---
title: "Recover pfSense 2.6 from kernal panic at ZFS freeing free segment"
url: https://michalasobczak.pl/posts/recover-pfsense-2-6-from-kernal-panic-at-zfs-freeing-free-segment.html
author: "Michał Sobczak"
description: "Recently my pfSense running on the same hardware for almost 3 years, died. I tried rebooting it and removing RAM, cards etc, with no luck. So decided to bring it back from configuration backup onto new drive."
published: 2024-10-21T09:40:07.000Z
updated: 2024-10-21T09:40:07.000Z
language: en
categories: ["Technology"]
tags: ["pfSense"]
license: CC BY-NC-ND 4.0 (https://creativecommons.org/licenses/by-nc-nd/4.0/)
---
# Recover pfSense 2.6 from kernal panic at ZFS freeing free segment

Recently my pfSense running on the same hardware for almost 3 years, died. I tried rebooting it and removing RAM, cards etc, with no luck. So decided to bring it back from configuration backup onto new drive. But after few days I stared investigating this matter and I got some temporary solution to start it back.

Here is how kernel panic looks like. It says: “Attempt to query device size failed” and **“zfs: freeing free segment”**. The latter is the cause of the problem with system starting up.

![](https://michalasobczak.pl/wp-content/uploads/2024/10/image.png)

First, select “3” to escape to loader prompt:

![](https://michalasobczak.pl/wp-content/uploads/2024/10/image-1.png)

Then set:

```text
vfs.zfs.recover=1
vfs.zfs.debug=1
boot
```

![](https://michalasobczak.pl/wp-content/uploads/2024/10/image-2.png)

And you are in. However, now you need to verify if data is present, not corrupted and finally fix ZFS pool/sets as it is only a temporary fix and most probably still requires some manual work to be done.

![](https://michalasobczak.pl/wp-content/uploads/2024/10/image-3.png)

Be prepared and have recent configuration backup.