Ubuntu Disk Space Guide: How to Check Free Space and Fix It—All You Need

1. Prerequisite Knowledge: Storage Structure and Mounting in Linux/Ubuntu

When checking storage capacity on Ubuntu (and most Linux‑based OSes), there are some fundamental structures you need to understand correctly. This section organizes the concepts that often cause confusion:

• Device and partition meanings
• Mounting and mount points
• Basics of LVM (Logical Volume Management)
• Typical Ubuntu configurations

We’ll walk through each point step by step.

1.1 Devices and Partitions Basics

Devices (Physical & Logical Disks)

In Linux, each storage device is treated as a device file. For example, HDDs, SSDs, USB drives, etc., appear as /dev/sda, /dev/sdb, /dev/nvme0n1, and so on.
The trailing letter (a, b, c…) indicates the order in which the system detected the devices.

Partitions

A single physical device can be used as‑is, but it’s common to split it into several logical sections (partitions). Partitioning lets you separate the OS, data, logs, etc., for easier management.

For example, /dev/sda1, /dev/sda2 denote the first and second partitions on device sda. A filesystem is created on each partition, and the actual data is stored there.
(Example explanation of partitions in Linux) Engineer’s Entrance

Partitions use a partition‑table format such as MBR (old) or GPT (new), each with its own constraints and advantages.

1.2 Mounting and Mount Points

Mount

To make a filesystem usable, you must mount it—i.e., associate a partition (or logical volume) with a specific directory (the mount point). Without mounting, you cannot access the data on that partition.

For instance, even if /dev/sda1 contains an ext4 filesystem, you must run mount /dev/sda1 /mnt/data before you can work under /mnt/data.

Mount Point

The directory where you mount a filesystem is called a mount point. Typical examples:

• / – root, the starting point of the whole system
• /home – user home directories
• /var – logs, caches, variable data
• /boot – boot‑related files

Assigning different partitions to different mount points is a common practice.

In Ubuntu and most Linux OSes, the file /etc/fstab lists “which device/UUID is mounted where (automatically at boot).”

1.3 Overview of LVM (Logical Volume Management)

Pure partitioning can make later changes difficult. LVM (Logical Volume Manager) solves this.

Core LVM Components

• Physical Volume (PV) – a physical disk or partition.
• Volume Group (VG) – aggregates multiple PVs into a single large pool.
• Logical Volume (LV) – a slice taken from a VG; a filesystem is created on an LV.

This hierarchy lets you expand or shrink logical volumes later, or add more physical disks to the pool.

Benefits & Caveats of LVM

Benefits

• Flexible resizing
• Combine multiple disks into one pool
• Easy to create snapshots for backup

Caveats

• More complex to configure and operate
• Risk of data loss if mishandled
• Expansion steps differ from non‑LVM setups

Ubuntu’s installer often offers an LVM option, but many users choose not to use it depending on their needs.

1.4 Typical Ubuntu Configurations

The exact layout varies, but common patterns include:

Single‑Partition (Simple) Layout

All files live under the root (/). Simpler, but later splitting or expanding can be hard.

Split Layout Example

• / – system files
• /home – user data
• /var – logs and variable data
• /boot – boot loader files
• Swap (swap partition or swap file)

Separating these helps prevent log or cache growth from filling the whole system.

LVM + Logical Volumes

A more advanced setup:

• Physical disks → PVs
• Multiple PVs → VG
• /, /home, /var, etc. → separate LVs
• Add or expand LVs later as needed

With LVM you can add disks or enlarge logical volumes flexibly.

2. Basic Commands to Check Capacity

On Ubuntu, using the command line is the most reliable and flexible way to check disk usage. Even on headless servers, you can see exactly which disks are used and which directories consume space.

Below are the core df and du commands, plus a few helper tools.

2.1 Checking Whole Filesystems with df

What df Does

df (disk free) displays total, used, and available space for each filesystem. It’s the most common way to check capacity on Linux.

Basic Usage

df -h

The command lists every filesystem in “human‑readable” units (K, M, G). Main columns:

Example

$ df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2       100G   55G   40G  59% /
/dev/sda1       512M  120M  392M  24% /boot
tmpfs            16G   32M   16G   1% /run

From this output you can see at a glance how much space each area is using.

