On Fri, 18 Mar 2022 at 19:47, Paolo Galtieri <pgaltieri@gmail.com> wrote:
I'm having issues with a VM.

It would be useful to mention the host OS.  From the name, I guess your
VM is running Fedora 34.
 

The VM was originally created under VMware and has worked fine for a
while.  Today when I booted it up instead of seeing the usual MATE login
screen I get a login prompt:

f34-01-vm:

no matter what I enter, root or pgaltieri as login it never asks for
password and immediately says login incorrect.  While it's booting I see
several [FAILED]... messages, e.g. [FAILED] to start CUPS Scheduler

I booted the system again and this time it dropped into emergency mode. 
In emergency mode I see the following messages in dmesg:

BTRFS info (device sda2): flagging fs with big metadata feature
BTRFS info (device sda2): disk space caching is enabled
BTRFS info (device sda2): has skinny extents
BTRFS info (device sda2): start tree-log replay
BTRFS info (device sda2): parent transid verify failed on 61849600
wanted 145639 fount 145637
BTRFS info (device sda2): parent transid verify failed on 61849600
wanted 145639 fount 145637
BTRFS: error (device sda2) in btrfs_replay_log:2423 errno=-5 IO failure
(Failed to recover log tree)
BTRFS error (device sda2) open_ctree failed

I ran btrfs check in emergency mode and it came up with a lot of errors.

How do i recover the partition(s) so I can boot the system, or at least
mount them?

The underlying problem could be the physical disk that holds the VM's
virtual disk file, or a corrupt btrfs.   Avoid doing anything that would write to the 
virtual disk.  Make a backup copy of the virtual disk.  If the physical drive 
is OK, use a separate VM to mount the Fedora 34 virtual disk for repair
attempts. 

Try: https://btrfs.wiki.kernel.org/index.php/FAQ 
How do I recover from a  parent transid verify failed error?

At one time VirtualBox had issues with btrfs.  You should check for similar
reports for VMWare and btrfs.

--
George N. White III