<!doctype linuxdoc system>
<article>
<title>Quota mini-HOWTO
<author>Ralf van Dooren <tt/r.vdooren@snow.nl/
<date>v0.5, 2003-08-09
<abstract>
Preamble: This document is written by Ralf van Dooren (r.vdooren@snow.nl).
Original text and setup of this document is copyleft-ed by Albert M.C. Tam, many thanks to him
for this initial mini-HOWTO.
This document is licensed under the GNU Free Documentation License.
Permission to use, copy, distribute this document for non-commercial purposes
is hereby granted, provided that the author's / editor's name and this notice
appear in all copies and/or supporting documents; that this document is not
modified. This document is distributed in hope that it will be useful, but
WITHOUT ANY WARRANTY, either expressed or implied. While every effort has been
taken to ensure the accuracy of the information documented herein, the author /
editor / maintainer assumes NO RESPONSIBILITY for errors, or for damages results
for the use of the information documented herein.
<p>
This document describes how to enable file system quota on a Linux host,
assigning quota for users and groups, as well as the usage of miscellaneous
quota commands. It is intended for users running kernel 2.x (recently tested
on kernel 2.4.21).
<p>
Feel free to send feedbacks or comments to r.vdooren@snow.nl if you find an
error, or if any information is missing. I appreciate it.
</abstract>
<sect>What is quota?
<sect1>What is quota for?
<p>
Quota allows you to specify limits on two aspects of disk storage: the
number of inodes a user or a group of users may possess; and the number of
disk blocks that may be allocated to a user or a group of users.
<p>
The idea behind quota is that users are forced to stay under their disk
consumption limit, taking away their ability to consume unlimited disk space
on a system. Quota is handled on a per user, per file system basis. If there
is more than one file system which a user is expected to create files, then
quota must be set for each file system separately. Various tools are
available for you to administer and automate quota policies on your
system.
<sect1>Current Status of Quota on Linux
<p>
Currently, there are some major changes in the way quota works. There are two
different setups. The tools works the same, but there's a difference in used files. This
document describes the setup and operation of the _new_ quota setup. As the new setup
of quota is not in the regular kernel source, this setup needs some patching. We will describe this
patching and installation of the linuxquota package. If you already have the quota software installed
on your system, you may or may not have to install this patch and package. You can email me if
you have any questions about this. I'll try to include a overview of Linux distro's and it's implications
in a later version of this document.
<sect>Requirements for quota
<p>
<sect1>Kernel
<p>
The 2.x kernel source is available from <url
url="http://www.kernel.org/" name="http://www.kernel.org">
Please use an available mirror close to your location to save bandwidth. If
you have a recent version of tar, you can download the .bz2 compressed file.
Untar the kernel:
<code>
cd /usr/src
tar jxvf /path/to/linux-2.4.21-tar.bz2 - for bzip2 kernel -
tar zxvf /path/to/linux-2.4.21-tar.gz - for gzip kernel -
ln -s /usr/src/linux-2.4.21 /usr/src/linux
</code>
<sect1>Quota software
<p>
Depending on the Linux distribution you have, you may, or may not have
the quota softwares installed on your system. The most recent version of quota
is available through SourceForge and is in active development. You can reach the
homepage of the quota-development at <url
url="http://www.sourceforge.net/project/linuxquota"
name="http://www.sourceforge.net/projects/linuxquota" >.
<sect>Quota setup: installation and configuration
<sect1>Patch the kernel
<p>Download the patch for your kernel at:
<url url="ftp://atrey.karlin.mff.cuni.cz/pub/local/jack/quota/"
name="ftp::/atrey.karlin.mff.cuni.cz/pub/local/jack/quota/" >.
<p>
Choose your kernel version and download the patch(es). Patch your kernel with the 'patch' command. If there is more than 1 patch for your kernel version, be sure to apply the patches in the correct order.
You can use this script ( I assume the downloaded patches are in /tmp/quota/ and the kernel has been untarred to /usr/src/linux) :
<code>
#!/bin/sh
gunzip /tmp/quota/*.gz
cd /usr/src/linux
COUNT=`ls -1 /tmp/quota/*.diff | wc -l`
for I in `seq 1 $COUNT`
do
patch -p1 < /tmp/quota/quota-2.4.21-$I-*.diff
done
</code>
<sect1>Reconfigure your kernel
<p>
Reconfigure your kernel and add quota support.
<p>Via `make menuconfig` or `make xconfig` you can find the option to support quota under the Filesystems-menu. You can specify extra options if you need them, like 32-bit UID support.
<p>Save the configuration and compile the kernel. Make sure the new kernel will be used when rebooting the system.
<sect1>Compile and install the quota softwares
<p>
To be able to use all the features of the new quota system, you'll probably need to download the new quota-package. Download the new quota software via the URL
provided above.
<p>
When downloaded do:
<code>$ gzip -dc <downloaded file> | tar xvf
$ cd quota-tools (or whatever directory the software is put in)
$ ./configure
$ make
$ su
# make install
</code>
<sect1>Modify your system init script to check quota and turn quota on at boot
time
<p>
Here's an example:
<code># Check quota and then turn quota on.
if [ -x /usr/sbin/quotacheck ]
then
echo "Checking quotas. This may take some time."