Notes

• Unmounted partitions are not included in df‘s output.
• If Snap packages (/var/lib/snapd/snaps) are consuming space, you’ll need to check them separately.
• Some mount points are invisible without root privileges.

2.2 Checking directory‑level usage with the du command

Overview of du

du (disk usage) is a command that reports the size of directories and files.
While df gives you the “big picture,” du helps you find out “where the heavy stuff is.”

Basic usage

du -sh /home

In this example, the total usage of the /home directory is shown in a “human‑readable format” (-h).

Common options

Example (overall comparison)

sudo du -h --max-depth=1 /var

Sample output:

1.2G    /var/log
2.5G    /var/lib
800M    /var/cache
4.5G    /var

This lets you quickly see which folders are taking up space.

Advanced: Sort by size

By combining du with sort, you can easily pinpoint large directories.

sudo du -hsx /* | sort -rh | head -10

This command calculates the usage of each top‑level folder and displays the top 10.
It’s very effective for hunting down the “space‑eating culprits” across the system.

Notes

• Deep directory trees can take a while to process.
• Without root privileges, some directories won’t report accurate sizes.
• Even on fast SSDs, measuring tens of gigabytes can take several minutes.

2.3 Other handy helper commands & tools

lsblk: View block device layout

lsblk

lsblk displays disk devices and their partition layout in a tree format.
It’s a convenient way to visually correlate sizes with mount points.

Example:

NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINTS
sda      8:0    0   100G  0 disk
├─sda1   8:1    0   512M  0 part /boot
└─sda2   8:2    0  99.5G  0 part /

ncdu: Interactive disk‑usage analyzer

If you want a more intuitive interface than du, try ncdu (NCurses Disk Usage).
Install it with:

sudo apt install ncdu

Run it:

sudo ncdu /

Use the arrow keys to expand and collapse folders and see which directories are consuming space.
Because it works without a GUI, it’s popular on servers as well as workstations.

Combining with find

To locate only the largest files, use find:

sudo find / -type f -size +1G

This searches for all files larger than 1 GB, helping you identify unnecessary large files such as logs or virtual machine images.

2.4 Which method to use? (Comparison summary)

3. Checking disk usage with a GUI (Ubuntu Desktop)

Ubuntu provides graphical tools that let you see disk usage without opening a terminal. Below are two common methods.

• The built‑in File Manager (Nautilus)
• The Disk Usage Analyzer (Baobab)

We’ll look at the features and how to use each.

3.1 Checking free space with the File Manager (Nautilus)

The default Ubuntu method

If you’re using Ubuntu Desktop, the simplest way to see disk space is to open the File Manager (Nautilus).

1. Click the Files icon in the left dock (application launcher).
2. Look at the status bar at the top‑right or bottom‑left of the window.
3. You’ll see something like “xx GB of yy GB used” or “zz GB free.”

This gives you an immediate view of the system drive’s free space.

Viewing details via Properties

Right‑click a folder or drive icon and choose Properties.
The dialog shows the used and free space for that specific folder, which is handy for checking directories such as /home or /Downloads.

Pros and cons

The GUI is great for a quick “feel” of overall usage, but for deeper analysis you’ll want Baobab.

3.2 Disk Usage Analyzer (Baobab)

What is Baobab?

Baobab (Disk Usage Analyzer) is a graphical utility that scans your file system and presents the results as an interactive treemap or ring chart. It lets you quickly spot large directories and files with a visual overview.

Installation

sudo apt install baobab

Launching

You can start it from the application menu (search for “Disk Usage Analyzer”) or run:

baobab

How to use

1. Choose a location to scan (e.g., “Home Folder,” “Filesystem,” or a custom path).
2. After the scan finishes, the treemap displays each folder as a rectangle sized proportionally to its space consumption.
3. Hover or click a rectangle to see the exact size and path.
4. Right‑click a folder to open it in the file manager or delete it directly.

Because Baobab works without needing a full desktop environment, it’s also useful on lightweight Ubuntu flavors.

Benefits

• Visual, intuitive representation of disk usage.
• Easy navigation to the biggest space consumers.
• No need to remember command‑line options.

