I use this command to mount a tmpfs filesystem on top of `/usr` using
OverlayFS to temporarily make the FMOS immutable filesystem mutable.
This is particularly useful for testing changes without rebuilding the
image.
The GNU readline library also has a vi editing mode, but as it is
initialized at application start up, the only way to configure it is to
write a configuration file. The library will read from `~/.inputrc` by
default, but this can be overridden using the `INPUTRC` environment
variable.
