[syslinux] [PATCH 0/8] extlinux: support unmounted ext2/3/4 filesystem

Robert Yang
Thu, 25 Dec 2014 06:34:31 -0000

On 12/25/2014 01:43 PM, Ady wrote:
>
>>
>>
>> On 12/25/2014 04:33 AM, H. Peter Anvin wrote:
>>> On 12/24/2014 12:16 AM, Robert Yang wrote:
>>>> Hello syslinux,
>>>>
>>>> Merry Christmas! These patches will make extlinux work with
umounted
>>>> ext2/3/4 filesystem, for example:
>>>>
>>>> $ extlinux -i /dev/sdXN
>>>> or
>>>> $ extlinux -i file_block
>>>>
>>>> Also it can work with something like:
>>>> $ extlinux /dev/sdXN  --reset-adv
>>>> or
>>>> $ extlinux file_block --reset-adv
>>>>
>>>> We don't use a new option (I planed to use "-d"
but it is already in
>>>> use), it will check whether the target is a directory or device
and
>>>> decide what to do, it would stop and error if the device is
mounted.
>>>>
>>>> I put these patches on github so that you can easily get them
in case
>>>> you'd like to test them. (The repo's name is sys_tmp,
which avoids
>>>> confusing others, I will remove the repo when these patches are
>>>> reviewed).
>>>>
>>>> More info:
>>>> * It will use libext2fs to read and write the file.
>>>> * It will be used when the target is a extX device or file
block, and
>>>>     work as before when the target is a directory.
>>>> * It will be used for both modifing the existing adv when
>>>>     update_only == -1, and install the files to the filesystem.
>>>>
>>>> We will begin to use this feature in Yocto Project once it is
fine to
>>>> the syslinux community.
>>>>
>>>
>>> I believe we should unify this with the syslinux installer, which
is
>>> used for unmounted FAT filesystems.  Ideally we should unify that
with
>>> the extlinux installer too, but that may be a later project.
>>
>> Hello hpa,
>>
>> What does "unify that with the extlinux installer too" mean,
please ? And
>> I will add the patches to syslinux (not syslinux-mtools), and we
don't require
>> the root privilege if it is ext2/ext3/ext4 since it doesn't need
mount, what's
>> your opinion, please ?
>>
>> // Robert
>>
>>>
>>> 	-hpa
>>>
>>>
>>>
>>>
>>
>
> If I may...
>
> Note: Please do _not_ accept the following descriptions as accurate
> without confirmation that the installers are indeed currently working
> as described here.
>
> _ All the 'syslinux' commands use "device" as argument.
>
> _ The 'linux/syslinux-nomtools' installer uses system calls.
>
> _ The 'mtools/syslinux' installer requires unprivileged write
> permissions and mtools.
>
> So to continue with the same reasoning:
>
> _ An installer capable of writing to extN-formatted "devices"
would
> seemingly mean adding extN support to 'linux/syslinux-nomtools'.
This
> installer shall still be "standalone".

Hi Ady,

Thank you very much, I prefer this one, add the extN support to
linux/syslinux-nomtools, create a new "e2fs/syslinux" may make things
more complicated for the user, I will make it as:

1) If it is a extN device, then root privilege is not required.
2) Otherwise work as before.

Any suggestions is appreciated.

// Robert

>
> _ An installer capable of writing to extN-formatted "devices"
while
> requiring less permissions (i.e. unprivileged write permissions only)
> would seemingly mean an equivalent to the current 'mtools/syslinux'
> installer, but for extN. Perhaps this would mean a new
"e2fs/syslinux"
> installer? (Note that I don't mention the "libext2fs" term
here, as it
> is "too-long" and some distros might use a slightly-different
(package)
> name for the same library/capability/support/tool).
>
> This would also maintain current documentation and so-called
> "tutorials" still (mostly) relevant, avoiding confusions (to
final
> users) about the features and usage of the 'extlinux' command.
>
> Regards,
> Ady.
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