lash - 2019-07-18

Am trying to follow the recipe for creating a hidden volume, but can't create the filesystem.

I understand the warning that for inexperienced users it's "nearly impossible" to get the sizing of the volumes right. However, I can't see any description anywhere of what is concealed behind this near impossibility.

At the least, I would have expected an attempt to create an fs with size considerably smaller than the presumably allocated size to succeed. My feeble attempt follows below. Any pointers would be appreciated:

$ veracrypt -t --version
VeraCrypt 1.23
$ veracrypt -t -h
[...]
When using the text user interface, the following procedure must be
 followed to create a hidden volume:
  1) Create an outer volume with no filesystem.
  2) Create a hidden volume within the outer volume.
  3) Mount the outer volume using hidden volume protection.
  4) Create a filesystem on the virtual device of the outer volume.
  5) Mount the new filesystem and fill it with data.
  6) Dismount the outer volume.
  If at any step the hidden volume protection is triggered, start again from 1).
[...]
$ veracrypt -t -c --encryption=Twofish --hash=SHA-512 --random-source=/dev/urandom --volume-type=normal --size=100M --filesystem=none vera.bin
$ veracrypt -t -c --encryption=Twofish --hash=SHA-512 --random-source=/dev/urandom --volume-type=hidden --size=50M --filesystem=none vera.bin
$ veracrypt -t --protect-hidden=yes --filesystem=none vera.bin
$ mkfs.ext4 -b 1024 /tmp/.veracrypt_aux_mnt1/volume 51200
mke2fs 1.45.2 (27-May-2019)
Warning: could not erase sector 2: Operation not permitted
Creating filesystem with 51200 1k blocks and 12824 inodes
Filesystem UUID: b546cba0-65a5-4fe2-b25f-9646eb83f8a8
Superblock backups stored on blocks: 
    8193, 24577, 40961

Allocating group tables: done                            
Warning: could not erase sector 0: Operation not permitted
mkfs.ext4: Operation not permitted while zeroing block 51136 at end of filesystem
Writing inode tables: done                            
ext2fs_update_bb_inode: Inode checksum does not match inode while setting bad block inode
$ mkfs.ext4 -b 1024 /tmp/.veracrypt_aux_mnt1/volume 5120
mke2fs 1.45.2 (27-May-2019)
Warning: could not erase sector 2: Operation not permitted
Creating filesystem with 5120 1k blocks and 1280 inodes

Allocating group tables: done                            
Warning: could not erase sector 0: Operation not permitted
mkfs.ext4: Operation not permitted while zeroing block 5056 at end of filesystem
Writing inode tables: done                            
ext2fs_update_bb_inode: Inode checksum does not match inode while setting bad block inode