OpenZFS 2.3.4 Brings Linux 6.16 Kernel Compatibility, "zfs rewrite" Command

Written by Michael Larabel in Linux Storage on 25 August 2025 at 08:30 PM EDT. 28 Comments

OpenZFS 2.4-rc1 was released a few days ago with faster encryption performance using AVX2 and other enhancements. For those just looking for bug fixes and expanded Linux kernel compatibility, OpenZFS 2.3.4 is out today as the newest stable point release.

OpenZFS 2.3.4 brings support for the latest Linux 6.16 stable kernel where as the prior 2.3.3 release tapped out at Linux 6.15. OpenZFS 2.3.4 continues to support back to the Linux 4.18 kernel as well as FreeBSD 13.3 and newer, including the upcoming FreeBSD 15.0.

👁 zfs rewrote sub-command

Making it into OpenZFS 2.3.4 is also the new zfs rewrite sub-command. This is an interesting addition and the zfs rewrite sub-command should be able to address a range of use cases. The merge elaborates:

"Motivation and Context

For years users were asking for an ability to re-balance pool after vdev addition, de-fragment randomly written files, change some properties for already written files, etc. The closest option would be to either copy and rename a file or send/receive/rename the dataset. Unfortunately all of those options have some downsides.

Description

This change introduces new zfs rewrite subcommand, that allows to rewrite content of specified file(s) as-is without modifications, but at a different location, compression, checksum, dedup, copies and other parameter values. It is faster than read plus write, since it does not require data copying to user-space. It is also faster for sync=always datasets, since without data modification it does not require ZIL writing. Also since it is protected by normal range range locks, it can be done under any other load. Also it does not affect file's modification time or other properties."

OpenZFS 2.3.4 also brings a few FreeBSD fixes, various packaging updates, and other mostly small bug fixes.

Downloads and more details on OpenZFS 2.3.4 via GitHub.