Take a look at
# 66-env -t boot boot@system
## Use udev [yes|no]
## If set to no the following variables has no effects or set to no:
## SETUPCONSOLE, KEYMAP, FONT, FONT_MAP, FONT_UNIMAP, CRYPTTAB, DMRAID,
## BTRFS, LVM
# [...]
## Boot inside a container [yes|no].
## If set to yes the following variables have no effect or are set to no:
## HARDWARECLOCK, SETUPCONSOLE, KEYMAP, FONT, FONT_MAP, FONT_UNIMAP, CRYPTTAB
## SWAP, LVM, DMRAID, BTRFS, ZFS, UDEV, SYSCTL, FORCECHCK, CGROUPS
## MODULE_SYSTEM, RANDOMSEED, MNT_NETFS
# [...]
## Active encrypted devices [yes|no].
CRYPTTAB=!no