[syslinux] [RFC] make extlinux work without mount the filesystem

[Robert Yang]

On 11/21/2014 03:17 PM, Ady wrote:
>
>>
>>
>> On 11/21/2014 02:33 PM, H. Peter Anvin wrote:
>>> On 11/20/2014 10:21 PM, Robert Yang wrote:
>>>>
>>>> which can copy files into test.img without mount it, for example:
>>>> $ mke2fs -t ext3 -d <rootfs_dir> -F test.img
>>>>
>>>> I'd like to make extlinux can work without mount the filesystem (use
>>>> libext2fs), is it possible for extlinux, please ? And is such a patch
>>>> acceptable, please ? (Add a "-d/--device <device>" option, and the
>>>> option is optional).
>>>>
>>>
>>> I would definitely accept such a patch.  It probably makes more sense in the
>>> "syslinux" installer rather than "extlinux", since the former already operates
>>> on an unmounted filesystem.
>>
>> Great, thanks for the reply, I will do more investigations on syslinux/extlinux,
>> and ask for help or send a draft design later.
>>
>> // Robert
>>
>>>
>>> I would also love to unify the FAT implementation.
>>>
>>>       -hpa
>>>
>>>
>>>
>>>
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>
> Let's not forget that:
>
> _ The 'extlinux' command already accepts a "--device <dev>" parameter.

Ah, yes, what I had tried is the extlinux on Ubuntu 14.04.1, which is
4.05 and didn't have --device, but the git repo has, I will use another
option name.

>
> _ There are several "syslinux installers" (for BIOS) and there should
> be a certain degree of convergence / consistency between them,
> specially regarding the command line arguments (aka. "usage"). This
> convergence should include the Windows-based and DOS-based installers
> as much as possible. Conflicting arguments between the different
> SYSLINUX installers, or breaking backwards compatibility (in terms of
> users' usage, or even regarding procedures and documentation) should be
> minimized as much as possible.
>
> _ Under Linux, we have the (./bios/linux/) 'syslinux-nomtools'
> installer, the (./bios/mtools/) 'syslinux' installer, and the
> (./bios/extlinux/) 'extlinux' installer. They have different
> requirements, different dependencies, and different capabilities, so
> one installer might be more adequate for a certain situation / use-case
> than others.
>
> _ The Windows-based and DOS-based SYSLINUX installers currently do not
> support all the options / capabilities of the Linux-based installers
> (mostly because no one invested time on fully implementing them), but
> they also include capabilities that are not included in the Linux-based
> installers.
>
> _ Whichever additional / proposed / new arguments to be added to any
> one of the SYSLINUX installers, they shall not conflict with arguments
> already included in anyone of the installers (e.g. "-a", "-m"...).
>
> _ Let's be careful not to allow a "too-easy" execution of code that
> could be potentially harmful. The SYSLINUX installers are frequently
> used by common users with no knowledge nor understanding. If a SYSLINUX
> installer could potentially be used "too-freely" and without special
> requirements / permissions / care, then relevant warnings (and perhaps
> even more than that) should be available to the user before a
> potentially harmful action is actually applied.
>

Thanks, I need more investigations to understand these.

// Robert

> Regards,
> Ady.
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>