Zfs on Kenno's Open Note

How to Rename a ZFS Pool

Wed, 30 Jul 2025 21:01:42 +1000

I’ve been a happy ZFS user for years, appreciating its robustness and features. Yet, in all that time, I’d never had to rename a pool. That changed today. Whether it’s for better organization, a server migration, or just because you’ve had a change of heart about a name, renaming a ZFS pool is a task that might pop up when you least expect it.

I needed to rename my pool from anime35 to anime36. I was pleasantly surprised to find the process is incredibly simple and elegant, which is what I’ve come to expect from ZFS.

How to import ZFS pool with duplicated pool names

Sat, 14 Dec 2024 18:32:22 +1100

If you use ZFS as the file system, you probably already know that tank is the most common name for ZFS pools. That also applies to me, I do name most of my ZFS pools as tank as the default. There is no issue with that name, however, since ZFS’s pool name must be unique, this means I couldn’t import or have multiple ZFS pools with the name tank on a system.

Expand ZFS partition to use entire disk

Tue, 12 Nov 2024 10:09:20 +1100

This is just a quick note to jot down what I did to resize and expand a ZFS partition to entire disk. I never had to do this before; it tured out it was quite easy.

First ensure that the autoexpand option is set on the zpool. Then, stop the VM in order to resize the disk volume.

[root@phnomaural ~]# zpool set autoexpand=on immich

[root@phnomaural ~]# poweroff
[root@phnomaural ~]# Connection to phnomaural closed by remote host.

The original size of ZFS disk was 256 GiB, and it has been increased to 512 GiB. This was done by stopping the VM running on XCP-ng, and go to the disk and change the size to 256 GiB.

How to rebuild initramfs on Fedora

Wed, 21 Aug 2024 21:42:21 +1000

Earlier today while performing the update on my Fedora desktop, I encountered an issue with the new kernel update. As a result, the initramfs was not generated for the new installed kernel. So, I’ll share with you how to rebuild or generate the initramfs while fixing real issue on my Fedora workstation.

First, here is an output showing the source of the issue. It might not be clear of what’s going on, but that’s okay as it’s not the main focus of this blog post.

How to Remove ZFS Meta Data on FreeBSD

Wed, 26 May 2021 23:02:42 +1000

It’s been quite a while since I last posted something here. It’s not that I haven’t come across many issues in tech, it’s just that I haven’t had enough time to write anything.

So I’m going to share how to easily clear the ZFS metadata on a disk previously used in a ZFS pool. Here is an example - I have an external drive, and it is detected as /dev/da0 when plugged into a FreeBSD server. Though I don’t remember having used it as a member of a ZFS pool called tank, the following output does show that it is the case:

Using ZFS on an External Drive

Thu, 12 Nov 2020 22:52:58 +1100

I’m a fan of ZFS filesystem. It’s so good that I also use ZFS on most my Linux machines, though it’s painful at time when the ZFS kernel modules fail to compile. Why I like it so much comparing to other file system such as XFS, EXT4, BTRFS? ZFS allows me to quickly do snapshots and efficiently send snapshots over the network, and my nas runs FreeBSD which support ZFS natively.

Replacing a Disk in a Zpool

Sun, 20 Sep 2020 11:51:35 +1000

ZFS is one of my favorite file systems. I use it at home on my nas server (running FreeBSD) as well as my Fedora 32 desktop. Today, I’m going to show you (and my future self) how to replace a (faulty) disk in a Zpool.

The server I’ll be working on is nas2 and the pool is tank.

List the status of the current pool.

