Dump entire internal device memory? [duplicate]

Adding to this btrfs supports the TRIM command, which tells the underlying storage can erase the now freed area ready for the next write. Unlike spinning media, flash storage must first be erase before it can be written to again. Hence TRIM, the storage can erase the blocks ready for writing during an idle time, therefore improving performance among other reasons.

Thanks for the quick replies. I realize I may be out of luck, but want to try anyway. At least I'll learn something in the process. I just tried this with a 64GB SD card mounted to /mysd:

dd if=/dev/mmcblk0p28 of=/mysd/jolladump.img

and got this output:

dd: writing '/mysd/jolladump.img': File too large
8388609+0 records in
8388607+1 records out
4294967295 bytes (4.0GB) copied, 261.254326 seconds, 15.7MB/s

Is there a 4GB file size limit on those SD cards? Can the dump be broken into parts or is there any other solution?

4GB is an individual file size limit imposed by FAT, the default file system used on most SD cards. 64GB cards are normally preformatted with exFAT with does not have that limit but exFAT is normally not supported on Jolla so if you reformatted your SD card to FAT then you have reintroduced the 4GB limit. There is a 3rd party exFAT support installable on Jolla but I have not tried it.

You can dd in blocks. Run it again, specifying the starting offset at 4GB, writing to a new file. Repeat until you've copied the whole lot.

Or reformat your SD card to a new file system without the 4GB restriction, dump the image in one go and then copy the file to your PC..

I reformatted the SD card with exFAT using Apple's Disk Utility, but every time I try to mount it, I get:

mount: mounting /dev/mmcblk1p1 on /mysd failed: Invalid argument

When I format it as plain FAT, it works fine. The reason I had it in FAT in the first place was that Jolla doesn't support anything other than this ancient dinosaur in normal operation. I thought maybe it'd be different in recovery mode, but that doesn't seem to be the case. How did you guys manage to work with an exFAT card?