Truncate unallocated space from SD card

Asked Oct 06 '23 at 07:49

Active Oct 06 '23 at 07:49

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I have an Armbian system SD card that I want to copy to another device. The system was 16GB but was previously imaged to 64GB card and now it is to big to handle for me. Is it any way to truncate unallocated space from the SD card?

asked Oct 06 '23 at 07:49

user3742046

Does this answer your question? Utility to TRIM unallocated space on drive – Marcus Müller Oct 06 '23 at 07:53
2

Though honestly, why not just take an image of the first 14.4 GB and be done with it? – Marcus Müller Oct 06 '23 at 07:55
(you might want to run fstrim on the ext4 file system first, but that's about it.) – Marcus Müller Oct 06 '23 at 08:12
It fails with "the discard operation is not supported" – user3742046 Oct 06 '23 at 08:40
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Then the SD card literally doesn't support truncation, and you'll have to overwrite with zeros, just to get an image containing zeros. So, really, just do an image of the first 14.4 GB of your SD card and be done. It makes no difference! – Marcus Müller Oct 06 '23 at 08:42
I think the OP was never thinking about "sparsing". Apparently he really just mean "(re-)shortening", which can easily done with dd or even head. (Use fdisk -l to find out where the last/only partition ends.) – Tom Yan Oct 06 '23 at 13:04
@MarcusMüller FWIW, most SD cards do have discard/TRIM-like command(s), and they often result in "read zero". It's just most if not all USB reader does not implement any command translation (from e.g. SCSI UNMAP) in their bridge chip. – Tom Yan Oct 06 '23 at 13:11
@TomYan true! I remember that being a more common problem when USB FullSpeed readers were still the main thing in the low-cost market! Had totally forgotten about that layer of translation! – Marcus Müller Oct 06 '23 at 14:52

Truncate unallocated space from SD card

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