Hi Ivan,

Thanks a lot for the clarification! That was indeed it, I was trying to mount 
the whole device.

I was able to fix the `/etc/fstab` and get my VM back up! (celebrations!)

Really appreciate all your help with this!


Fabio


‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, November 27, 2018 6:54 AM, Ivan Mitev <[email protected]> wrote:

> Hi Fabio,
>
> On 11/27/18 2:33 AM, 'Fabio' via qubes-users wrote:
>
> > Thanks for the reply Ivan.
> > I was able to mount `dom0:/dev/qubes_dom0/vm-...-private vmname` 
> > successfully, however when trying to mount 
> > `dom0:/dev/qubes_dom0/vm-...-root vmname`, I still get the `wrong fs type, 
> > bad option, bad superblock...` error.
>
> You're probably mounting the wrong partition or you are trying to mount
> the whole disk.
>
> The following steps work for me:
>
> in dom0:
>
> sudo losetup /dev/loop3 /dev/qubes_dom0/vm-fedora-26-medium-bkp-root
>
> then, attach the device to some VM like you did. In that VM run `sudo dmesg` 
> and you should see a line like
>
> [timestamp_here] xvdi: xvdi1 xvdi2 xvdi3
>
> Note: it could also be xvdj, xvdk, ... if you have other devices
> attached to the VM.
>
> There are thus 3 partitions in the device/volume you attached. You can
> see what they are with `sudo sfdisk -l /dev/xvdi`:
>
> Device Start End Sectors Size Type
> /dev/xvdi1 2048 411647 409600 200M EFI System
> /dev/xvdi2 411648 415743 4096 2M BIOS boot
> /dev/xvdi3 415744 20971486 20555743 9.8G Linux filesystem
>
> Trying to mount the first two partitions will return a "bad superblock"
> error because there isn't any recognised fs on those. Trying to mount
> the whole device (/dev/xvdi) will fail for the same reason.
>
> Mount the third partition:
>
> sudo mount /dev/xvdi3 /mnt
>
> And you should be able to fix fstab there:
>
> ll /mnt/etc/fstab
>
> -rw-r--r-- 1 root root 851 May 11 2018 /mnt/etc/fstab
>
> Then, reverse the instructions: sudo unmount /mnt, detach the device in
> the tray and remove the loopback device in dom0 (losetup -d /dev/loop3).
>
> Hope this helps...
>
> > I can confirm that I get this same error message when trying to mount any 
> > `--root` suffixed volume nested under `/dev/qubes_dom0`.
> > To confirm, I am running Qubes v4.0.
> > Any reason why the `--root` volumes in particular aren't mounting? Those 
> > are where `/etc/fstab` would be located, right?
> > Thanks again for your help!
> > Fabio
> > ‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
> > On Monday, November 26, 2018 12:11 PM, Ivan Mitev [email protected] wrote:
> >
> > > On 11/26/18 1:46 PM, 'Fabio' via qubes-users wrote:
> > >
> > > > I made an accidental edit to /etc/fstab which is causing my TemplateVM 
> > > > to timeout on boot with error Cannot connect to qrexec agent for 60 
> > > > seconds....
> > > > Is there a way to edit a particular VM's etc/fstab without booting it 
> > > > up? Can I perhaps mount it's root filesystem?
> > >
> > > for R4:
> > > https://groups.google.com/forum/#!searchin/qubes-users/losetup|sort:date/qubes-users/rWRNIt0NOc4/VaFHp42rBgAJ
> > > Alternatively the following command will configure a loopback device
> > > automatically:
> > > qvm-start --hdisk dom0:/dev/qubes_dom0/vm-...-root vmname
> > > R3.2 uses files by default instead of LVM volumes, I can't remember
> > > where they were located (/var/lib/qubes/ or something like that) but the
> > > procedure should be more or less the same.
> > >
> > > > Attempted solutions
> > > >
> > > > 1.  I've tried adding init=/bin/bash to the kernel opts, starting the 
> > > > templateVM and then running sudo xl console TEMPLATE_NAME from Dom0 but 
> > > > I did not reach a command-prompt before fstab was read and executed.
> > > >
> > > > 2.  I tried mounting the root filesystem for the TemplateVM from Dom0 
> > > > with: sudo mount /dev/qubes_dom0/vm-fedora-26-root mnt but got error 
> > > > wrong fs type, bad option, bad superblock...
> > > >
> > >
> > > It's not recommended to access VMs' files in dom0. Once you set up a
> > > loopback device and the volume pops up in the device tray, attach it to
> > > a trusted VM and fix fstab there.
> > >
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