Limitations

• Scanning very large filesystems can take a few minutes.
• Requires a graphical session (not suitable for headless servers).

Baobab (official name: Disk Usage Analyzer) is a graphical tool available by default on Ubuntu that visually shows how much space each folder is using with pie charts and treemaps.

It is installed on most systems by default, but if it isn’t present you can add it with:

sudo apt install baobab

Baobab - Community Help Wiki

…

How to Launch

1. Search “Disk Usage” in Activities (top‑left search bar)
2. Click Disk Usage Analyzer (Baobab) to start it
3. After launch, choose Scan Folder or Scan Whole Filesystem

After a short scan, a pie chart or tree view will display each directory’s usage visually.

Example View (Image)

• The farther out you go, the deeper the directory hierarchy
• Each segment’s size is represented by the area of the pie slice

The visual cue makes it easy to see which folders are bloated at a glance.

Main Features

Benefits and Caveats

Benefits

• Graphical display makes it intuitive for beginners
• Helps decide what to delete or reorganize
• Running as root lets you analyze system partitions as well

Caveats

• Scanning the entire system can take time
• Permission restrictions may prevent accurate measurement of some folders
• Large disks can increase memory usage while scanning

3.3 Checking Disk Information with GNOME Disks

Ubuntu also includes the standard app GNOME Disks (Disk Utility).
It lets you inspect the disk structure itself, showing more than just free space:

• Device name (e.g., /dev/sda)
• Filesystem type (ext4, NTFS, etc.)
• Mount point
• Usage graph

How to launch:

1. Search for “Disks” in Activities
2. Open GNOME Disks
3. Select a disk from the list on the left

A visual gauge shows usage, providing the same information as df in a graphical form.

3.4 When to Use GUI vs. Command Line

On an Ubuntu desktop, GUI tools are often enough for storage management.
However, for precise troubleshooting or server administration, command‑line tools like df and du are essential.

3.5 If No GUI Is Available (Server Users)

If you’re running Ubuntu Server or another environment without a GUI, Baobab and file managers aren’t usable.

In that case, rely on the df, du, and ncdu commands introduced earlier; they provide detailed, text‑based storage analysis.

Summary

Using a GUI lets you check storage and pinpoint cleanup points with just a few clicks.
Baobab, in particular, is a staple tool used by everyone from Ubuntu newcomers to power users.
By mixing the methods described in this chapter, everyday storage monitoring becomes much easier.

4. Investigation Steps and Remedies for Low Disk Space

Over time, long‑term use and cumulative package updates can cause disk space to run low on Ubuntu.
Leaving a system in a low‑space state can lead to failed updates, missing logs, and overall instability.
This section walks through how to diagnose low‑space issues and effective ways to resolve them step by step.

4.1 Recognizing Low‑Space Symptoms

First, identify signs that storage is running out. Look for:

• apt upgrade reporting “not enough free space”
• GUI warning “disk space is low”
• Applications failing to save settings or write logs
• /var or /tmp filling up, causing sluggish behavior

When you see these, it’s time to determine where the space is being used, not just to add more.

4.2 Step 1: Get an Overview of Usage (df)

Start with df -h to see overall capacity:

df -h

Sample output:

Filesystem      Size  Used Avail Use% Mounted on
/dev/sda2        50G   48G  1.2G  98% /
/dev/sda1       512M  120M  392M  24% /boot

Any mount point with Use% ≥ 90% needs attention, especially /, /var, or /home.

4.3 Step 2: Find Which Directories Consume Space (du)

Once you know the problematic partition, drill down with du.

Example: Show Top 10 Space‑Consuming Items

sudo du -hsx /* | sort -rh | head -10

Sample output:

15G /var
10G /home
5.2G /usr
3.1G /snap

A large /var usually points to logs or caches; a large /home indicates user data.

Dig Deeper Inside /var

sudo du -hsx /var/* | sort -rh | head -10

By traversing the hierarchy, you can pinpoint the exact directories that are hogging space.

4.4 Step 3: Remove Unnecessary Files and Caches

After identifying the culprits, start cleaning up safe-to‑delete items.