Password:
root@nas2:~ # zpool status tank
  pool: tank
 state: DEGRADED
status: One or more devices could not be opened.  Sufficient replicas exist for
        the pool to continue functioning in a degraded state.
action: Attach the missing device and online it using 'zpool online'.
   see: http://illumos.org/msg/ZFS-8000-2Q
  scan: resilvered 472K in 0 days 00:00:02 with 0 errors on Sun Aug 23 16:17:21 2020
config:

        NAME                      STATE     READ WRITE CKSUM
        tank                      DEGRADED     0     0     0
          mirror-0                DEGRADED     0     0     0
            diskid/DISK-Z4Z46MXG  ONLINE       0     0     0
            620907994788427922    UNAVAIL      0     0     0  was /dev/diskid/DISK-Z1E4ZCM2
          mirror-1                ONLINE       0     0     0
            diskid/DISK-Z1E5PFCH  ONLINE       0     0     0
            diskid/DISK-Z4Z46XQP  ONLINE       0     0     0

errors: No known data errors

From the above output, we can see that one of the disk in mirro-0 vdev was missing. (In fact, it has been removed prior to the system rebooted. I also inserted a new disk to the system.)

Remove Kernels on Fedora

Sun, 26 Apr 2020 00:11:01 +1000

I’m still running Fedora 31 on my main desktop though Fedora 32 beta has been out for a while. The only reason that stops me from jumping to F32 now is because ZFS 0.8.3 is not compatible with the kernel 5.6.* on F32. Rumor has it, ZFS 0.8.4 will support kernel 5.6.

Tonight, while doing the system update with sudo dnf update -y on F31 desktop, I noticed that the kernel for F31 is now kernel-5.6.6-200.fc31.x86_64. Wait, what? I didn’t interrupt the update process, and let it run till finish.

Fedora 30 Beta With ZFS Support

Thu, 18 Apr 2019 19:18:30 +1000

Up until today, I have been running Fedora 29 with the kernel 4.9. The current version of the kernel on Fedora 29 is 5.0. However, I had to stick with the 4.20 version for a very long while due to a thing I did a short while back. So what is that thing? Well, at one point ZFS (stable) no stopped working with the new kernel on Fedora 29. At then, I had a choice to either keep running older version of the kernel or trying out the new version of ZFS (testing). I opped for the second option. When Fedora 29 bumped its kernel to 5.0, unfortunately, the testing ZFS didn’t support this version of the kernel.

ZFS Testing on Fedora

Thu, 31 Jan 2019 11:37:20 +1100

When Fedora release kernel 4.20.*, the ZFS 0.7.12 could no longer compiled. Accoriding to the ZFS release page at Github zfs-0.7.12 is only compartible iwth kernels 2.6.32 - 4.19.

At first I was going to just wait for the 0.8.0 release, and continue to use kernel 4.19. However, Fedora keeps releasing the updates of kernel 4.20. As of this writing, the current version of the kernel on Fedora 29 is 4.20.6-200. At the same time, zfs-0.8.0 is still not yet released.

Upgrading Freebsd 11.2 to 12.0-RELEASE

Wed, 12 Dec 2018 21:07:08 +1100

FreeBSD 12.0-RELEASE was released today, and that means it’s time to upgrade 2 of FreeBSD 11.2 machines to this latest version.

One of my FreeBSD boxes is a desktop used at work, and the upgrade went well without any issues. In this post, I’m going to document how the upgrade is done on my nas server at home.

First ensure that the FreeBSD is up to date:

root@nas:~ # freebsd-update fetch
src component not installed, skipped
Looking up update.FreeBSD.org mirrors... 2 mirrors found.
Fetching metadata signature for 11.2-RELEASE from update1.freebsd.org... done.
Fetching metadata index... done.
Inspecting system... done.
Preparing to download files... done.

No updates needed to update system to 11.2-RELEASE-p6.

Begin to perform the upgrade:

Upgrading my nas from FreeBSD 11.1-RELEASE to 11.2-RELEASE

Sat, 30 Jun 2018 20:33:54 +0000

FreeBSD 11.2-RELEASE was released a few days ago. This means it’s time to upgrade the FreeBSD running on my nas.