/usr/sbin/quotacheck -avug
echo " Done."
fi
if [ -x /usr/sbin/quotaon ]
then
echo "Turning on quota."
/usr/sbin/quotaon -avug
fi
</code>
The golden rule is that always turn quota on after your file systems in
/etc/fstab have been mounted, otherwise quota will fail to work. I recommend
turning quota on right after the part where file systems are mounted in your system init script.
<sect1>Modify /etc/fstab
<p>
Partitions that you have not yet enabled quota normally look something
like:
<code>/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults 1 1
</code>
To enable user quota support on a file system, add "usrquota" to the fourth
field containing the word "defaults" (man fstab for details).
<code>/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota 1 1
</code>
Replace "usrquota" with "grpquota", should you need group quota support
on a file system.
<code>/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,grpquota 1 1
</code>
Need both user quota and group quota support on a file system?
<code>/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota,grpquota 1 1
</code>
<sect1>Activate the quota system
<p>
To activate the quota software you have to reboot the system for the changes you have made
to take effect. The new kernel with quota support will be loaded and the startup scripts you've
just created will be executed. At first run, quotacheck will generate the appropiate files to maintain
the quota databases.
<sect1>Add quotacheck to crontab
<p>
Although quota should work with periodical checks, it sometimes helps to run quotacheck periodically, e.g. weekly. Add the following line to your root's crontab:
<code>0 3 * * 0 /sbin/quotacheck -avug
</code>
<sect>Quota setup: tools
<p>
This operation is performed with the edquota command (`man edquota` for details).
<sect1>Assigning quota for a particular user
<p>
Here's an example. I have a user with the login id bob on my system. The
command "edquota -u bob" takes me into vi (or editor specified in my $EDITOR
environment variable) to edit quota for user bob on each partition that has
quota enabled:
<code>Quotas for user bob:
/dev/hda3: blocks in use: 2594, limits (soft = 5000, hard = 6500)
inodes in use: 356, limits (soft = 1000, hard = 1500)
</code>
"blocks in use" is the total number of blocks (in kilobytes) a user has
consumed on a partition.
"inodes in use" is the total number of inodes a user has consumed on a partition.
<sect1>Assigning quota for a particular group
<p>
Now I have a group games on my system. "edquota -g games" takes me into
the vi editor again to edit quota for the group games:
<code> Quotas for group games:
/dev/hda4: blocks in use: 5799, limits (soft = 8000, hard = 10000)
inodes in use: 1454, limits (soft = 3000, hard = 4000)
</code>
<sect1>Assigning quota for a bunch of users with the same value
<p>
To rapidly set quotas for, say 100 users, on my system to the same value
as my user bob, I would first edit bob's quota information by hand, then execute:
<code>edquota -p bob `awk -F: '$3 > 499 {print $1}' /etc/passwd`
</code>
assuming that you are using csh, and that you assign your user UID's starting
with 500.
In addition to edquota, there are 3 terms which you should familiarize
yourself with: Soft Limit, Hard Limit, and Grace Period.
<sect1>Soft Limit
<p>
_Soft limit_ indicates the maximum amount of disk usage a quota user has
on a partition. When combined with grace period, it acts as the border line,
which a quota user is issued warnings about his impending quota violation when
passed.
<sect1>Hard Limit
<p>
Hard limit works only when grace period is set. It specifies the absolute
limit on the disk usage, which a quota user can't go beyond his hard limit.
<sect1>Grace Period
<p>
Executed with the command "edquota -t", grace period is a time limit before
the soft limit is enforced for a file system with quota enabled. Time units
of sec(onds), min(utes), hour(s), day(s), week(s), and month(s) can be used.
This is what you'll see with the command "edquota -t":
<code>Time units may be: days, hours, minutes, or seconds
Grace period before enforcing soft limits for users:
/dev/hda2: block grace period: 0 days, file grace period: 0 days
</code>
Change the 0 days part to any length of time you feel reasonable. I personally
would choose 7 days (or 1 week).
<sect>Miscellaneous Quota Commands
<p>
<sect1>Quotacheck
<p>
Quotacheck is used to scan a file system for disk usages, and updates the
quota record file "aquota.user" to the most recent state. I recommend running
quotacheck at system bootup, and via cronjob periodically (say, every week?).
<sect1>Repquota
<p>
Repquota produces a summarized quota information for a file system. Here
is a sample output repquota gives:
<code># repquota -a
Block limits File limits
User used soft hard grace used soft hard grace
root -- 175419 0 0 14679 0 0
bin -- 18000 0 0 735 0 0
uucp -- 729 0 0 23 0 0
man -- 57 0 0 10 0 0
user1 -- 13046 15360 19200 806 1500 2250
user2 -- 2838 5120 6400 377 1000 1500
</code>
<sect1>Quotaon and Quotaoff
<p>
Quotaon is used to turn on quota accounting; quotaoff to turn it off. Actually
both files are similar. They are executed at system startup and shutdown.
</article>
