Quota mini-HOWTO
Albert M.C. Tam bertie@scn.org
v0.0, 8 August 1997
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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 RedHat 4.1 running kernel 2.0.27). Users run�
ning older kernels may need to upgrade to a newer kernel version in
order to take advantage of quota. Feel free to send feedbacks or com�
ments to bertie@scn.org if you find an error, or if any information is
missing. I appreciate it.
1. What is Quota?
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.
The idea behind quota is that users are forced to stay under their
disk comsumption limit, taking away their ability to comsume 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
seperately.
2. Current Status of Quota on Linux
Quota support has been integrated into kernel since version 1.3.8x I
heard. Now it is part of the 2.0 release of the Linux kernel. If your
system doesn't support quota, I really recommend an upgrade.
Currently, quota works for ext2 type file system only.
3. Requirements for Using Quota on Linux
3.1. Kernel
The 2.x kernel source is available from
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http://sunsite.unc.edu/pub/Linux/kernel/v2.0
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3.2. Quota software
Depending on the Linux distribution you have, you may, or may not have
the quota softwares installed on your system. If you don't, then
download the quota software source from
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ftp://ftp.funet.fi/pub/Linux/PEOPLE/Linus/subsystems/quota/all.tar.gz.
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4. Quota Setup on Linux - Part I: The Configuration
4.1. Reconfigure your kernel
Reconfigure your kernel and add quota support by typing y to:
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Quota support (CONFIG_QUOTA) [n] y
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4.2. Compile and install the quota softwares
The quota software source is available from
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ftp://ftp.funet.fi/pub/Linux/PEOPLE/Linus/subsystems/quota/all.tar.gz
______________________________________________________________________
4.3. time Modify your system init script to check quota and turn
quota on at boot
Here's an example:
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# 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
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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 at the end of your system init script, or,
if you like, right after the part where file systems are mounted in
your system init script.
4.4. Modify /etc/fstab
Partitions that you have not yet enabled quota normally look something
like:
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/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults 1 1
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To enable user quota support on a file system, add "usrquota" to the
fourth field containing the word "defaults" (man fstab for details).
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/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota 1 1
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Replace "usrquota" with "grpquota", should you need group quota
support on a file system.
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/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,grpquota 1 1
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Need both user quota and group quota support on a file system?
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/dev/hda1 / ext2 defaults 1 1
/dev/hda2 /usr ext2 defaults,usrquota,grpquota 1 1
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4.5. Create quota record "quota.user" and "quota.group"
Both quota record files, quota.user and quota.group, should be owned
by root, and read-write permission for root and none for anybody else.
Login as root. Go to the root of the partition you wish to enable
quota, then create quota.user and quota.group by doing:
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touch /partition/quota.user
touch /partition/quota.group
chmod 600 /partition/quota.user
chmod 600 /partition/quota.group
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4.6. Reboot
Now reboot system for the changes you have made to take effect.
Also note that subsequent partitions you wish to enable quota in the
future only require step 4, 5, and 6.
5. Quota Setup on Linux - Part II: Assigning Quota for Users and
Groups
This operation is performed with the edquota command (man edquota for
details).
I would normally run quotacheck with the flags -avug to obtain the
most updated filesystems usage prior to editing quota. This is just a
personal habit, and not a required step however.
5.1. Assigning quota for a particular user
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:
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Quotas for user bob:
/dev/hda2: blocks in use: 2594, limits (soft = 5000, hard = 6500)
inodes in use: 356, limits (soft = 1000, hard = 1500)
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"blocks in use" is the total number of blocks (in kilobytes) a user
has comsumed on a partition.
"inodes in use" is the total number of files a user has on a
partition.
5.2. Assigning quota for a particular group
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:
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Quotas for group games:
/dev/hda4: blocks in use: 5799, limits (soft = 8000, hard = 10000)
inodes in use: 1454, limits (soft = 3000, hard = 4000)
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5.3. Assigning quota for a bunch of users with the same value
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:
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edquota -p bob `awk -F: '$3 > 499 {print $1}' /etc/passwd`
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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.
5.4. Soft Limit
_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.
5.5. Hard Limit
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.
5.6. Grace Period
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":
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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
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Change the 0 days part to any length of time you feel reasonable. I
personally would choose 7 days (or 1 week).
6. Miscellaneous Quota Commands
6.1. Quotacheck
Quotacheck is used to scan a file system for disk usages, and updates
the quota record file "quota.user" to the most recent state. I
recommend running quotacheck at system bootup, or via cronjob
periodically (say, every week?).
6.2. Repquota
Repquota produces a summarized quota information for a file system.
Here is a sample output repquota gives:
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# 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
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6.3. Quotaon and Quotaoff
Quotaon is used to turn on quota accouting; quotaoff to turn it off.
Actually both files are similar. They are executed at system startup
and shutdown.