Thanks @Richard W.M. Jones!

Yes, this has been happening for us continuously after Fedora 40 upgrade.
Here is the bug I filed: 2379916 – GuestFish intermittently failing after upgrading Base image to Fedora 40

Needs some urgent help if possible, as due to fedora 39 becoming out of support for security purpose and we need to upgrade.

Thanks,
Chintan
From: Richard W.M. Jones <rjones@redhat.com>
Sent: Saturday, July 12, 2025 12:55 AM
To: Chintan Patel <chintan_orbit@outlook.com>; guestfs@lists.libguestfs.org <guestfs@lists.libguestfs.org>
Cc: libguestfs@redhat.com <libguestfs@redhat.com>
Subject: Re: GuestFish intermittently failing after upgrading Base image to Fedora 40
 
On Fri, Jul 11, 2025 at 10:41:59PM +0000, Chintan Patel wrote:
> Hi Richard,
>
> We were using LibguestFS version 1.52 on Fedora 39 and it was working as
> expected since last year, but due to the security issue and Fedora 39 is our of
> support we need to upgrade to Fedora 40 for our container base image.
>
> But after upgrading to Fedora 40, we are started experiencing intermittent
> failure on guestfish to mount the disk, sometime it is able to mount the disk
> as well execute the copy command to copy the files from disk and fails in
> middle. We are getting below failure messages in the failure.
>
>
> message
> OperationalLog: /dev/sda2: ntfs [uuid=30BC6B21BC6AE0B8]
> /dev/sda3: vfat [uuid=166A-F60E]
> /dev/sda4: ntfs [uuid=9E3C6B453C6B1793]
> GuestFish:Inspecting OS Metadata:Remote> /libguestfs/run guestfish --remote
> inspect-os
> GuestFish:Inspecting OS Metadata:Error>
> guestfish: protocol error: could not decode reply from server
> GuestFish: Retrying forInspecting OS Metadata
> GuestFish:Inspecting OS Metadata:Remote> /libguestfs/run guestfish --remote
> inspect-os
> GuestFish:Inspecting OS Metadata:Error>
> guestfish: remote: looks like the server is not running
>
>
>
> message
> GuestFish:Mount [/,/dev/sda1]:Remote> /libguestfs/run guestfish --remote --
> -mount-ro /dev/sda1 /
> GuestFish:Mount [/,/dev/sda1]:Error>
> guestfish: remote: looks like the server is not running
>
>
>
> I tried upgrading the libguesfs to the latest version 1.56.1 but still
> observing similar errors intermittently.

The error comes from
https://github.com/libguestfs/libguestfs/blob/dc218b25f0bc2704918748e4e8120ec436783e58/fish/rc.c#L423

But there's not a lot else to go on.  The protocol used:
https://github.com/libguestfs/libguestfs/blob/master/fish/rc_protocol.x

is very simple and hasn't changed in many years, so I don't know why
the XDR function would fail like this.

If you can get a proper, reliable reproducer, then I guess file a bug.

Rich.

--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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