For the most part, this was all what I did:

# freebsd-update -r 11.2-RELEASE upgrade
# freebsd-update install
# reboot
# freebsd-update install

After it’s been upgraded, I also need to update the Zpool.

root@nas:~ # zpool status
  pool: zroot
 state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
        still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
        the pool may no longer be accessible by software that does not support
        the features. See zpool-features(7) for details.
  scan: scrub repaired 0 in 0h0m with 0 errors on Tue Jan 23 23:54:42 2018
config:

        NAME        STATE     READ WRITE CKSUM
        zroot       ONLINE       0     0     0
          gpt/zfs0  ONLINE       0     0     0

errors: No known data errors

Let’s upgrade the zpool zroot as suggested:

How to extend ZFS partition

Sun, 11 Mar 2018 11:37:07 +0000

I have a FreeBSD server which used to run of a smaller SSD drive. When replaced with a larger capacity SSD by using dd command to clone the disk, there is free space allocated. I want to extend the existing zroot pool to use this space. The following describes how I achieve this with the help of a forum post.

Let’s list some information about the zroot pool:

root@nas:~ # zfs list zroot
NAME    USED  AVAIL  REFER  MOUNTPOINT
zroot  4.88G  50.8G   144K  none

List the partition scheme of the drive I’d like to extend my zroot zpool with:

FreeBSD Recover GTP Table

Sat, 03 Feb 2018 22:30:18 +0000

Recently one of my servers that runs FreeBSD 11.1 keeps hanging on boot. Usually, the 2nd hard reboot will fix it. The root file system on this server is using ZFS and the ZFS pool report it as healthy.

nas:~ # zpool status                                                                                                [136/462]
  pool: zroot                                                                                                                     
 state: ONLINE                                                                                                                    
  scan: scrub repaired 0 in 0h0m with 0 errors on Tue Jan 23 23:54:42 2018                                                        
config:                                                                                                                           
                                                                                                                                  
        NAME        STATE     READ WRITE CKSUM                                                                                    
        zroot       ONLINE       0     0     0                                                                                    
          gpt/zfs0  ONLINE       0     0     0                                                                                    
                                                                                                                                  
errors: No known data errors

So I’ve been reluctant to do anything about it. Until tonight, when I accidentally list the partition of that drive (ada4):

ZFS on Linux is now available for Fedora 27

Tue, 19 Dec 2017 00:34:26 +0000

My main machine at home has been upgraded from Fedora 26 to 27 since the day the 27 was released. Everything has been working great, except the ZFS file system. I’m a ZFS-believer and I store my important files on ZFS-based storage.

For a while there was no repository for Fedora 27 provided by zfsonlinux, until 6 days ago.

I have been using packages provided for Fedora 26 as work around solution. If you’ve been using the ZFS packages for Fedora 26, you can upgrade to the ones for Fedora 27 now.

Zpool Not Automatically Mounted on Boot on Fedora

Tue, 20 Dec 2016 15:12:40 +0000

I love ZFS, but there is something that has annoyed me for quite sometimes – the zpool doesn’t get automatically mounted on boot. To work around this, I had to login as root and run:

# zpool import tank

to import tank pool before I login with my normal user account.

Well, I finally found a solution. This is what’s written on zfsonlinux/zfs WIFI about Fedora specifically:

Systemd Update:

When upgrading to the zfs-0.6.5.8 release it’s recommended that users manually reset the zfs systemd presets. Failure to do so can result in the pool not automatically importing when the system is rebooted.

Install ZFS on Fedora 25 with kernel 4.8.13-300

Thu, 15 Dec 2016 23:08:52 +0000

After I had my Fedora 24 upgraded to 25 on my desktop, ZFS no longer worked. I tried to remove zfs package and reinstalled; it didn’t work.

Here’s how I got it working after trying many things. There could be a different way to fix it, though.

