[Gta04-owner] ***UNCHECKED*** Re: suggestions for rootfs

[H. Nikolaus Schaller]

> Am 03.02.2017 um 08:43 schrieb H. Nikolaus Schaller <hns at goldelico.com>:
> 
> Hi Andreas,
> 
>> Am 02.02.2017 um 23:26 schrieb Andreas Kemnade <andreas at kemnade.info>:
>> 
>> Hi Nikolaus,
>> 
>> On Wed, 1 Feb 2017 07:16:45 +0100
>> "H. Nikolaus Schaller" <hns at goldelico.com> wrote:
>> 
>>> I am not sure. We use ubifs and AFAIK it "compresses" by using less
>>> padding bytes for many small files. But this just means it uses the
>>> blocks more efficiently. In fact it looks as if I can get ca. 550MB
>>> from µSD into the 460 MB available.
>>> 
>>> But I have not read about real compression. Could virtually extend the
>>> available space by factor 2 (since so many files are plain ASCII).
>>> 
>>> Anyone knows how to compress ubifs?
>>> 
>> mkubifs -x ...
>> mount -o compr=...
>> 
>> zlib and lzo are available
> 
> thanks!
> 
> I have done some research, but we create the ubifs differently:
> 
> 			ubiformat -y /dev/mtd4
> 			ubiattach /dev/ubi_ctrl -m 4
> 			ubimkvol /dev/ubi0 -N gta04-rootfs -m &&
> 			mkdir -p /mnt/nand &&
> 			mount -t ubifs ubi0:gta04-rootfs /mnt/nand
> 
> And I have not found any option to control compression for
> ubiformat, ubiattach or ubimkvol (where I had expected it).
> 
> BTW, these tools are really badly documented. Only --help is
> available :(
> 
> Well, I think I have a hint: http://www.linux-mtd.infradead.org/faq/ubifs.html
> section "Is it OK to mount empty UBI volumes?" says:
> 
> "Yes, it is OK to mount empty UBI volumes, i.e. the volumes which contain only 0xFF bytes. In this case UBIFS formats the media automatically with default parameters (journal size, compression, etc)."
> 
> and gives sample code:
> 
>> # Create an UBI volume - the created volume will be empty
>> ubimkvol /dev/ubi0 -N test_volume -s 10MiB
>> 
>> # Mount UBIFS - it will automatically format the empty volume
>> mount -t ubifs ubi0:test_volume /mnt/ubifs
> 
> So this means that it could suffice to initially mount with -o compr=lzo
> which should create a compressed image and afterwards it should simply "know"
> about compression. Let's give this theory a try.

Well, it works using -o compr=lzo but makes no difference. Either compression
is already turned on or this method of creating a compressed ubifs does not
work.

BR,
Nikolaus

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