How to Quickly Identify Disk Space Hogs on Linux Servers

During server operations, disk space alerts are common. First, run

df -Hl

to view current usage and verify the alert.

How to Find Large Directories or Files Consuming Disk Space?

A simple way is to start at the root directory and execute

du -hs

to list the size of each top‑level directory, then drill down into the larger ones.

A more efficient method uses

du

with the

-d

or

--max-depth

option to limit the depth of the search, and pipes the output to

grep

to filter for entries measured in G or T, then sorts the results.

Alternatively, the

find

command can locate large files directly:

<code>find / -type f -size +1G -exec du -h {} \;</code>

In terms of performance,

find

is generally faster and more flexible than

du

for this purpose.

These techniques help you quickly pinpoint the directories or files that are hogging disk space.

Why Is Disk Space Mysteriously Consumed?

Sometimes the total size reported by

du

does not match the usage shown by

df

. For example,

df

may indicate 37 GB used, while summing

du -hs

across the filesystem yields only about 10 GB. This discrepancy often means that deleted files are still holding space because they remain open by a process.

You can reveal such orphaned files with

lsof +L1

:

<code>lsof +L1</code>

The output may show a large log file (e.g., ~28 GB) that has been deleted but not released. Restarting the associated service (e.g., Tomcat) frees the space.

Another common confusion arises when the sum of

Used

and

Avail

is less than

Size

. Linux reserves a percentage of disk space (default 5 %) for the root user as a safety buffer, ensuring critical applications have room even when the disk appears full.

You can adjust this reserved space with

tune2fs -m 1 /dev/vda1

to set the reservation to 1 %.

After reducing the reserved percentage, the previously “missing” space becomes available.