I shrank the original NTFS partition on a 1TB USB drive to make room for an encrypted FAT32 filesystem after it. The partition table is:
# fdisk -l /dev/sdb Disk /dev/sdb: 931.5 GiB, 1000204885504 bytes, 1953525167 sectors Units: sectors of 1 * 512 = 512 bytes Sector size (logical/physical): 512 bytes / 4096 bytes I/O size (minimum/optimal): 4096 bytes / 33553920 bytes Disklabel type: dos Disk identifier: 0x6bc6bcdc Device Boot Start End Sectors Size Id Type /dev/sdb1 2048 1302349823 1302347776 621G 7 HPFS/NTFS/exFAT /dev/sdb2 1302349824 1953521663 651171840 310.5G c W95 FAT32 (LBA) # and I left a gap at the end for a 1MB alignment (and future-proofing). After running badblocks on sdb2, I created a LUKS container and made the FAT32 filesystem: # cryptsetup luksFormat /dev/sdb2 […] # cryptsetup open --type luks /dev/sdb2 thequiz Enter passphrase for /dev/sdb2: # mkdosfs -v -i 20141210 -F 32 -n quiz02 /dev/mapper/thequiz mkfs.fat 4.1 (2017-01-24) mkfs.fat: warning - lowercase labels might not work properly with DOS or Windows /dev/mapper/thequiz has 255 heads and 63 sectors per track, hidden sectors 0x0000; logical sector size is 512, using 0xf8 media descriptor, with 651106305 sectors; drive number 0x80; filesystem has 2 32-bit FATs and 64 sectors per cluster. FAT size is 79488 sectors, and provides 10171051 clusters. There are 64 reserved sectors. Volume ID is 20141210, volume label quiz02 . # cryptsetup luksClose thequiz # However, I now get this logged: device-mapper: table: 254:1: adding target device sdb2 caused an alignment inconsistency: physical_block_size=4096, logical_block_size=512, alignment_offset=0, start=33553920 Two of these lines came when I formatted the filesystem, and two more when I reopened the container in order to: # cryptsetup open --type luks /dev/sdb2 thequiz Enter passphrase for /dev/sdb2: # dmsetup table swanhome: 0 372082688 crypt aes-xts-plain64 0000000000000000000000000000000000000000000000000000000000000000 0 8:8 4096 thequiz: 0 651106305 crypt aes-xts-plain64 0000000000000000000000000000000000000000000000000000000000000000 0 8:18 65535 # The number of sectors 651106305 matches the filesystem size, and 8:18 matches /run/udev/data/b8:18, but I don't know the significance of 65535. Should I recreate the partition, container, or filesystem, and what extra data would I supply to improve things? (The FAT32 filesystem is currently empty.) I can't see numbers here that indicate misalignment. Cheers, David.
