Last modified: March 08, 2022
This article is written in: 🇺🇸
Managing and monitoring disk usage is necessary for server maintenance, allowing administrators to identify disk space shortages caused by large log files, such as Apache or system logs, and malfunctioning applications that generate excessive data. Tools like df
provide quick overviews of available disk space, while du
helps analyze directory sizes to locate space hogs. For planning future storage needs, tracking data growth with monitoring software like Nagios or Grafana enables accurate forecasting and timely upgrades of storage hardware or cloud solutions. Regularly cleaning up unused files involves deleting obsolete backups, removing temporary files from /tmp
, archiving old user data, and eliminating redundant application caches using automated scripts or cleanup utilities like BleachBit.
TODO:
The df
(disk filesystem) command provides information about the filesystems on your machine. It shows details such as total size, used space, available space, and the percentage of space used. To display these statistics in a human-readable format, using units like KB, MB, or GB, you can use the -h
(human-readable) option.
For example, executing df -h
might produce an output like the following:
Filesystem | Size | Used | Available | Use% | Mounted on |
/dev/sda1 | 2.0T | 1.0T | 1.0T | 50% | / |
/dev/sda2 | 500G | 200G | 300G | 40% | /boot |
This output provides the following information:
Filesystem
: The name of each filesystem.Size
: The total size of each filesystem.Used
: The amount of space that has been used within each filesystem.Available
: The remaining free space within each filesystem.Use%
: The percentage of total space that has been used in each filesystem.Mounted on
: The mount point of each filesystem, indicating where it is accessible within the system's directory structure.du
CommandThe du
(disk usage) command is used to estimate the space occupied by files or directories. To display the output in a human-readable format, you can use the -h
option. The -s
option provides a summarized result for directories. For example, running du -sh .
will show the total size of the current directory in a human-readable format.
To find the top 10 largest directories starting from the root directory (/
), you can use the following command:
du -x / | sort -nr | head -10
An example output might look like this:
10485760 /usr
5120000 /var
2097152 /lib
1024000 /opt
524288 /boot
256000 /home
128000 /bin
64000 /sbin
32000 /etc
16000 /tmp
In this command:
du -x /
calculates the size of each directory within the root filesystem.sort -nr
sorts these sizes in descending numerical order.head -10
limits the output to the top 10 largest directories.This command sequence helps you quickly identify the directories consuming the most space on your system.
To further improve the speed of the du
command, especially when dealing with many subdirectories, you can use xargs -P
to parallelize the processing. This approach takes advantage of multiple CPU cores, allowing du
to run on multiple directories simultaneously. Additionally, combining it with awk
can help format the output more cleanly.
Here’s an enhanced example that finds the top 10 largest directories and uses xargs
to speed up the process:
find / -maxdepth 1 -type d | xargs -I{} -P 4 du -sh {} 2>/dev/null | sort -hr | head -10 | awk '{printf "%-10s %s\n", $1, $2}'
Explanation:
I. find / -maxdepth 1 -type d
: This command finds all directories at the root level (/
), limiting the search to the top-level directories only (-maxdepth 1
).
II. xargs -I{} -P 4 du -sh {} 2>/dev/null
:
xargs
takes the output of find
and passes each directory to the du
command.-I{}
is used to specify the replacement string {}
for the directory name.-P 4
specifies that up to 4 du
processes can run in parallel, leveraging multiple cores for faster execution.du -sh {}
calculates the size of each directory in a human-readable format.2>/dev/null
suppresses any error messages, such as permission denied errors.III. sort -hr
: Sorts the output in human-readable format and in reverse order, so the largest directories come first.
IV. head -10
: Limits the output to the top 10 largest directories.
V. awk '{printf "%-10s %s\n", $1, $2}'
: Formats the output, ensuring the size and directory name align neatly. The %-10s
ensures the size column has a fixed width, making the output more readable.
