Azure App Service with [Linux-based Python 3.11]: OSError [Errno 28] No space left on device

Question

Azure App Service with [Linux-based Python 3.11]: OSError [Errno 28] No space left on device

Dcm 0

All of a sudden, my Azure App Service (Linux-based, Python 3.11) started throwing the following error:

OSError: [Errno 28] No space left on device

This occurred at the following code location:

with open(log_file_path, 'a', encoding="utf-8") as file:

    file.write(log_entry)
```Note: The file already exists.

File path: `/home/site/wwwroot/

Alekhya Vaddepally 585 Reputation points Microsoft External Staff

2025-04-23T12:47:56.2966667+00:00
Hi Dcm,

The Azure app service on Linux has limited temporary storage, usually up to 1 GB in /home directory, including /home /site /wwwroot. If it fills the place (from log, temp files, etc.), then the operation of any further writing such as logging will throw this error.

Remove any unnecessary or oversized log files /from home using Kudu (App Service Advanced Tools) or through the SSH session for the container.

If you are storing the log in the file system, consider installing log rotation or retention policies to avoid bloating the disc.

Instead of writing the logs directly on the file system, we recommend sending our logs to an azure monitor or application insights, which are designed to handle large versions of the log without using the local disk space.

Alternative - Extend temporarily available space: You can consider scaling your app service plan (eg, basic to standard or higher) that increases the available disk space as part of the scheme.
https://learn.microsoft.com/en-us/azure/azure-monitor/agents/azure-monitor-agent-troubleshoot-linux-vm-rsyslog#issues
if you have any further concerns or queries, please feel free to reach out to us.
Dcm 0 Reputation points

2025-04-23T23:33:15.6133333+00:00

Thank you for response.
We are using B3 plan and it has 10GB of space as documentation.
Log file size in /home/site/wwwroot/<custom_directory>is few MBs
Investigation done so far: Initially, I assumed it was a disk space issue.
Checked the folder and found: Log folder size: ~152 MB Total files: 137

As a temporary fix, I deleted some old log files. This resolved the issue temporarily.

After some research, I found these discussions: Python IOError: Errno 28 - No space left on device.

Link: Python_OSError: [Errno 28] No space left on device

Possible causes I found: Cause #1: Too many files in the directory Cause #2: Inodes are full (df -i)

However: Only ~152 MB used out of 10 GB total (App Service Plan: B3) After deleting a few files, the error disappeared, which makes both causes inconclusive

Question:

Given the above, could there be any other cause for OSError: [Errno 28] No space left on device in Azure App Service (Linux, Python 3.11)? Anyone can tell me the exact root cause ?

1 answer

Your answer

Alekhya Vaddepally 585 Reputation points Microsoft External Staff

2025-04-23T12:47:56.2966667+00:00

Hi Dcm,

The Azure app service on Linux has limited temporary storage, usually up to 1 GB in /home directory, including /home /site /wwwroot. If it fills the place (from log, temp files, etc.), then the operation of any further writing such as logging will throw this error.

Remove any unnecessary or oversized log files /from home using Kudu (App Service Advanced Tools) or through the SSH session for the container.

If you are storing the log in the file system, consider installing log rotation or retention policies to avoid bloating the disc.

Instead of writing the logs directly on the file system, we recommend sending our logs to an azure monitor or application insights, which are designed to handle large versions of the log without using the local disk space.

Alternative - Extend temporarily available space: You can consider scaling your app service plan (eg, basic to standard or higher) that increases the available disk space as part of the scheme.
https://learn.microsoft.com/en-us/azure/azure-monitor/agents/azure-monitor-agent-troubleshoot-linux-vm-rsyslog#issues
if you have any further concerns or queries, please feel free to reach out to us.
Dcm 0 Reputation points

2025-04-23T23:33:15.6133333+00:00

Thank you for response.
We are using B3 plan and it has 10GB of space as documentation.
Log file size in /home/site/wwwroot/<custom_directory>is few MBs
Investigation done so far: Initially, I assumed it was a disk space issue.
Checked the folder and found: Log folder size: ~152 MB Total files: 137

As a temporary fix, I deleted some old log files. This resolved the issue temporarily.

After some research, I found these discussions: Python IOError: Errno 28 - No space left on device.

Link: Python_OSError: [Errno 28] No space left on device

Possible causes I found: Cause #1: Too many files in the directory Cause #2: Inodes are full (df -i)

However: Only ~152 MB used out of 10 GB total (App Service Plan: B3) After deleting a few files, the error disappeared, which makes both causes inconclusive

Question:

Given the above, could there be any other cause for OSError: [Errno 28] No space left on device in Azure App Service (Linux, Python 3.11)? Anyone can tell me the exact root cause ?

Answer 1

Hi @Dcm ,

Disk Space Limits Are Not Always About Used Size, your B3 plan gives you 10 GB of storage, but that space is shared across /home, /site, and /wwwroot and some of that space is also used by the underlying container OS, logs, temp files, and other runtime operations, not just your app code or logs. Even if your custom log folder shows only 152 MB used, the total space across the full /home may still be nearing its limit due to background processes, auto-generated logs, or framework cache.

Even if the space is free, the number of inodes (file handles) might be exhausted. Every file and directory use an inode. In your case, 137 files may not seem like a lot, but it’s possible that some system-level processes or deployed packages create many small files elsewhere in /home.

Azure App Service for Linux runs on containers. These containers sometimes impose stricter file or memory quotas, especially when you use persistent write operations and you have multiple concurrent writes then there’s a burst in app usage or logging frequency So, the error could be raised not due to lack of actual space, but due to container-level quotas being breached temporarily.

Instead of continuously appending to a single file, use Python’s logging module with rotation handlers, this limits the log file size and number of files retained, preventing uncontrolled growth:

from logging.handlers import RotatingFileHandler
handler = RotatingFileHandler("log.txt", maxBytes=5*1024*1024, backupCount=5)

RotatingFileHandler docs

Rather than writing to the local file system, switch to Azure Monitor, Application Insights, or Log Analytics. These services are: Scalable, Managed, don’t use local disk and ideal for production workloads Azure Monitor Overview, Logging in Azure App Service

If your app is growing and storage needs are increasing, consider scaling from B3 to Standard or higher. Higher tiers not only offer more disk space, but also better performance and diagnostic tools. App Service Plan Tiers

If the answer is helpful, please click Accept Answer so that other people who faces similar issue may get benefitted from it.

Let me know if you have any further Queries.

Alekhya Vaddepally 585 Reputation points Microsoft External Staff

2025-04-24T09:16:47.7933333+00:00

If this answer was helpful and pointed you in the right direction, please consider clicking "Accept Answer"—it may benefit other community members reading this thread. If you have any further questions, feel free to let us know.

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Azure App Service with [Linux-based Python 3.11]: OSError [Errno 28] No space left on device

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