Libguestfs - May 2022 - [PATCH v2v 2/2] convert: Remove /dev/mapper/osprober-* devices left around by grub2

On Tue, May 17, 2022 at 01:10:32PM +0200, Laszlo Ersek
wrote:
> On 05/17/22 12:59, Richard W.M. Jones wrote:
> > These devices can be left around by grub2 when it runs the osprober
> > tool after we run ?/sbin/grub2-mkconfig -o /boot/grub2/grub.cfg?.
> > They are read-only mirrors of existing filesystems.  These confuse
> > later steps in conversion, specifically fstrim.
> > 
> > Reported-by: Ming Xie
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2003503
> > ---
> >  convert/linux_bootloaders.ml | 9 ++++++++-
> >  1 file changed, 8 insertions(+), 1 deletion(-)
> > 
> > diff --git a/convert/linux_bootloaders.ml
b/convert/linux_bootloaders.ml
> > index a70b65a41c..7c5fb0be3f 100644
> > --- a/convert/linux_bootloaders.ml
> > +++ b/convert/linux_bootloaders.ml
> > @@ -345,7 +345,14 @@ object (self)
> >    method remove_console = self#grub2_update_console ~remove:true
> >  
> >    method update () > > -    ignore (g#command [|
grub2_mkconfig_cmd; "-o"; grub_config |])
> > +    ignore (g#command [| grub2_mkconfig_cmd; "-o";
grub_config |]);
> > +
> > +    (* Grub2 runs osprober which sometimes leaves around read-only
> > +     * device-mapper maps covering existing filesystems.  These
> > +     * confuse later steps (especially fstrim).  So just delete
> > +     * any if found. (RHBZ#2003503).
> > +     *)
> > +    ignore (g#command [| "bash"; "-c"; "rm
-f /dev/mapper/osprober-*" |])
> >  
> >    method get_config_file () > >      grub_config
> > 
I'd like to make this change (on top):

-    ignore (g#command [| "bash"; "-c"; "rm -f
/dev/mapper/osprober-*" |])
+    ignore (g#command [| "sh"; "-c"; "rm -f
/dev/mapper/osprober-linux-*" |])

Bash might in theory not exist. I guess it's unlikely, but POSIX
defines 'sh' so we know that must exist.  It's not as if we're
using
any bash features here.

The other part of the change is that the device nodes created by the
old & buggy osprober were always called "osprober-linux-*", so we
may
as well be more specific about that.

I still cannot reproduce this bug locally.  I can force grub2-mkconfig
to run -- creating a guest like this is sufficient:

$ virt-builder rhel-8.4 --edit '/etc/sysconfig/grub:
s|^GRUB_CMDLINE_LINUX="|GRUB_CMDLINE_LINUX="resume=/dev/sda1 |'

However it doesn't reproduce the bug observed.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
live CD or over the network (PXE) and turn machines into KVM guests.
http://libguestfs.org/virt-v2v

On 05/17/22 15:09, Richard W.M. Jones wrote:
> On Tue, May 17, 2022 at 01:10:32PM +0200, Laszlo Ersek wrote:
>> On 05/17/22 12:59, Richard W.M. Jones wrote:
>>> These devices can be left around by grub2 when it runs the osprober
>>> tool after we run ?/sbin/grub2-mkconfig -o /boot/grub2/grub.cfg?.
>>> They are read-only mirrors of existing filesystems.  These confuse
>>> later steps in conversion, specifically fstrim.
>>>
>>> Reported-by: Ming Xie
>>> Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=2003503
>>> ---
>>>  convert/linux_bootloaders.ml | 9 ++++++++-
>>>  1 file changed, 8 insertions(+), 1 deletion(-)
>>>
>>> diff --git a/convert/linux_bootloaders.ml
b/convert/linux_bootloaders.ml
>>> index a70b65a41c..7c5fb0be3f 100644
>>> --- a/convert/linux_bootloaders.ml
>>> +++ b/convert/linux_bootloaders.ml
>>> @@ -345,7 +345,14 @@ object (self)
>>>    method remove_console = self#grub2_update_console ~remove:true
>>>  
>>>    method update () >>> -    ignore (g#command [|
grub2_mkconfig_cmd; "-o"; grub_config |])
>>> +    ignore (g#command [| grub2_mkconfig_cmd; "-o";
grub_config |]);
>>> +
>>> +    (* Grub2 runs osprober which sometimes leaves around read-only
>>> +     * device-mapper maps covering existing filesystems.  These
>>> +     * confuse later steps (especially fstrim).  So just delete
>>> +     * any if found. (RHBZ#2003503).
>>> +     *)
>>> +    ignore (g#command [| "bash"; "-c";
"rm -f /dev/mapper/osprober-*" |])
>>>  
>>>    method get_config_file () >>>      grub_config
>>>
> 
> I'd like to make this change (on top):
> 
> -    ignore (g#command [| "bash"; "-c"; "rm -f
/dev/mapper/osprober-*" |])
> +    ignore (g#command [| "sh"; "-c"; "rm -f
/dev/mapper/osprober-linux-*" |])
> 
> Bash might in theory not exist. I guess it's unlikely, but POSIX
> defines 'sh' so we know that must exist.  It's not as if
we're using
> any bash features here.
> 
> The other part of the change is that the device nodes created by the
> old & buggy osprober were always called "osprober-linux-*",
so we may
> as well be more specific about that.
Sure; both are good ideas.
> I still cannot reproduce this bug locally.  I can force grub2-mkconfig
> to run -- creating a guest like this is sufficient:
> 
> $ virt-builder rhel-8.4 --edit '/etc/sysconfig/grub:
s|^GRUB_CMDLINE_LINUX="|GRUB_CMDLINE_LINUX="resume=/dev/sda1 |'
> 
> However it doesn't reproduce the bug observed.
I think it's OK; you did test the fix, just on an image from someone
else. And we have confirmation from multiple independent tickets that
this symptom exists.

Thanks!
Laszlo