How to mount f2fs from the same mmc partition as sqashfs?

Turris Omnia. MMC is partitioned like this:

# lsblk
loop0          7:0    0 195.7M  0 loop /overlay    <--- f2fs
mtdblock0     31:0    0   960K  0 disk 
mtdblock1     31:1    0     7M  0 disk 
mtdblock2     31:2    0    64K  0 disk 
mmcblk0      179:0    0   7.3G  0 disk 
├─mmcblk0p1  179:1    0  16.3M  0 part 
└─mmcblk0p2  179:2    0 240.3M  0 part /rom    <--- squashfs
mmcblk0boot0 179:8    0     4M  1 disk 
mmcblk0boot1 179:16   0     4M  1 disk 
zram0        254:0    0     0B  0 disk 

# losetup -a
/dev/loop0: 46727168 /dev/mmcblk0p2    <--- f2fs

mmcblk0p2 starts with a squashfs, followed by a "hidden" f2fs filesystem in the same partition.

I usually mount overlay from USB. Sometimes I need to change the extroot parameters in /etc/config/fstab from f2fs.

How do I manually mount that hidden f2fs from mmcblk0p2?


mount_root or repeat losetup command.

mount_root in a running system would probably make a mess of all the mounts.

And what is the losetup command? The usual losetup would probably expose just the squasfs, not the f2fs.

Last line after losetup command shows offset where overlay starts.

Where do I find that offset in a system that booted extroot and how do I use it?

PS: I know how to use it. losetup -o <offset>. I still don't know where to find it.

good morning...

Helloooo.... That changes every time I build a new fw image! That's ... daily.

There is no other reference about offset, you can scan for f2fs magic after end of squashfs, still hackish.

Damn it! Who tf had the ideea to put two filesystems in the same partition?? :rage:

Add another data filesystem on USB and dont break your head about them :wink:

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