There are definitely still problems with btrfs compression and uboot.   If 
I take this image, update /etc/fstab to add compress=zlib, reboot to 
remount, and then run "btrfs fi defrag -c -r /" to compress the full 
filesystem, then it refuses to boot.   All I see on the console is 
"starting the kernel" and then nothing.      All the usr lights come on 
full and it sits there.

I'm still experimenting a bit.   I think an attribute can be added to the 
/boot directory to have it not compress stuff in /boot.   I want to see if 
that helps at all. 


On Wednesday, January 31, 2018 at 9:21:02 PM UTC-5, RobertCNelson wrote:
> On Wed, Jan 31, 2018 at 8:18 PM, Robert Nelson < 
> <javascript:>> wrote: 
> > On Wed, Jan 31, 2018 at 8:09 PM, Stuart Longland 
> > < <javascript:>> wrote: 
> >> On 01/02/18 10:07, Mone wrote: 
> >>> I tried with a new snapshot and it works very well. Alongside that, I 
> am 
> >>> curious and would like to learn about the BBB conversion from ext4 to 
> >>> flash filesystem. Are there any documentation/manual online that could 
> >>> explain/hint/guide through the filesystem  conversion from ext4 to 
> flash 
> >>> filesystem like btrfs? 
> >> 
> >> It's worth pointing out that btrfs is not a flash filesystem, it needs 
> a 
> >> FTL (Flash Transition Layer) to do wear levelling on a NAND flash the 
> >> same as EXT4 does. 
> >> 
> >> Your biggest hurdle is the fact that U-Boot does not understand btrfs, 
> >> so you'll need a /boot partition formatted EXT4.  Not sure that this is 
> >> likely to change, as porting btrfs to U-Boot could be a major 
> >> undertaking as it's much more complex. 
> > 
> > Actually U-Boot has btrfs support as of v2018.01 (even ZLIB 
> > compression! lzo is broken). 
> > 
> > We got a patch merged in v2018.03-rc1 that fixes (lzo compression..) 
> if you want to give it a go, use this base image: 
> it's one partition btrfs. 
> Regards, 
> -- 
> Robert Nelson 

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