How to check if disk quotas are enabled in Linux

Introduction

In this lab, you will learn how to determine if disk quotas are enabled and configured on a Linux system. You will explore three key methods: using the quota command to check current user and group quota status, examining the /etc/fstab file to verify filesystem mount options related to quotas, and utilizing the quotacheck command to inspect the quota setup on specific filesystems. By the end of this lab, you will be able to effectively check for the presence and configuration of disk quotas in a Linux environment.

Skills Graph

Check quota status with quota

In this step, you will learn how to check the disk quota status for users and groups using the quota command. Disk quotas are used to limit the amount of disk space or the number of files a user or group can consume on a filesystem.

First, let's check the quota status for the current user. Open your terminal if it's not already open. You can do this by clicking the Xfce Terminal icon on the left side of the desktop.

Now, type the following command and press Enter:

quota

If quotas are enabled and configured on the filesystem, you might see output similar to this:

Disk quotas for user labex (uid 5000):
     Filesystem  blocks   soft   hard  inodes   soft   hard
      /dev/sda1       0      0      0       0      0      0

Let's break down the output:

• Filesystem: The filesystem on which the quota is applied (e.g., /dev/sda1).
• blocks: The current disk space usage in blocks (usually 1KB blocks).
• soft: The soft limit for disk space. If usage exceeds this, a warning is issued.
• hard: The hard limit for disk space. Usage cannot exceed this.
• inodes: The current number of files used.
• soft: The soft limit for the number of files.
• hard: The hard limit for the number of files.

In this case, the output shows all zeros, indicating that no specific quotas are set for the labex user on /dev/sda1.

You can also check the quota status for a specific user by providing their username as an argument. For example, to check the quota for the root user, you would type:

quota root

The output would likely also show zeros if no quotas are set for the root user:

Disk quotas for user root (uid 0):
     Filesystem  blocks   soft   hard  inodes   soft   hard
      /dev/sda1       0      0      0       0      0      0

Similarly, you can check the quota status for a group using the -g option followed by the group name. For example, to check the quota for the labex group:

quota -g labex

Again, you would likely see output similar to this if no group quotas are set:

Disk quotas for group labex (gid 5000):
     Filesystem  blocks   soft   hard  inodes   soft   hard
      /dev/sda1       0      0      0       0      0      0

The quota command is a quick way to see the current usage and limits if quotas are active. In the next steps, we will explore how to verify if quotas are enabled on a filesystem.

Click Continue to proceed to the next step.

Verify quota in /etc/fstab

In the previous step, you used the quota command to check the current quota status. However, the quota command only shows information if quotas are already active on a filesystem. To determine if a filesystem is configured for quotas, you need to look at the /etc/fstab file.

The /etc/fstab file (filesystem table) is a configuration file that contains information about all the filesystems on your system. It tells the operating system how to mount filesystems at boot time. Quota options are often specified in this file.

We will use the cat command to view the contents of /etc/fstab. Since /etc/fstab is a system file, you might need sudo to access it, although cat usually works without it for reading.

Type the following command in your terminal and press Enter:

cat /etc/fstab

You will see output similar to this, which lists the filesystems and their mount options:

## /etc/fstab: static file system information.
#
## Use 'blkid' to print the universally unique identifier for a
## device; this may be used with UUID= as a more robust way to name devices
## that works even if disks are added or removed. See fstab(5).
#
## <file system> <mount point>   <type>  <options>       <dump>  <pass>
/dev/sda1       /               ext4    errors=remount-ro 0       1
/dev/sda2       none            swap    sw              0       0

Look for the line corresponding to the root filesystem (/), which is typically /dev/sda1 and mounted at /. In the <options> column for this line, you would look for options like usrquota or grpquota.

• usrquota: Indicates that user quotas are enabled for this filesystem.
• grpquota: Indicates that group quotas are enabled for this filesystem.

In the example output above, the options for /dev/sda1 are errors=remount-ro. This means that user and group quotas are not enabled by default in this configuration.

If quotas were enabled, the line might look something like this (this is just an example, do not expect to see this in your current environment):

/dev/sda1       /               ext4    errors=remount-ro,usrquota,grpquota 0       1

By examining /etc/fstab, you can verify if the filesystem is configured to support quotas when it is mounted.

Click Continue to move to the next step, where we will look at the quotacheck command.

Inspect quota setup with quotacheck

In this step, you will use the quotacheck command. The quotacheck command is used to scan a filesystem for disk usage and create, check, and repair quota files. It's a crucial step when setting up or verifying quotas.

Before running quotacheck, it's important to understand that it needs to scan the filesystem. For accurate results, the filesystem should ideally be unmounted or mounted read-only. However, in a live system, this is often not feasible for the root filesystem (/). quotacheck can often run on a mounted filesystem, but it might issue warnings.

Since we are working in a LabEx environment and cannot easily unmount the root filesystem, we will run quotacheck on the mounted filesystem.

The basic syntax for quotacheck is quotacheck [options] filesystem. We will use the following options:

• -c: Create new quota files (aquota.user and aquota.group).
• -u: Check user quotas.
• -g: Check group quotas.
• -v: Verbose output, showing what the command is doing.
• -M: Don't try to remount the filesystem read-only.

We need to run quotacheck with sudo because it requires root privileges to scan the filesystem and create/modify quota files.

Type the following command in your terminal and press Enter:

sudo quotacheck -cugvM /

You will see output indicating that quotacheck is scanning the filesystem. The exact output may vary depending on the system state, but it will look something like this:

quotacheck: Scanning /dev/sda1 [/] done
quotacheck: Checked 10 directories and 100 files

This command scans the root filesystem (/), checks for user (-u) and group (-g) disk usage, creates new quota files (-c) if they don't exist, provides verbose output (-v), and avoids trying to remount the filesystem read-only (-M).

After running quotacheck, if the filesystem is configured for quotas in /etc/fstab and the quota package is installed, it would typically create or update the quota files (aquota.user and aquota.group) at the root of the filesystem (e.g., /aquota.user, /aquota.group).

You can check for the existence of these files using the ls command:

ls -l /aquota.*

If quota files were created, you might see output like this (again, this depends on the system configuration and if quotas are truly active):

-rw------- 1 root root 6144 Feb 13 10:00 /aquota.group
-rw------- 1 root root 7168 Feb 13 10:00 /aquota.user

In our current LabEx environment, since quotas are not fully configured, these files might not be created or might show zero size. The key takeaway is understanding that quotacheck is the tool used to generate and maintain the data in these quota files based on the actual disk usage.

This step concludes our exploration of checking quota status and configuration files. You've learned how to use quota to see current usage, cat /etc/fstab to check for quota mount options, and quotacheck to scan the filesystem and manage quota data files.

Click Continue to finish the lab.

Summary

In this lab, you learned how to check if disk quotas are enabled in Linux. You started by using the quota command to view the disk quota status for users and groups, understanding the output fields like filesystem, blocks, soft and hard limits for both blocks and inodes. You practiced checking quotas for the current user and a specific user like root.

The lab also guided you on how to verify quota configuration by inspecting the /etc/fstab file to see if the usrquota or grpquota options are present for mounted filesystems. Finally, you learned to use the quotacheck command to scan filesystems for disk usage and update quota files, which is a crucial step in setting up or verifying quotas.