[Xen-users] xenconsole: Could not open tty

[Neech Worthington <neech.worthington@xxxxxxxxxxxxxxxxxx>]

I have a problem with a guest VM that has broken mount point in its 
fstab, so I'm trying to boot a guest in to single user mode with this:
xl create -c myguest.pv 'extra="single"'

(I've also tried just editing the grub kernel command line and suffixing 
single or 1 or S on the end, and using the recovery console grub menu 
option instead, but every time I get the same outcome as below).
I see the grub screen okay, but once it has passed the timeout and 
starts to boot the kernel, I get the following message send to my terminal:
--- 8< ---
xenconsole: Could not open tty `': No such file or directory
libxl: error: libxl_exec.c:118:libxl_report_child_exitstatus: console 
child [0] exited with error status 2
--- 8< ---

A few seconds later I do get output on my terminal again, but the 
console does not appear to accept any of my inputs to press either S or 
M as per the prompting output:
--- 8< ---
 * Starting set console 
font                                             [ OK ]
 * Stopping set console 
font                                             [ OK ]
 * Starting userspace 
bootsplash                                         [ OK ]
An error occurred while mounting /var/lib/munin.
keys:Press S to skip mounting or M for manual recovery
 * Stopping userspace 
bootsplash                                         [ OK ]
 * Starting Send an event to indicate plymouth is 
up                     [ OK ]
 * Stopping Send an event to indicate plymouth is 
up                     [ OK ]
--- 8< ---

So, I have a couple of questions.

1. What is causing this xenconsole: Could not open tty error? How do I 
fix it? Is it related to me not being able to type input in to my guest 
VM console after grub?
2. How on earth do I successfully get a single user mode boot on this 
guest VM so that I can correct its fstab and get it to boot properly?
The parent hypervisor host is headless, running Ubuntu 14.04 Trusty. 
Details below:
--- 8< ---
root@host:/# dpkg -l | grep xen
rc  grub-xen 2.02~beta2-9ubuntu1                   amd64        GRand 
Unified Bootloader, version 2 (Xen version)
ii  libxen-4.4 4.4.1-0ubuntu0.14.04.3                amd64        Public 
libs for Xen
ii  libxenstore3.0 4.4.1-0ubuntu0.14.04.3                amd64        
Xenstore communications library for Xen
ii  xen-hypervisor-4.4-amd64 4.4.1-0ubuntu0.14.04.3                
amd64        Xen Hypervisor on AMD64
ii  xen-tools 4.4-1                                 all          Tools 
to manage Xen virtual servers
ii  xen-utils-4.4 4.4.1-0ubuntu0.14.04.3                amd64        XEN 
administrative tools
ii  xen-utils-common 4.4.1-0ubuntu0.14.04.3                all          
Xen administrative tools - common files
ii  xenstore-utils 4.4.1-0ubuntu0.14.04.3                amd64        
Xenstore utilities for Xen
root@host:/# uname -a
Linux host 3.13.0-44-generic #73-Ubuntu SMP Tue Dec 16 00:22:43 UTC 2014 
x86_64 x86_64 x86_64 GNU/Linux
root@host:/# lsb_release -a
No LSB modules are available.
Distributor ID:    Ubuntu
Description:    Ubuntu 14.04.1 LTS
Release:    14.04
Codename:    trusty
root@host:/#
--- 8< ---


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