Troubleshooting Disk Space Not Released After Deleting Files on Linux

One business system's server monitoring alert indicated that disk usage had reached 50%; after manually deleting large log files, the space seemed partially freed, but a subsequent alert revealed that the space was not fully released.

Problem reproduction and solution:

1. Disk space usage shows 504 GB total, with 298 GB actually used.

Linux deletion strategy: Linux has no recycle bin, so deleted files are moved to the /tmp directory and periodically cleared.

Many servers are installed without a separate /tmp partition, so /tmp can consume a large amount of space; clearing /tmp can immediately free space.

2. Solution approach

Normally, deleted files free space, but exceptions occur when a file is locked by a process or continuously written to; understanding this requires knowledge of Linux file storage mechanisms.

A file consists of data and pointer parts; the pointer resides in the file system's metadata. Deleting data removes the pointer from metadata, allowing the space to be overwritten. If a process locks the file, the pointer remains, so the kernel treats the file as still existing, and df shows the space as used.

3. Problem investigation

To check if a process is still holding the deleted file, use the Linux lsof command to list open deleted files:

lsof | grep delete

Identify large files, kill the associated process with kill -9 <pid> , and the space will be released.

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