Details of the mechanism, introduced after jessie, are in

The rewrite has been complete in the fork for some time, but is on hold pending: (1) consider taking advantage of the functionality in https://github.com/vyos/vyos-1x/blob/current/python/vyos/configsession.py to avoid duplication of code (2) ongoing work on options to replace the python list manipulations in the current rewrite. Regarding the latter point, it was expected that there would be a performance hit in moving away from the legacy C++ backend (via Perl bindings), and the cost was considered worthwhile in order to move forward; one data point is a performance hit of .3 on a 17k line config file, which was not bad, considering.

There is some further discussion here, which I found useful in considering the changes for Stretch:

There is one other use of XorpConfigParser (in the vyatta-config-migrate package), that was not mentioned in the above: the scripts used for persistent interface naming; this is currently being rewritten and reorganized in T1499: 'Move nic to mac mapping out of the configuration file'.

I had initially not planned to drop the explicit set_value for console speed in migrate/system/3-to-4, as this was legacy for the system@4 component definition; however, (1) the file is soon to be removed when we drop config compatibility pre-6.5, (2) it is now redundant/wrong in the /opt/vyatta/etc/config/config.boot, as pointed out by c-po above. I will remove the add_console call from vyatta-config-migrate/migrate/system/3-to-4.

Thanks @c-po --- to clarify, I had pointed out this issue with https://github.com/vyos/vyatta-config-migrate/blob/current/migrate/system/3-to-4 earlier in the task, which will be a non-issue once T805: Drop config compatibility with Vyatta Core older than 6.5 is completed. However, since we are not quite ready for that, I will find a current solution.

https://github.com/jestabro/vyos-1x/tree/load-config

Fix pushed.

Added pull requests:
https://github.com/vyos/vyos-1x/pull/69
https://github.com/vyos/libvyosconfig/pull/2
https://github.com/vyos/vyatta-cfg/pull/18
https://github.com/vyos/vyatta-conntrack/pull/1

Added pull requests:
https://github.com/vyos/vyos-1x/pull/68
https://github.com/vyos/vyatta-cfg/pull/17

Initial commit in fork; support for merging remote files still to be added.
https://github.com/jestabro/vyatta-cfg/commit/96a8f894686b43bbd7f52da8ded87562231cbf52
https://github.com/jestabro/vyos-1x/commit/a31de0d8e2164a6b0bc9a7b6c1e03c053635120b

Testing confirms that the default console speed is set to 115200 when the old migration scripts are removed, as they will be by

Development on this resides in a fork of vyatta-config-migrate (https://github.com/jestabro/vyatta-config-migrate), though properly should reside in a fork of vyos-1x.

Note that the mentioned annoyance of migrate/system/3-to-4 setting the serial console speed should be mooted by 'T805 Drop config compatibility with Vyatta Core older than 6.5'.

To complete this, the corresponding changes need to be made in vyatta-cfg-system; these are straightforward and will be pushed to current. However, there is another mechanism whereby the console speed is explicitly being set to 9600: the vyatta-config-migrate script, called during system initialization, is invoking migrate/system/3-to-4, which sets the console speed; this will require some discussion as to how to best address.