Controlling Linux disk space usage using quotas

If you're managing a system with multiple users, but finite disk resources, you might want to set limits for how much disk space will be allowed to individual users, or even groups. This can be helpful if some of your team members are in the habit of downloading hundreds of cute kitten videos from YouTube, or if you're worried that certain processes might automatically generate huge log files. You can manage limits using the Quota tool.

First of all, you'll need to make sure that Quota is actually installed on your system, on my Fedora Distribution, it is.

Next, we would edit the /etc/fstab file to add quota options to each filesystem. In our case, we've already added user quota and group quota to enable quotas for both users and groups to the filesystem mounted to /home. The easiest and surest way to have these changes take effect is to reboot the system. Since we didn't actually change anything this time, we can obviously skip that step. To build a table of the current disk usage on our filesystem, update the disk quota files, and if necessary, create the aquota.group and aquota.user files, we would run quotacheck -avmug. A = all, M will force a check on mounted file systems, U and G will check users and groups, and V = verbose.

Quota isn't actually switched on out of the box. We'll run quotaon -av, where A stands for all, and V for verbose, to start it up. Let's use repquota which stands for report quota to take a look at what's going on. We can see that there are currently only two users being monitored by quota, root and my user. In fact, there are currently no other user accounts in the system. We can also see there are two different kinds of limits, blocks and files. Quota allows you to apply limits using either metric.

A hard limit acts like a solid wall, if a user would try to create a file that pushes him over his limit, the operation will simply fail. A soft limit will allow the operation to succeed, but will only allow the excess data to survive for a specified time, which by default is seven days. The value 0 means that there are currently no limits on this account. We can edit the limits allowed to a user or group using edquota -u to edit a user's quota, or edquota -g to edit a group's quota. Let's run this on my own account, not that I would ever seriously consider cutting back on my consumption of cute kitten videos, mind you.

We'll run edquota -u as sudo. We've actually been dropped into the text editor Vi, and I'm sure that now you're really happy you paid attention during the Vi video in the previous course. We can hit the I key to enter insert mode, so we can edit a value. I could create a real limit, either through the block or inode, meaning file. For now, I'll just hit escape and then colon and Q to exit. You can edit the soft limit grace period using edquota -t, again you can control the grace period for both block and inode limits.

Let's review. Quota allows you to impose limits on the amount of disk space users or groups can consume. Once you've applied Quota configuration to each of the relevant filesystems using fstab, quotacheck will build the environment you need to get started. Quotaon will enable quota controls, quotaoff will disable controls, repquota will print a report of the current quota status of each user and group, edquota -u will let you edit a user's profile, edquota -g will do the same for a group, and edquota -t lets you edit the length of your soft limit grace period.