0 0
mount -o remount mountpoint
quotaon -a
quotacheck -v dev -f
quotacheck: Scanning dev [mountpoint] done
quotacheck: Old group file name could not been determined. Usage will not be subtracted.
quotacheck: Checked 2 directories and 1 files
quotatool -u user -bq 500M -l '600 Mb' mountpoint
To see if it works and how much space is in use:
repquota mountpoint
*** Report for user quotas on device dev
Block grace time: 7days; Inode grace time: 7days
Block limits File limits
User used soft hard grace used soft hard grace
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me -- 20 1000m 30000m 3 0 0