(1) Clean APT Cache

Ubuntu stores temporary package files in /var/cache/apt/archives. Deleting them can free several gigabytes.

sudo apt clean
sudo apt autoremove

• apt clean – removes all cached package files
• apt autoremove – removes packages that are no longer needed

(2) Delete Old Log Files

/var/log is a common source of bloat.

sudo journalctl --vacuum-time=7d

The above deletes system logs older than 7 days.
You can also manually delete unnecessary .gz (compressed log) files.

sudo rm -f /var/log/*.gz

(3) Remove old Snap package versions

On Ubuntu, old versions of Snap apps are kept automatically.
You can delete old snaps with the following command.

sudo snap list --all | grep disabled | awk '{print $1, $3}' | 
while read snapname revision; do
  sudo snap remove "$snapname" --revision="$revision"
done

Alternatively, you can use a simple “Snap Cleaner” type utility.

(4) Delete thumbnail cache

If you work with many images or videos, a large amount of cache accumulates in ~/.cache/thumbnails.

rm -rf ~/.cache/thumbnails/*

(5) Empty the trash

Files deleted via the GUI may still reside in ~/.local/share/Trash/files.

rm -rf ~/.local/share/Trash/*

4.5 Step 4: Mitigating Bloat from Applications and Logs

(1) When using Docker

When using Docker, unnecessary images and containers can consume space.

docker system df
docker system prune -a

• docker system df: Check Docker‑related usage
• docker system prune -a: Remove unused images and containers

(2) When heavily using Flatpak or Snap

In environments with many GUI apps installed, leftover app artifacts (old versions) tend to accumulate.
Clean up with commands like flatpak uninstall --unused.

(3) Review log rotation settings

Check /etc/logrotate.conf and /etc/logrotate.d/, and set appropriate retention periods and size limits to help prevent recurrence.

4.6 Step 5: Fundamentally Resolve by Resizing or Adding Disks

If deleting files alone isn’t enough, consider the following configuration changes.

(1) When using LVM

In environments with LVM (Logical Volume Manager), logical volumes can be easily expanded.

sudo lvextend -L +20G /dev/ubuntu-vg/ubuntu-lv
sudo resize2fs /dev/ubuntu-vg/ubuntu-lv

This allows you to increase the capacity of /.

(2) Add a new disk and mount it

Mount new storage at /mnt/data (or similar), and move large directories (e.g., /var/lib/docker or /home) there.

(3) Leverage cloud storage

Moving logs and backups to Google Drive, Dropbox, Nextcloud, etc., is another option.

4.7 Regular Checks to Prevent Recurrence

Running out of space is a problem that can be avoided by regular monitoring.
Adopting the following practices is effective.

• Regularly check df -h and du -sh /var
• Create a script to automatically check large directories
• Set up email notifications when usage exceeds thresholds (cron + mailutils, etc.)

Simple example:

#!/bin/bash
THRESHOLD=90
USAGE=$(df / | awk 'NR==2 {print $5}' | sed 's/%//')
if [ "$USAGE" -gt "$THRESHOLD" ]; then
  echo "Disk usage on / has exceeded ${THRESHOLD}%!" | mail -s "Disk Alert" admin@example.com
fi

4.8 Summary: Prioritizing Space‑Saving Measures

When Ubuntu runs low on space,
Identify the heavy hitters → Delete from safe areas → Review the configuration
Following these three steps solves most issues.

5. Advanced Tips (Useful Tricks & Caveats)

Even after using the methods above to check and clean space, the disk can fill up again over time.
Here are some advanced techniques to keep Ubuntu running smoothly.

5.1 Automate Regular Disk Checks

Running df or du manually is tedious, but automation scripts can reduce the effort.
Register a simple monitoring script in cron to send alerts when usage exceeds a threshold.

Example: Script that emails when free space drops below 10%

#!/bin/bash
THRESHOLD=90
USAGE=$(df / | awk 'NR==2 {print $5}' | sed 's/%//')
if [ "$USAGE" -gt "$THRESHOLD" ]; then
  echo "Warning: Root disk usage has reached ${USAGE}%." |
  mail -s "Ubuntu Disk Warning" user@example.com
fi

Save this as /usr/local/bin/check_disk.sh and make it executable with chmod +x.
Then register it in crontab -e like this:

0 8 * * * /usr/local/bin/check_disk.sh

→ The check runs automatically every morning at 8 AM.

