Quotas on the CS Linux Systems: FAQ


I keep getting this e-mail message about disk space usage on my CS Linux account

Messages such as this go out automatically to every account where disk space usage exceeds the user's quota (more in What are quotas anyway?). If you just ignore them, odds are good that within a week or so you won't be able to create new files in your account. This can result is many problems, some not obviously related to disk-space use.

By far the most common reason for being over quota is the habit many Web browsers have of caching pages you've visited; these caches can be big. So the first thing to try, if you get one of these messages, is to clear browser caches. Our script clear-browser-caches does this for Firefox and Chrome. Run it from a terminal window as follows:

If you're still over quota, read on ...

What are quotas anyway?

They're a mechanism provided by Linux (and other UNIX-like) filesystems for limiting total size of each user's files. (Why do we think we need to do this? see Why quotas anyway??). Every time you create a new file, or make an existing file bigger, the system is supposed to check to make sure total space doesn't exceed whatever limit was set for your account. If it does, you're “over quota”, and you have a grace period of about a week to do something about it -- either delete some files or ask for a larger quota.

What happens if I go over quota and do nothing?

Maybe nothing; if nothing you do with your account runs up against the system's quota enforcement mechanism, everything may seem fine (except of course that you keep getting those warning messages). But if you do anything that does run up against the enforcement mechanism, odds are you'll notice: Ill effects can range from sluggish logins/logouts to losing work when you open a file in a text editor and try to save it. (“The computer ate my homework!”) “Are you over quota?” is one of first questions in troubleshooting otherwise mysterious problems with students' accounts.

How can I be over quota? All I have ...

If you wonder how you can be over quota, when all you (think you) have is a few files for your classes ...

You might be surprised how much space some applications use for hidden files (ones whose path names start with a “.”). Browsers cache previously-fetched pages, GUI applications store configuration and history information, etc., etc.

Also, the trash/recycle bin used the graphical file managers counts as part of your space usage.

How do I find out what's taking up so much space?

Some command-line tools that may be helpful:

Some typical space hogs:

I know what's taking up space; now what?

If it's a hidden directory associated with a GUI application, it's probably safest to remove files using the application itself. For example, if you normally delete files by dragging them to the trash/recycle bin, empty it.

Otherwise you can use either the graphical file manager or command-line tools to remove unneeded files:

If you do the above and are still over quota, see Getting help.

Why quotas anyway?

You may wonder why we do this in the first place; after all, these days disk space is commonly regarded as essentially unlimited. In many situations that's true, and ITS has been pretty generous in providing us with a lot of it, with regular backups too.

But in our setup space for user home directories (accessible from all CS Linux systems) is a shared resource, and if we take no steps to limit anyone's use of it, one careless or greedy user can cause real problems for everyone. (It used to happen regularly; beginning programmers in particular can be careless without necessarily meaning to be.)

(Also, you may have observed already that today's “more than anyone could ever use!” is tomorrow's “not nearly enough”!)

Getting help

Your first point of contact should probably be your instructor or research supervisor, but you can also communicate directly with Dr. Massingill, the department's liaison to ITS and occasional Linux admin. Those warning messages (described in I keep getting this e-mail message about disk space usage on my CS Linux account) are set up so that replies go to her.

Increases in quota are sometimes possible if there's what we consider a legitimate need for it, as for example if you're doing research with a faculty member.