On Mon, Nov 23, 2020 at 01:38:34AM +0530, Sreyan Chakravarty wrote: > Hi, > > I use LVM on top of LUKS. > > My entire root file system is on a logical volume. I have no seperate home > or swap partitions. > > I would like to know how can I clone this logical volume to my external > hard disk. > > I have seen commands like : > > dd if=/dev/vg/root_lv of=/mnt/exthdd bs=64k conv=noerror,sync > status=progress > > I have a couple of questions about this: > > 1) Why use noerror and sync? > > noerror might give me a corrupted image and sync is just going to increase > the size of my image with padding. > > Why use them? > > 2) What is rationale behind block size? > > Will using 4M block size instead of 64K give me a different image? I need > my image to be an EXACT COPY.
Does dd write a complete final block to the destination. If so, the image would not be an exact copy unless the source size is an exact multiple of the blocksize. Gdisk reports my root filesystem is 240197632 1K blocks long. $ factor 240197632 240197632: 2 2 2 2 2 2 2 2 2 2 2 2 2 109 269 So 2^13, or 8KB is the largest block size where input and output would match. Again, this assumes dd writes a full final block. Possibly a bad assumption Jon -- Jon H. LaBadie jo...@jgcomp.com _______________________________________________ users mailing list -- users@lists.fedoraproject.org To unsubscribe send an email to users-le...@lists.fedoraproject.org Fedora Code of Conduct: https://docs.fedoraproject.org/en-US/project/code-of-conduct/ List Guidelines: https://fedoraproject.org/wiki/Mailing_list_guidelines List Archives: https://lists.fedoraproject.org/archives/list/users@lists.fedoraproject.org
