Re: FreeBSD guest online disk resize

Van: Alexandre Biancalana <biancalana@gmail.com>
Datum: maandag, 17 november 2025 20:01
Aan: Freebsd fs <freebsd-fs@freebsd.org>
Onderwerp: FreeBSD guest online disk resize
> 
> Hello,
> 
> I am using bhyve with several VMs where the VM disks (NVMe) are stored
> on an NFS server and exported to the hypervisor. Occasionally, I need
> to expand the disks due to space constraints. I perform this expansion
> by resizing the VM disk files using the truncate command.
> 
> On Linux guests, the disk resize is immediately recognized, and the
> filesystem can be expanded online without issues.
> 
> However, on FreeBSD guests, while the NVMe layer recognizes the disk
> resize (confirmed by the appearance of the asynchronous event message
> in dmesg):
> 
> nvme2: async event occurred (type 0x2, info 0x00, page 0x04)
> 
> and `nvmecontrol devlist` correctly shows the new disk size, there is a problem.
> 
> The VM disk has no partition table and is formatted entirely with UFS
> and has a ufs label, hence geom_label is in use. Unfortunately, glabel
> list does not recognize the disk resize and still shows the old disk
> size.
> 
> I have tried the following attempts to force recognition of the new
> size without success:
> 
> Setting `sysctl kern.geom.debugflags=16`
> 
> Resetting the NVMe controller with `nvmecontrol reset nvme2`
> 
> Rescanning the disk with `camcontrol rescan nda2` and `camcontrol reprobe nda2`
> 
> Ideally, I would like to perform a disk resize that FreeBSD recognizes
> without requiring a system reboot.
> 
> Am I missing a step, or is there a recommended procedure to make
> geom_label recognize the resized disk size dynamically on FreeBSD
> guests?
>  
> 
> 
> 


What is the output of glabel list?

And next to that, does glabel refresh <device> do something useful?

Regards,
Ronald.