HOW TO ENABLE QUOTA ON LINUX



  _Last updated: Fri Aug 8 09:45:05 HKT 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
  running older kernels may need to upgrade to a newer kernel version in
  order to take advantage of quota.

  Feel free to send feedbacks or comments to [email protected] if you find
  an error, or if any information is missing. I appreciate it.


    _________________________________________________________________



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.

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.

Requirements for Using Quota on Linux



  _Kernel_

  The 2.x kernel source is available from

  http://sunsite.unc.edu/pub/Linux/kernel/v2.0



  _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

  ftp://ftp.funet.fi/pub/Linux/PEOPLE/Linus/subsystems/quota/all.tar.gz.





    _________________________________________________________________



Quota Setup on Linux - Part I: The Configuration



  _1. Reconfigure your kernel_

  Reconfigure your kernel and add quota support by typing y to:


    Quota support (CONFIG_QUOTA) [n] y



  _2. Compile and install the quota softwares_

  The quota software source is available from

  ftp://ftp.funet.fi/pub/Linux/PEOPLE/Linus/subsystems/quota/all.tar.gz



  _3. Modify your system init script to check quota and turn quota on at
  boot time _

  Here's an example:


       # 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



  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. Modify /etc/fstab_

  Partitions that you have not yet enabled quota normally look something
  like:


       /dev/hda1       /       ext2    defaults        1       1
       /dev/hda2       /usr    ext2    defaults        1       1



  To enable user quota support on a file system, add "usrquota" to the
  fourth field containing the word "defaults" (_man fstab_ for details).



       /dev/hda1       /       ext2    defaults        1       1
       /dev/hda2       /usr    ext2    defaults,usrquota       1       1



  Replace "usrquota" with "grpquota", should you need group quota
  support on a file system.


       /dev/hda1       /       ext2    defaults        1       1
       /dev/hda2       /usr    ext2    defaults,grpquota       1       1



  Need both user quota and group quota support on a file system?


       /dev/hda1       /       ext2    defaults        1       1
       /dev/hda2       /usr    ext2    defaults,usrquota,grpquota       1
 1



  _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:


       touch /partition/quota.user
       touch /partition/quota.group
       chmod 600 /partition/quota.user
       chmod 600 /partition/quota.group



  _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.

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.

  _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:


       Quotas for user bob:
       /dev/hda2: blocks in use: 2594, limits (soft = 5000, hard = 6500)
               inodes in use: 356, limits (soft = 1000, hard = 1500)



  "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.

  _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_:


       Quotas for group games:
       /dev/hda4: blocks in use: 5799, limits (soft = 8000, hard = 10000)
               inodes in use: 1454, limits (soft = 3000, hard = 4000)



  _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:


       edquota -p bob `awk -F: '$3 > 499 {print $1}' /etc/passwd`



  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.

  _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.

  _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_.

  _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":


       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



  Change the 0 days part to any length of time you feel reasonable. I
  personally would choose 7 days (or 1 week).


    _________________________________________________________________



Miscellaneous Quota Commands



  _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?).

  _Repquota_

  Repquota produces a summarized quota information for a file system.
  Here is a sample output repquota gives:


       # 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



  _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.

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