Reducing NVRAM usage

[YasharF]

I am running into issues with NVRAM usage on RT-N16 (currently running John's fork, but I think this is a generic issue), and trying to figure out how we can free up more space. The device has a 32K nvram, and my current nvram usage is 29853 bytes (2915 left). I have two devices at two locations, and during the last year I had to do factory setting resets more than two times because while changing settings the router went belly up, probably because of running over the 32k nvram limit.

I have already, added the ddwrt wiki nvram cleanup hack, by adding

for line in `nvram show  | grep =$ `; do var=${line%*=}; nvram unset $var; done

to scripts/init-start

Questions:
I know there are features that I never intend to use on these devices such as the IPv6, RADIUS, Dual WAN, or on-router VPN server or clients including PPTP. Can I reduce the nvram usage by removing the related settings from the nvram?

I have seen quite a few settings when checking with

nvram show | grep ipv6
nvram show | grep radius
nvram show | grep vpn
nvram show | grep pptp

So my thought was to go over the list of variables and then use nvram unset to remove the non-applicable ones, however I noticed that the unsetting does not persist when rebooting. I suspect that just adding unset statements to init-start script may not be sufficient to stop the occasional soft-bricks. What are your thoughts? Do you have any suggestions?

 

[YasharF]

By the way,

for line in `nvram show  | grep =$ `; do var=${line%*=}; nvram unset $var; done

doesn't seem to be working in either init-start, firewall-start, services-start, or even post-mount. Any suggestions on how to run it effectively during startup?