[Libguestfs] boot loader detection

[Richard W.M. Jones]

On Fri, Jun 19, 2015 at 01:53:13PM +0300, Nikos Skalkotos wrote:
> Hello,
> 
> I was looking for a way to detect the installed boot loader of an image
> and I found this: https://github.com/arvidjaar/bootinfoscript
> This script will inspection a lot of things on a running system and will
> output a Report. The most interesting part is that it uses known Master
> and Volume Boot Record byte-patterns to determine the installed boot loader: 
> https://github.com/arvidjaar/bootinfoscript/blob/master/bootinfoscript#L2983-L3151
> https://github.com/arvidjaar/bootinfoscript/blob/master/bootinfoscript#L2343-L2459
> 
> Those signatures (byte patterns) are from real mode machine code but this
> code is not generated by a compiler and does not change often.
> 
> I’ve isolated and simplified the signatures database here: 
> 
> https://github.com/skalkoto/snf-image-creator/blob/develop/image_creator/bootloader.py
> 
> and I was wondering if you care to add 2 new libguestfs API methods e.g.:
> 
> char * guestfs_inspect_get_mbr_bootloader(guestfs *g)
> char * guestfs_inspect_get_vbr_bootloader(guests *g, char *device)

What is 'vbr'?

> that would return a string like “grub2”, “syslinux”, “windows”, etc.
> I can write the code.
> 
> What do you think?

I wonder if an easier and more general path here is to add the
advanced detection signatures to 'file'.  At the moment when you run
'file' on a hard drive it does some sort of detection like this:

# file -bsL /dev/sdb
DOS/MBR boot sector; partition 1 : ID=0x83, start-CHS (0x0,32,33), end-CHS (0xce,29,63), startsector 2048, 250067632 sectors, extended partition table (last)

Adding it to file means it will be available in libguestfs automatically
(via 'guestfs_file' API), and means it would be generally useful
to other people as well.

However I'm not opposed to adding it to libguestfs if for some reason
it's not possible to add this to file.

Rich.

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