Re: [PATCH] btrfs-progs: docs: discourage root btrfs usage without an initramfs

[David Sterba <dsterba@suse.cz>]

On Sat, Sep 12, 2026 at 06:55:32PM +0930, Qu Wenruo wrote:
> For multi-device btrfs, device scanning is required before mounting, and
> without an initramfs it's impossible to mount a multi-device btrfs.
> 
> Even if the rootfs is a single-device btrfs, there is nothing preventing
> the end user to add a device to that btrfs, and fail the next boot.
> 
> Signed-off-by: Qu Wenruo <wqu@suse.com>
> ---
>  Documentation/mkfs.btrfs.rst | 4 ++++
>  1 file changed, 4 insertions(+)
> 
> diff --git a/Documentation/mkfs.btrfs.rst b/Documentation/mkfs.btrfs.rst
> index 0d3d6051b0e7..0bc7b7ac3808 100644
> --- a/Documentation/mkfs.btrfs.rst
> +++ b/Documentation/mkfs.btrfs.rst
> @@ -346,6 +346,10 @@ devices to scan at the time of mount.
>          before all block devices are discovered. The waiting is usually done on the
>          initramfs/initrd systems.
>  
> +        Thus using btrfs as a rootfs without an initramfs is not recommended.
> +        Adding a new device to the rootfs can easily cause the next boot to fail, as
> +        there is no way to register all devices prior to mounting.

That's not a good placement, we should write a full section how to use
btrfs without initrd and what are the caveats. A paragraph burried in
mkfs will probably never got noticed.

> +
>  .. warning::
>          RAID5/6 has known problems and should not be used in production.
>  
> -- 
> 2.55.0
>