
                         HOW TO ENABLE QUOTA ON LINUX
                                       
   
   
   _Last updated: Fri Aug 8 09:45:05 HKT 1997_
   
   
        Preamble: This document is copylefted by Albert M.C. Tam
        (bertie@scn.org). Permission to use, copy, distribute this document for
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        distributed in hope that it will be useful, but WITHOUT ANY WARRANTY,
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        editor / maintainer assumes NO RESPONSIBILITY for errors, or for
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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 bertie@scn.org 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.
