We have a bunch of variables in the default environment that used to be important for compatibility with old Vyatta scripts or early VyOS re-implementations of them, but aren't used anywhere anymore and just makes it harder to reason about the variables we actually need.
Among them:
* `vyos_cfg_templates`
* `vyatta_prefix`
* `vyatta_htmldir`
* `vyatta_datadir`
* `vyatta_bindir`
* `vyos_libdir`
* `vyatta_localstatedir`
* `vyos_op_templates`
* `vyos_cfg_templates`
* `vyatta_libexecdir`
* `vyatta_prefix`
* `vyos_prefix`
* `vyos_datarootdir`
* `vyatta_sharedstatedir`
* `vyatta_infodir`
* `vyatta_localedir`
* `vyos_sbin_dir`
* `vyos_share_dir`
* `vyos_configdir` — scripts that do use a variable for the config dir, use `$vyatta_sysconfdir`, funnily enough.
For the record, the following variables //are// used:
* `vyatta_sysconfdir` — used in `vyos-router` and in `vyos-boot-config-loader.py`; we could replace it with a more modern name.
* `vyatta_sbindir` — used only in `vyos-router` (its usage there is dubious and likely useless now) and in `vyatta-cfg-cmd-wrapper` (could be hardcoded there)