Handy Points

• Notifications can also be sent via Slack Webhook, LINE Notify, etc.
• Can be extended to monitor multiple mount points simultaneously

5.2 One‑liner to Find Large Files

Often, a shortage is caused by a few huge files.
The following one‑liner lists files larger than 1 GB.

sudo find / -type f -size +1G -exec ls -lh {} ; | awk '{print $9 ": " $5}'

/var/log/syslog.1: 1.5G
/var/lib/docker/overlay2/.../diff/usr/lib/libchrome.so: 2.3G
/home/user/Downloads/video.mp4: 4.1G

In this way, you can quickly find files that should be deleted or moved.

Example: Search only specific directories

sudo find /var -type f -size +500M

→ Useful for finding files larger than 500 MB under /var.

5.3 Alias frequently used commands

Typing long commands every time is tedious, so setting up aliases is efficient.

Example: Append to ~/.bashrc

alias dfh='df -h --total'
alias duh='sudo du -hsx /* | sort -rh | head -10'
alias logs='sudo du -hs /var/log/* | sort -rh | head -10'

Apply after setting:

source ~/.bashrc

Now,

• dfh → Check total capacity
• duh → View top 10 folders
• logs → Investigate log sizes

You can execute such operations instantly.

5.4 Continuously monitor disk usage changes (monitoring)

When running Ubuntu long‑term, you may encounter the issue of “disk space silently increasing.”
Therefore, recording disk usage changes as a history is useful.

Example: Script to log disk usage to a file

#!/bin/bash
df -h / | awk 'NR==2 {print strftime("%Y-%m-%d %H:%M:%S"), $3, $4, $5}' >> /var/log/disk_usage.log

Running this once daily via cron lets you track disk usage trends later.

More advanced methods

• Install collectd or netdata for graphing
• Use Prometheus + Grafana for monitoring visualization
• When on cloud, integrate with AWS CloudWatch or GCP Ops Agent

You can monitor at the operational management level without relying on GUI tools.

5.5 Beware of permission barriers

When checking or deleting disk usage, you may not get accurate results without root privileges.

Example:

du -sh /var

Even if you run this, a regular user will have some folders skipped with “Permission denied,” resulting in a lower value than the actual usage.

→ As a countermeasure, prepend sudo or operate with administrative rights.

5.6 Considerations for SSD/HDD environments

SSD environments

• To avoid unnecessary writes, run TRIM regularly with fstrim:
  sudo systemctl enable fstrim.timer
  This allows the SSD to optimize deleted blocks.

HDD environments

• Logs and caches tend to fragment, so rebooting after deleting unnecessary files can be effective.
• Running I/O‑heavy du commands is best done during low‑load periods, such as late at night.

5.7 Systematize capacity management to prevent recurrence

Finally, the optimal solution for capacity management is habitual and systematic.

Practical checklist

• Regularly check df -h
• Check /var/log growth monthly
• Run apt autoremove weekly
• Periodically delete unnecessary Snap and Docker data
• Have an automated notification script in place

If you perform these regularly, most disk space issues can be prevented.

Summary

This section introduced advanced techniques to make Ubuntu disk space management more efficient.
The key points are three:

1. Early detection through automation and notifications
2. Operational efficiency via aliases and one‑liners
3. Safe management by considering permissions and device characteristics

Combining these transforms capacity management from a tedious task into an integral part of system operations.

6. FAQ (Frequently Asked Questions)

Q1. What is a simple way to check current free space on Ubuntu?

The easiest way is to run the following command in a terminal.

df -h

This command shows each drive (partition)’s total size, used space, and free space at a glance.
Adding the -h option displays the sizes in a human‑readable format (GB, MB).

Q2. How can I check disk usage per directory?

Use the du command.
To check a specific folder’s usage, run:

du -sh /home

Option meanings:

• -s: display only the total
• -h: show sizes in human‑readable units

For more detailed per‑folder usage, use:

sudo du -h --max-depth=1 /var

Q3. What’s the difference between df and du?

In short, they measure different things.

For example, use df to see overall free space on /, and use du to see how much a specific folder consumes.

