q42-disk-quotas

Énoncé§

Solve this question on: data-001

1. Enable user and group quotas on the /home filesystem.
2. Set user alice a soft limit of 500M and a hard limit of 1G for blocks; soft 1000 and hard 2000 files (inodes).
3. Set the same defaults for any new user via the prototype technique.
4. Write the current quota report for /home into /opt/course/42/quota-report.

Solution§

Install the tools§

sudo apt install quota         # Debian
sudo dnf install quota         # RHEL

Step 1 — Enable quotas on the filesystem§

Edit /etc/fstab for the target filesystem:

UUID=...  /home  ext4  defaults,usrquota,grpquota  0 2

Re-mount or apply:

sudo mount -o remount /home
mount | grep /home          # confirm options

XFS uses mount options at mount time instead of quotacheck:

• uquota, gquota, pquota — enforce
• uqnoenforce, etc. — accounting only

For ext4 (or older filesystems) you must initialise the quota DB:

sudo quotacheck -cugm /home
# generates /home/aquota.user and /home/aquota.group
sudo quotaon -v /home
sudo quotaoff -v /home          # disable

Step 2 — Set limits for a user§

Interactive editor:

sudo edquota -u alice

Block sizes are in KB:

Filesystem  blocks  soft   hard   inodes  soft  hard
/dev/vda2   3200    512000 1048576 145     1000  2000

Or non-interactively with setquota:

sudo setquota -u alice 512000 1048576 1000 2000 /home
# soft-blk  hard-blk  soft-inode  hard-inode

For a group:

sudo setquota -g devs 5G 10G 0 0 /home

Soft vs hard limits + grace period§

• Soft — can be exceeded temporarily during the grace period.
• Hard — cannot be exceeded; writes get EDQUOT.
• Grace — time the soft limit can stay violated before it becomes hard.

sudo edquota -t                # edit grace periods

Step 3 — Apply the same defaults to new users§

edquota -p copies one user’s settings to others:

sudo edquota -p alice -u bob carol dave
# or every user above UID 1000:
sudo edquota -p alice $(awk -F: '$3 >= 1000 {print $1}' /etc/passwd)

A common pattern: set up a template user, then in scripts that create accounts call edquota -p template <newuser>.

Step 4 — Reports§

sudo repquota -a > /opt/course/42/quota-report
sudo repquota /home               # one filesystem
sudo repquota -ug /home           # users + groups
quota -u alice                    # what alice is using
quota -g devs

XFS-specific tools§

sudo xfs_quota -x -c 'limit bsoft=500m bhard=1g alice' /home
sudo xfs_quota -x -c 'report -h'  /home
sudo xfs_quota -x -c 'state'      /home

XFS adds project quotas (per-directory) — enabled via /etc/projects and /etc/projid:

echo "10:/data/site1" | sudo tee -a /etc/projects
echo "site1:10"        | sudo tee -a /etc/projid

sudo xfs_quota -x -c 'project -s site1' /data
sudo xfs_quota -x -c 'limit -p bsoft=5g bhard=6g site1' /data

Mailing users automatically when over quota§

sudo warnquota                    # send mail to over-quota users
sudo warnquota -g                 # also groups
# crontab once a day:
echo '0 6 * * * root /usr/sbin/warnquota' | sudo tee /etc/cron.d/warnquota

Mail templates: /etc/warnquota.conf.