[OpenWrt-Devel] Current state of extroot, how to use it, what about ubi(fs)

[Imre Kaloz]

On Tue, 16 Dec 2014 16:06:27 +0100, Gergely Kiss <mail.gery at gmail.com> wrote:

Please don't top-post.

> Sorry, I haven't read that post earlier.
>
> So, is this simply about mounting an additional UBIFS partition at boot time?
>
> If so, I believe the best solution would be to extend the
> functionality of fstab with a simple (shell) script, as suggested in
> the fstab wiki:
>
> "BTRFS, JFS, *UBI* [...] are not supported in /etc/config/fstab. Use
> manual scripting."
>
> Would that be possible?
>
>
> Regards,
> Gergely
>
> On 16 December 2014 at 14:39, Flávio Silveira <fggs at terra.com.br> wrote:
>>
>> On 16/12/2014 11:23, Gergely Kiss wrote:
>>>
>>> Hi Rafał,
>>>
>>> please allow me to comment on your 2nd point as I was the one who
>>> recently published the patch to make extroot functionality work with
>>> UBIFS.
>>>
>>> "It seems that if there isn't "rootfs" MTD partition,
>>> then the code will look for "rootfs" UBI volume. The same applies to
>>> the "rootfs_data"."
>>>
>>> That's correct.
>>>
>>> "But what if my serial flash contains "rootfs" + "rootfs_data"
>>> partitions and I still want to use some UBI volume on another flash
>>> (NAND one)?"
>>>
>>> I'm not sure I understand what you mean here. Are there any devices
>>> out there with multiple flash chips on-board? As far as I know, UBI
>>> cannot work on top of block devices (eg. USB flashes, SD cards), only
>>> raw flash chips so I can't really imagine what exact use-case you
>>> mean. Could you please clarify?
>>>
>>>
>>> Thanks,
>>> Gergely
>>>
>>>
>>> On 16 December 2014 at 11:00, Rafał Miłecki <zajec5 at gmail.com> wrote:
>>>>
>>>> I've spent few hours today trying to understand extroot. I've failed :(
>>>>
>>>> Of course I was trying to use wiki pages:
>>>> http://wiki.openwrt.org/doc/howto/extroot
>>>> http://wiki.openwrt.org/doc/uci/fstab
>>>>
>>>> 1) Main question
>>>> Is the following sentence true at all?
>>>>>
>>>>> The configuration of extroot is very simple and is done entirely in
>>>>> /etc/config/fstab.
>>>>
>>>> It seems that /etc/init.d/fstab uses "block umount" and "block mount"
>>>> only. I was reading the source code (fstools-2014-12-15/block.c) and
>>>> it seems that "block mount" doesn't really handle extroot at all.
>>>>
>>>> I think some kind of extroot support is provided in "block extroot",
>>>> but I don't fully understand it. It seems to be looking for partitions
>>>> "rootfs" and then "rootfs_data" ignoring whatever is set in
>>>> /etc/config/fstab. If "mount extroot" is really supposed to be used,
>>>> is there any way to point some external device (without MTD
>>>> partitions) as extroot? I got confused.
>>>>
>>>> 2) UBI and UBIFS support
>>>>
>>>> I guess it's too new to be documented and I don't understand it much
>>>> from the code. It seems that if there isn't "rootfs" MTD partition,
>>>> then the code will look for "rootfs" UBI volume. The same applies to
>>>> the "rootfs_data".
>>>> But what if my serial flash contains "rootfs" + "rootfs_data"
>>>> partitions and I still want to use some UBI volume on another flash
>>>> (NAND one)?
>>>>
>>>> --
>>>> Rafał
>>>
>>> _______________________________________________
>>> openwrt-devel mailing list
>>> openwrt-devel at lists.openwrt.org
>>> https://lists.openwrt.org/cgi-bin/mailman/listinfo/openwrt-devel
>>
>>
>> Hi,
>>
>>   I think this is where this discussion started and Rafal explains a bit
>> more about the hardware:
>> https://lists.openwrt.org/pipermail/openwrt-devel/2014-December/029717.html
>>
>> Regards,
>>   Flavio

Rafal, what about mtdconcat?


Imre
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