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Faculty of Mathematics

Home Directory Quotas and Disk Space

Overview

We operate disk quotas on home directories. The default quota for new users is 3GB (for short-term visitors here for less than 1 month it is 500MB). Home directory space is for important files that should be backed up.

When your disk usage reaches your quota you will not be able to save any more files in your home directory, nor update existing files.

The main reason we have disk quotas is because of backups. We regularly backup your files and there is a limit to how much data can be backed up with the resources we have. Quotas also substantially reduce the likelihood of the home directory storage suddenly filling up and causing problems for everyone.

Users of the Maths Linux Gnome (or KDE) desktops will have a small applet running to display quota information in a small region of the screen. On Gnome this will usually be near the top right of the screen, and on KDE near the bottom right.

On Linux the monitor shows a percentage as text and has a blue area indicating usage. The blue will rise to fill the box when you have run out of space. Hovering the mouse over the applet or clicking on it will display more quota/usage information.

Linux quota applet

Windows users have had a similar quota monitor for some time in the status region to the bottom right of the screen.

Windows quota applet

All of these quota monitors will alert you when you are close to running out of space and allow you to quickly check your usage levels.

From the Linux command line you can check your quota at any time with the command quota.

Alternative places to store your data

If you are running close to your limit consider other ways of storing data. Be aware that most of the following locations will not be backed up unless you make your own arrangements for this.

How to cut down

Files in your Wastebasket (aka Trash, Recycle Bin) count towards your quota, so emptying the Wastebasket is the first thing to try if you are running out of quota.

Spam can take up a great deal of space if it is automatically filtered into a separate folder so that you don't notice it. Ensure that you empty your "spam" or "Junk Email" folder regularly. If you haven't checked it for a while, make sure that no real email has sneaked in before deleting the folder.

Large or infrequently accessed files can be compressed with bzip2 (and uncompressed with bunzip2). Directories can be turned into a compressed archive with the tar command:

# To archive and delete the directory dirname
tar cjvf dirname.tar.bz2 dirname && rm -rf dirname

# To extract the archive dirname.tar.bz2
tar xjvf dirname.tar.bz2

Finding the big files

To see how much space you are using you can run, from your home directory:

  du -sk * .??* | sort -n

That will show you how much space each file and directory in your home directory is using, with the largest ones at the end. If you find a large directory you can cd into it and run the command again, and repeat as many times as needed to locate your large files.

Or use baobab and click "Scan Home" to see the same data in a graphical format.

If you are having difficulty tracking down the large files in your home directory space, a command like:

  du -ak > /tmp/du-$LOGNAME; sort -n /tmp/du-$LOGNAME

will list all the files and folders/directories in your home directory, and sort them by size from smallest to largest. Run this command from your home directory. It may take quite some time to display the files.

The command given above stores the results of the du -ak in a file in /tmp/ so you can examine it several times to look for several large files.

To find large files which haven't been accessed in a while:

find ~/ -type f -size +4096k -atime +100 -ls

This will find all files larger than 4MB and not read in over 100 days. These numbers can be changed for various situations remembering that 1 Meg = 1024k.

To check just the files in the top level of your home directory you could run:

  cd $HOME; ls -sa1 | sort -n

This will list your files sorted by size, but won't look in any directories/folders.

Quota policy and requests for an increase

If the home directory storage becomes completely full then lots of computing and IT services will stop working or behave erratically. If the home directories become too large for our backup system then the frequency of backups will have to be reduced.

Home directory space is expensive (reliable, fail-over, fast, backups of various types including snapshots, archive, offline and offsite, etc.) and a shared resource.

The default home directory quota is 3GB. Each request for a quota increase is judged on a case by case basis with the aim of balancing:

  • needs of all users (10% of user accounts should not be able to completely fill the home directory service)
  • need of the account holder for space in which to store important data
  • fairness between user accounts

To request a quota change please email help@maths with:

  • how much you want your quota to change by (increase/decrease)
  • why you need a quota change

Useful links