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LPI Linux Certification/Managing Disk Quota

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Detailed Objective

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Weight: 1

Description:
Candidates should be able to manage disk quotas for users.

  • Key knowledge area(s):
    • Set up a disk quota for a filesystem.
    • Edit, check and generate user quota reports.
  • The following is a partial list of the used files, terms and utilities:
    • quota
    • edquota
    • repquota
    • quotaon

Quotas

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On a system, root can manage the usage of disk space per user and per filesystems. The two limits that can be setup are: The soft limit (soft =) specifies the maximum amount of disk usage a quota user is allowed to have. The hard limit (hard =) specifies the absolute limit on the disk usage a quota user can't go beyond it. There is also the possibility to setup a grace period that will enforce the soft limit only after an amount of time specified.

Setting up quotas for users

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1) The keyword usrquota or/and grpquota must be added in file /etc/fstab for the partition interested. 

/dev/fd0  /home/yann/mnt auto    rw,noauto,user,usrquota 0 0
/dev/hda5 /home     ext2    defaults,usrquota,grpquota 1 2

2) Add in each root filesystems the file user.quota or/and group.quota. 

touch /mnt/aquota.user
touch /home/aquota.user
touch /home/aquota.group 
chmod 600  /mnt/aquota.user 
chmod 600  /home/aquota.user 
chmod 600  /home/aquota.group

Only root can do the quota administration and once the empty files have been created some disk quota can be set such as:

  • Soft limitation on number of files and inodes.
  • Hard limitation on number of files and inodes if the grace time is set.

Setting up quotas for users

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3) Check the setting 

quotacheck -v mnt
quotacheck: Scanning /dev/fd0 [/home/yann/mnt] done
quotacheck: Checked 6 directories and 1 files

4) Enable quota on the disk 

quotaon -av
/dev/fd0 [/home/yann/mnt]: user quotas turned on

5) Customize the disk quota limits: 

$ edquota -u yann
Disk quotas for user yann (uid 500):
Filesystem    blocks       soft       hard     inodes     soft     hard
/dev/fd0       15          0          0          4        0        0

$ edquota -g yann 

$ edquota -t
Grace period before enforcing soft limits for users:
Time units may be: days, hours, minutes, or seconds
Filesystem             Block grace period     Inode grace period
/dev/fd0                      7days                  7days

List quotas

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To list quotas for an user or group, use quota. 

quota [options] [user|group]

Common options:

-u:Default, print user quotas.
-g:Print group quotas for the group of which the user is a member.
-q: Print a more terse message, containing only information on filesystems where usage is over quota.

Example: 

quota -u yann

Display a quota report

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To display a quota report, use repquota. 

repquota [options] [user|group]

Common options:

-a: Report on all filesystems indicated in /etc/mtab to be read-write with quotas.
-g: Report for group.

Example: 

$ repquota /dev/fd0
*** Report for user quotas on device /dev/fd0
Block grace time: 7days; Inode grace time: 7days
                Block limits                   File limits
User            used    soft    hard  grace    used  soft  hard  grace
----------------------------------------------------------------------
root   --       8       0       0              2     0     0
yann   --      15       0       0              4     0     0

Exercises

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  1. Setup a soft limitation for any users that have their home directory in /home to 500M.
  2. Change the grace time to 0.
  3. Log as the user and check if the limitation works.


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