Let’s check the version of the kernel:

[root@sangkae ~]# uname -r
4.8.13-300.fc25.x86_64

Check if spl, zfs are already installed:

[root@sangkae ~]# dnf info spl
Last metadata expiration check: 1:01:18 ago on Thu Dec 15 22:42:25 2016.
Installed Packages
Name        : spl
Arch        : x86_64
Epoch       : 0
Version     : 0.6.5.8
Release     : 1.fc25
Size        : 48 k
Repo        : @System
From repo   : zfs
Summary     : Commands to control the kernel modules
URL         : http://zfsonlinux.org/
License     : GPLv2+
Description : This package contains the commands to verify the SPL
            : kernel modules are functioning properly.

[root@sangkae ~]# dnf info zfs
Last metadata expiration check: 1:01:26 ago on Thu Dec 15 22:42:25 2016.
Installed Packages
Name        : zfs
Arch        : x86_64
Epoch       : 0
Version     : 0.6.5.8
Release     : 1.fc25
Size        : 808 k
Repo        : @System
From repo   : zfs
Summary     : Commands to control the kernel modules and libraries
URL         : http://zfsonlinux.org/
License     : CDDL
Description : This package contains the ZFS command line utilities.

Manually install spl, dkms:

FreeBSD upgrade pool zroot

Tue, 27 Sep 2016 21:09:39 +0000

Today I successfully upgraded my FreeBSD home nas server from 10.3 to 11.0. This is the final release of version 11.0, though the official announcement is expected to be made on September 28.

After the system upgrade, I need to also upgrade the 2 zpools (tank and zroot) so they can have new features. Upgrading tank was easy, all I needed to do was running this command:

# zpool upgrade tank
This system supports ZFS pool feature flags.

Enabled the following features on 'tank':
  sha512
  skein

For zroot, in addition to running the above command (by replacing the actually zpool name to zroot), I also need to update the boot code.

Losing ZFS storage for Docker

Sun, 11 Sep 2016 01:09:40 +0000

I use ZFS as a storage driver for docker engine running on my machine. Today after my machine rebooted from a crash, yes Linux system crashes too, I notice that all my docker images and containers disappeared.

~ ❯❯❯ docker ps
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES
~ ❯❯❯ docker ps -a
CONTAINER ID        IMAGE               COMMAND             CREATED             STATUS              PORTS               NAMES

First thing came to my mind was “did I accidentally destroy docker zfs data set last night?”

ZFS zpool upgrade

Mon, 14 Dec 2015 00:56:26 +0000

I’m running ZFS on Fedora 23 and I notice that there’re new features which can be enabled in the existing pool.

# zpool status
  pool: tank
 state: ONLINE
status: Some supported features are not enabled on the pool. The pool can
        still be used, but some features are unavailable.
action: Enable all features using 'zpool upgrade'. Once this is done,
        the pool may no longer be accessible by software that does not support
        the features. See zpool-features(5) for details.
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            sdb     ONLINE       0     0     0
            sdc     ONLINE       0     0     0

errors: No known data errors

Get the ZFS version for tank’s pool:

ZFS on CentOS

Tue, 08 Oct 2013 07:55:46 +0000

First we need to add the ZFS on Linux repository to our system by installing a zfs-release package as shown below:

$ sudo yum localinstall --nogpgcheck http://archive.zfsonlinux.org/epel/zfs-release-1-3.el6.noarch.rpm
$ sudo yum install zfs

Once, zfs has been installed, we can create a storage pool. There’re many RAID configuration to choose from, and I’m not going to get into it. However, if you want to learn more, you can read this ZFS Administration article which explains in great detail about ZFS RAID(Z).

Changing ZFS pool to use disk ID instead of disk assignment

Fri, 20 Sep 2013 06:49:51 +0000

This what I have:

# zpool status
  pool: tank
 state: ONLINE
  scan: none requested
config:

        NAME        STATE     READ WRITE CKSUM
        tank        ONLINE       0     0     0
          raidz1-0  ONLINE       0     0     0
            sdb     ONLINE       0     0     0
            sdc     ONLINE       0     0     0
            sdd     ONLINE       0     0     0

To convert the pool to use disk’s ID instead of device files such as /dev/sda, we need to export the storage pool.