By using xargs -P
, you can significantly reduce the time it takes to compute the disk usage of directories, especially on systems with many directories and multiple CPU cores. This method effectively utilizes system resources to perform the operation more efficiently.
ncdu
CommandFor a more visual and interactive representation of disk usage, you can use ncdu
(NCurses Disk Usage). ncdu
is a ncurses-based tool that provides a user-friendly interface to quickly assess which directories are consuming the most disk space. If it is not already installed, you can install it via your package manager, such as apt
for Debian-based systems or yum
for Red Hat-based systems.
Running the command ncdu -x /
will start the program at the root directory (/
) and present an interactive interface. Here, you can navigate through directories using arrow keys and view their sizes, making it easier to identify space hogs.
Here’s an example of what the output might look like in a non-interactive, textual representation:
ncdu 1.15 ~ Use the arrow keys to navigate, press ? for help
--- / -----------------------------------------------------------------------
4.6 GiB [##########] /usr
2.1 GiB [#### ] /var
600.0 MiB [# ] /lib
500.0 MiB [# ] /opt
400.0 MiB [ ] /boot
300.0 MiB [ ] /sbin
200.0 MiB [ ] /bin
100.0 MiB [ ] /etc
50.0 MiB [ ] /tmp
20.0 MiB [ ] /home
10.0 MiB [ ] /root
5.0 MiB [ ] /run
1.0 MiB [ ] /srv
0.5 MiB [ ] /dev
0.1 MiB [ ] /mnt
0.0 MiB [ ] /proc
0.0 MiB [ ] /sys
Total disk usage: 8.8 GiB Apparent size: 8.8 GiB Items: 123456
In this output:
[##########]
visually represents the proportion of disk space used by each directory.ncdu
is especially useful for quickly finding large directories and files, thanks to its intuitive interface. The ability to easily navigate through directories makes it a powerful tool for managing disk space on your system.
Once you've identified what's using your disk space, the next step is often to free up space. Here are a few strategies:
apt-get autoremove
command can help clean out these unused packages.apt
, you can use the apt clean
command to clear the cache.find
command can be utilized to search for files exceeding a certain size, enabling users to review and decide if those files should be deleted. For example, find / -type f -size +100M
will list files larger than 100 MB.bleachbit
can efficiently remove temporary files, cache, cookies, internet history, and log files, helping to free up space.tar
, gzip
, or bzip2
, reducing their size and freeing up more disk space.For ongoing disk usage monitoring, consider setting up automated tasks. For instance, you can schedule a cron job that runs df
and du
at regular intervals and sends reports via email or logs them for later review.
Monitoring disk usage proactively can prevent potential issues related to low disk space, such as application errors, slow performance, or system crashes.
#!/bin/bash
# Script to monitor disk usage and report
# Set the path for the log file
LOG_FILE="/var/log/disk_usage_report.log"
# Get disk usage with df
echo "Disk Usage Report - $(date)" >> "$LOG_FILE"
echo "---------------------------------" >> "$LOG_FILE"
df -h >> "$LOG_FILE"
# Get top 10 directories consuming space
echo "" >> "$LOG_FILE"
echo "Top 10 Directories by Size:" >> "$LOG_FILE"
du -x / | sort -nr | head -10 >> "$LOG_FILE"
# Optionally, you can send this log via email instead of writing to a file
# For email, you can use: mail -s "Disk Usage Report" recipient@example.com < "$LOG_FILE"
# End of script
disk_usage_monitor.sh
./etc/cron.daily
. This directory is used for scripts that should be run daily by the system's cron daemon. Here's how you can do it:
sudo chmod +x /path/to/disk_usage_monitor.sh && sudo mv /path/to/disk_usage_monitor.sh /etc/cron.daily/
/
). Discuss why monitoring free space on the root is crucial for system stability./var
, /home
, or /boot
./home
directory for each user. Discuss the significance of managing space within /home
and how it affects individual user accounts..txt
, .jpg
, .log
). Explain how file type classification can help in identifying disk space hogs and in organizing cleanup strategies.