Can you create a file container/volume in LUKS in the same way that you could do with Truecrypt? Otherwise, how can you backup a LUKS partition? Do you have to clone it, for example with dd? or backup each file inside the partition into another encrypted partition? Is there any way of treating the output of luks as a file, for backup purposes?
You can back it up any way you like. Using
dd for backup works of course, but it kind of stinks (regardless of encryption). File based backups are more powerful since it lets you select what to backup, and whether to compress or do it incrementally.
You can LUKS with files,
cryptsetup luksOpen somefile automatically creates a
loop device for you in that case.