Language Selection

English French German Italian Portuguese Spanish

Custom scripting gives users a safe-du

Filed under
HowTos

My company has a Linux cluster with a terabyte of attached storage. Over time we noticed the head node was becoming more overloaded. Inspection of the system showed that users were starting dozens of copies of the du utility to determine disk space usage. This was a natural thing for them to do, because they had a need to know how much disk space was available. A lack of disk space would cause their software builds and tests to fail. The problem was that it takes five to seven hours for a du of the entire shared filesystem. Thus, when the filesystem was nearly full (as it of course usually was), the number of du processes would increase almost exponentially.

To address this problem, we first set up automated nightly disk space reports, so that users could check the status without running du. This still did not solve the problem, as the amount of used space could fluctuate dramatically over the course of 24 hours. Users still wanted and needed to run their own du processes throughout the workday.

While adding more disk space would have solved the problem, we are using a large disk array that is already filled to maximum capacity. In general, users tend to fill up all available disk space anyway, no matter how much you give them.

We then developed a policy: users could run du on any directory they owned. In addition, user du processes would be allowed to run for a maximum of one hour of wall time. Users in the wheel group would be exempt from these restrictions.

I was given the task of developing a tool to implement this policy. Some sort of wrapper around the existing du seemed like an obvious choice: the script could validate the input, abort if an invalid path was given, and terminate the du process if it ran too long.

I wrote a basic bash script in perhaps an hour's time. Then I thought about how to run it, and that is where I ran into trouble. I had thought that I would make the script set user id (setuid) or set group id (setgid) root, i.e. when run by any user it would actually run in the root group. Then, I could change the permissions on the real du so that only root could run it. The result would be that normal users could only access the real du through the wrapper script.

Of course that would make a pretty boring article, and in reality it didn't turn out to be that simple:

Full Story.

More in Tux Machines

today's leftovers

US Military To Launch Open Source Academy

Open source software, which has become increasingly common throughout the US military from unmanned drones to desktops, has now been enlisted as a career option for military personnel. In September, Camp Shelby Joint Forces Training Center will open a Linux certification academy, marking the first time such a training program has been hosted on a military base. Read more

Video: TedX talk - Richard Stallman

Well, vp9/opus in a webm container have been supported by both Firefox and Google Chrome for several releases now... so enjoy it in your web browser. Read more

Eclipse Luna for Fedora 20

If you are a Fedora Eclipse user, then you're probably saddened since the release of Eclipse Luna (4.4) because you are still using Eclipse Kepler (4.3) on Fedora 20. Well, be saddened no longer because Eclipse Luna is now available for Fedora 20 as a software collection! A software collection is simply a set of RPMs whose contents are isolated from the rest of your system such that they do not modify, overwrite or otherwise conflict with anything in the main Fedora repositories. This allows you install multiple versions of a software stack side-by-side, without them interfering with one another. More can be read about this mechanism on the software collections website. The Eclipse Luna software collection lives in a separate yum repository, which must be configured by clicking on this link to install the release package. Read more