Re: [Xen-devel] [PATCH] failing to set value to 0 in Grub2ConfigFile

[Steven Haigh <netwiz@crc.id.au>]

I've had a tinker with the patch - I don't have a Fedora build system 
atm - so I just edited the file on the Dom0 and removed the pyc/pyo 
files. Same issue:

    pyGRUB  version 0.6
 
┌────────────────────────────────────────────────────────────────────────┐
 │ Fedora (5.2.6-200.fc30.x86_64) 30 (Thirty)                         
    │
 │ Fedora (0-rescue-ee4b18b1898e4bf2b36ff71077b23b5e) 30 (Thirty)     
    │
 │                                                                    
    │
 │                                                                    
    │
 │                                                                    
    │
 │                                                                    
    │
 │                                                                    
    │
 │                                                                    
    │
 
└────────────────────────────────────────────────────────────────────────┘
     Use the ^ and v keys to select which entry is highlighted.
     Press enter to boot the selected OS, 'e' to edit the
     commands before booting, 'a' to modify the kernel arguments
     before booting, or 'c' for a command line.

The rescue entry is selected in the above example.

My crappy hack has been to edit /usr/libexec/xen/bin/pygrub and add 
sel=0 as follows:

    def image_index(self):
        if isinstance(self.cf.default, int):
            sel = self.cf.default
        elif self.cf.default.isdigit():
            sel = int(self.cf.default)
            sel = 0
        else:

I know this is horrible!

I'm still disabling BLSCFG in /etc/default/grub - otherwise the pygrub 
menu is completely empty.

I don't know what the solution is right now - but I do somewhat agree 
with ignoring anything inside an if statement in grub.cfg - as the 
logic is ignored anyway. Do you still need to read the grubenv in doing 
this?

I assume the read for grubenv is to get the 'saved_entry' value?

Steven Haigh

📧 netwiz@crc.id.au     💻 https://www.crc.id.au
📞 +613 9001 6090       📱 +614 1293 5897


On Wed, Aug 14, 2019 at 7:51 AM, "YOUNG, MICHAEL A." 
<m.a.young@durham.ac.uk> wrote:
> On Tue, 13 Aug 2019, Andrew Cooper wrote:
> 
>>  On 13/08/2019 22:02, YOUNG, MICHAEL A. wrote:
>>>  I have been looking at the pygrub code to see if it is possible to 
>>> cope
>>>  with grub files with BLSCFG and spotted this minor issue in 
>>> GrubConf.py
>>>  where the code intends to replace ${saved_entry} and ${next_entry} 
>>> with 0
>>>  but doesn't succeed.
>>> 
>>>  Signed-off-by: Michael Young <m.a.young@durham.ac.uk>
>> 
>>  Ah - this looks suspiciously like it might be the bugfix for an 
>> issue
>>  reported by Steven.
>> 
>>  Steven - do you mind giving this patch a try for your "Fedora 30 
>> DomU -
>>  pygrub always boots the second menu option" problem?
> 
> Sadly I don't think it is that simple and to it properly would require
> parsing if clauses in the grub file and also reading variables from 
> the
> grubenv file.
> 
> I do however have an idea which might work which is to ignore 
> anything in
> if clauses, read the grubenv file (which I now have a hacky way of 
> doing)
> and treating the value of next_entry or saved_entry as the setting for
> the default kernel to pick. If I finish a patch that does this I will 
> post
> it on the list, but I very much doubt it will be of commitable 
> quality.
> 
>  	Michael Young
> 
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> Xen-devel@lists.xenproject.org
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