I’m not coming up with a lot of useful (clear) results when searching for a solution to this issue.
Is it OK to simply dd the 128GB disk to the 32GB disk using count to stop after the 16GB partition was cloned?
A bit more context: I had to clone a 16GB eMMC and only had a 128GB SD around. Now I purchased a 32GB eMMC and want to clone it again. The partition holds a root filesystem for an ARMv8 device. I don’t have the 16GB eMMC anymore, that would have been the easy way out.
I’d use clonezilla
E: It’s not that it can’t be done other ways, it’s just clonezilla will work and has worked for nearly 2 decades. Plus, it’s a nice tool to throw in the toolbox once you know how to use it.
E. Why do you feel like you have to use something like dd for this particular task? Less than 16 GB of data? Ya probably could have copied it over manually by now.
It’s not an active partition/disk I want to clone. Clonezilla seems like something I need to boot into?
You can run clonezilla on your shell session, just apt install conezilla (or whatever variant you’re using) and it can do the trick. Dd will almost surely work too, but that leaves a ton of responsibility to you instead of making any sanity checks on the way. That makes dd very powerful tool and it has saved my ass a multiple times, but if you already have a working partitioning schema clonezilla has a ton of options to make your life a lot simpler and a likely a bit faster than dd.
Is it OK to simply dd the 128GB disk to the 32GB disk using count to stop after the 16GB partition was cloned?
I think it would work, but it seems a little overcomplicated, you can just use the partition paths as if and of of dd directly, as long as the output partition is not smaller than the input partition. For example dd if=/dev/sdc1 of=/dev/sdd1 bs=4M status=progress
Your method would also copy the partition table I suppose, which might be something you want under specific circumstances, but then it would be a little harder to get the count right, just taking the size of partition 1 would be wrong, because there is some space before it (where the partition table lives) and dd would start at 0. You’d need to add up the start position and the size of partition 1 instead.
Personally I would prefer making a new partition table on the new eMCC, and create a target partition on it. Then you clone the file system. This way the file system UUID will still be the same, and the fstab should still work because these days it usually refers to mounts by filesystem UUID in my experience.
If you make the target partition larger than the source partition, and you intend to use the full partition going forward you will additionally need to resize the filesystem to fit the new larger partition, for example with resize2fs.
Dd with count does work. scroll down to: Use dd, with the count option. response
https://serverfault.com/questions/439128/dd-on-entire-disk-but-do-not-want-empty-portion
If I understand the problem correctly it has a pretty simple solution that I have done before. Make a new partition on the destination and dd if=/dev/diskAsB of=/dev/diskXsY where A is the source disk and B is the source partition and X is the destination disk and Y is the destination partition. You may have to run fsck on the destination afterwards and maybe a gpt repair tool.
Honestly though, since it’s an ext filesystem, if it were me I’d just mount the source and dest and rsync.
