quotaon Command Linux: Enable and Manage Disk Quotas Effectively

The quotaon command is a powerful Linux utility that enables disk quota enforcement on file systems. It allows system administrators to control and monitor disk space usage by users and groups, preventing any single user from consuming excessive storage resources that could impact system performance or availability.

What is the quotaon Command?

The quotaon command activates disk quota checking and enforcement on specified file systems. When quotas are enabled, the kernel tracks disk usage for each user and group, enforcing the limits defined in quota files. This is essential for multi-user environments where resource management is critical.

Basic Syntax and Options

The basic syntax of the quotaon command is:

quotaon [options] filesystem
quotaon [options] -a

Common Options

Prerequisites for Using quotaon

Before using the quotaon command, several prerequisites must be met:

1. Quota Support in Kernel

Verify quota support is compiled into your kernel:

cat /proc/filesystems | grep quota

2. Quota Tools Installation

Install quota tools on your system:

# Ubuntu/Debian
sudo apt-get install quota

# CentOS/RHEL/Fedora
sudo yum install quota
# or for newer versions
sudo dnf install quota

3. File System Configuration

The file system must be mounted with quota options. Edit /etc/fstab:

# Example fstab entry
/dev/sda2 /home ext4 defaults,usrquota,grpquota 0 2

Setting Up Disk Quotas

Step 1: Remount File System

After modifying fstab, remount the file system:

sudo mount -o remount /home

Step 2: Create Quota Files

Generate quota files for the file system:

sudo quotacheck -cum /home

This creates:

• aquota.user – User quota file
• aquota.group – Group quota file

Step 3: Enable Quotas

Now activate quotas using quotaon:

sudo quotaon /home

Practical Examples

Example 1: Enable User Quotas on Specific File System

sudo quotaon -u /home

Output:

quotaon: /home: quotas turned on

Example 2: Enable Group Quotas

sudo quotaon -g /home

Output:

quotaon: /home: group quotas turned on

Example 3: Enable All Quotas System-wide

sudo quotaon -a

Output:

/dev/sda2 [/home]: group quotas turned on
/dev/sda2 [/home]: user quotas turned on

Example 4: Verbose Output

sudo quotaon -v /home

Output:

/dev/sda2 [/home]: user quotas turned on
/dev/sda2 [/home]: group quotas turned on

Example 5: Check Quota Status

sudo quotaon -p /home

Output:

user quota on /home (/dev/sda2) is on
group quota on /home (/dev/sda2) is on

Setting User and Group Limits

After enabling quotas, set limits using the edquota command:

Setting User Limits

sudo edquota -u username

This opens an editor where you can set:

• Soft limit – Warning threshold
• Hard limit – Maximum allowed usage
• Grace period – Time before soft limit becomes hard limit

Setting Group Limits

sudo edquota -g groupname

Monitoring Quota Usage

Check User Quota Usage

quota -u username

Sample Output:

Disk quotas for user john (uid 1001):
Filesystem  blocks   quota   limit   grace   files   quota   limit   grace
/dev/sda2      156    5000   10000              28     100     200

System-wide Quota Report

sudo repquota /home

Sample Output:

*** Report for user quotas on device /dev/sda2
Block grace time: 7days; Inode grace time: 7days
                        Block limits                File limits
User            used    soft    hard  grace    used  soft  hard  grace
----------------------------------------------------------------------
root      --       0       0       0              3     0     0       
john      --     156    5000   10000             28   100   200       
mary      --     892    3000    5000             45    80   120

Advanced quotaon Usage

Force Enable Quotas

Sometimes you may need to force quota enabling:

sudo quotaon -f /home

Enable Quotas for Multiple File Systems

sudo quotaon /home /var /tmp

Troubleshooting Common Issues

Issue 1: “quotaon: cannot find //aquota.user”

Solution: Run quotacheck to create quota files:

sudo quotacheck -cug /home

Issue 2: “quotaon: using //quota.user on //dev/sda2: No such file or directory”

Solution: Ensure the file system is mounted with quota options and quota files exist.

Issue 3: Permission Denied

Solution: Ensure you have root privileges:

sudo quotaon /home

Best Practices

1. Regular Monitoring

Set up automated scripts to monitor quota usage:

#!/bin/bash
# Check quota usage daily
repquota -a | mail -s "Daily Quota Report" [email protected]

2. Grace Period Configuration

Set appropriate grace periods:

sudo edquota -t

3. Backup Quota Files

Regularly backup quota databases:

sudo cp /home/aquota.user /backup/

Integration with System Services

Automatic Quota Enabling at Boot

Create a systemd service to enable quotas at startup:

# /etc/systemd/system/quota.service
[Unit]
Description=Enable disk quotas
After=local-fs.target

[Service]
Type=oneshot
ExecStart=/usr/sbin/quotaon -a
RemainAfterExit=yes

[Install]
WantedBy=multi-user.target

Enable the service:

sudo systemctl enable quota.service

Security Considerations

• File Permissions: Quota files should be readable only by root
• Regular Audits: Monitor quota violations and adjust limits accordingly
• Backup Strategy: Include quota files in system backups

Related Commands

• quotaoff – Disable disk quotas
• quotacheck – Check and repair quota files
• edquota – Edit user/group quotas
• repquota – Display quota usage report
• quota – Display user quota information

Conclusion

The quotaon command is an essential tool for Linux system administrators managing multi-user environments. By properly implementing disk quotas, you can prevent resource abuse, ensure fair usage, and maintain system stability. Regular monitoring and appropriate limit setting are key to effective quota management.

Remember to always test quota implementations in a non-production environment first, and maintain regular backups of your quota configuration files. With proper setup and monitoring, disk quotas become a powerful tool for system resource management.