Q4. How can I check free space via the GUI?

On Ubuntu Desktop, you can visually check using the File Manager (Nautilus) or Disk Usage Analyzer (Baobab).

• File Manager → Bottom bar shows “Remaining XX GB”
• Baobab → Graphical breakdown of usage

Both are beginner‑friendly and show results with just a click.

Q5. If I get a “disk full” warning, what should I delete first?

Start by removing safe caches and unnecessary files.
The recommended order is:

1. Clear APT cache sudo apt clean
2. Remove unnecessary packages sudo apt autoremove
3. Clean up logs sudo journalctl --vacuum-time=7d
4. Empty trash and thumbnail cache rm -rf ~/.cache/thumbnails/* && rm -rf ~/.local/share/Trash/*

These steps alone can free several gigabytes.

Q6. I heard Snap apps can bloat disk space. What can I do?

Snap keeps each version of an app, so old revisions may linger.
You can delete unnecessary old revisions with the following command:

sudo snap list --all | grep disabled | awk '{print $1, $3}' | 
while read snapname revision; do
  sudo snap remove "$snapname" --revision="$revision"
done

Alternatively, you can manually remove it using the GUI tool Snap Store.

Q7. What should I do when /var or /home is too large?

• /var – clean up logs (/var/log) and caches (/var/cache)
• /home – back up or move downloads and video files to external storage

If you need to increase capacity, you can expand the volume with LVM or mount a new disk and manage the space separately.

Q8. Running du takes a long time. Is there a way to speed it up?

du scans every file recursively, so it can be slow on directories with many items.
The following tricks can help:

• Use --max-depth=1 to skip deep sub‑directories
• Exclude unnecessary folders (e.g., --exclude=/proc)
• Use the ncdu command (interactive view)

sudo apt install ncdu
sudo ncdu /

ncdu feels lightweight and provides a visual way to inspect disk usage.

Q9. How can I prevent running out of space again?

Regular maintenance helps a lot:

• Run sudo apt autoremove once a week
• Check /var/log and /home usage monthly
• Save the output of df -h to a log and track changes
• Periodically delete old Snap or Docker data
• On SSDs, enable automatic trimming with sudo systemctl enable fstrim.timer

Automating these tasks can keep disk‑space problems at bay.

Q10. What are my options for expanding storage?

There are three common approaches:

1. Extend the LVM volume
   bash sudo lvextend -L +10G /dev/ubuntu-vg/ubuntu-lv sudo resize2fs /dev/ubuntu-vg/ubuntu-lv
2. Add a new disk and mount it – create a mount point such as /mnt/data and distribute the load.
3. Use cloud storage – move large files to Google Drive, Nextcloud, etc.

If adding physical storage isn’t feasible, archiving old files is also effective.

Q11. Can I check disk usage without root privileges?

Basic df -h works for any user, but du needs permission to read certain directories (e.g., /var/log).
In a non‑root environment, limit the scan to your home directory:

du -sh ~/*

Q12. How do I check storage on a headless (server) system?

Since the server edition of Ubuntu lacks a GUI, use these commands instead:

Combining them lets you analyze disk usage comfortably without a GUI.

Q13. Is there any risk of breaking the system while checking storage?

Simply checking usage carries no risk.
However, be careful when you start deleting or resizing:

• Double‑check paths before using sudo rm -rf
• Never delete system directories like /bin, /lib, or /etc
• If you’re unsure, back up first

Q14. Any hidden tricks to save space?

• Shorten log retention (/etc/logrotate.conf settings)
• Remove unnecessary language packs: sudo apt install localepurge
• Purge old kernels (they sometimes linger): sudo apt autoremove --purge

These steps can free anywhere from a few hundred MB to several GB.

Q15. Recommended tools for monitoring disk usage?

Ubuntu offers several useful monitoring tools:

Summary

The key takeaways for managing disk space on Ubuntu are:

1. Use df for overall view and du for detailed inspection
2. Delete unnecessary data in a safe order (APT → logs → caches)
3. Automate cleanup and monitoring to prevent recurrence

By making these practices routine, disk‑space issues become rare. Managing storage may seem mundane, but it’s one of the most critical maintenance tasks for a stable Ubuntu system.