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Smartest way to keep (some?) settings when clearing NVRAM

Discussion in 'Tomato Firmware' started by bersbers, Jul 15, 2014.

  1. bersbers

    bersbers Network Newbie Member

    I am quite familiar with linux and somewhat familiar with the nvram shell command. I really appreciate that firmwares are being updated so regularly (such as Shibby's), and clearly, OpenSSL bugs etc. mandate that we regularly apply these updates. However, manually reconfiguring the firmware after each upgrade is a huge pain.
    I understand that backing up the complete NVRAM is not possible (why that is, I am not so sure). However, could it not be possible to backup some of the settings, like Wi-Fi keys, MAC addresses and so on? Is there a list of settings that one can safely export, keep and re-import after upgrading? What would I need to check if I wanted to manually find out which settings I could keep? Should I compare the NVRAM contents of the old and the new firmware versions (after resetting the NVRAM in each), and if an entry matches, would it be safe to copy over this particular setting?

    Some more questions for my understanding:
    - Does the order of entries in the NVRAM matter?
    - Do additional entries in the NVRAM hurt? Let's say I want to use this to send a message to the NSA in case they want my router, could I store an extra entry in the NVRAM with a greeting or would this mess up the other entries?

  2. dc361

    dc361 LI Guru Member

    There is, of course, the built-in backup command that is available through the web interface on the ADMINISTRATION->CONFIGURATION page. Beside that method which captures the entire contents of NVRAM, a number of us use scripts to export key nvram values which we use to reestablish settings after a reset to defaults.

    Addressing your questions..
    Does the order of the entries on the NVRAM matter? -- as far as I know -- no.
    Do additional <snip> ... Not quite as simple. Additional entries would not hurt as long as you do not consume all of the available space but without modifying the firmware, there is not a way to have these entries survive a reset to defaults.
  3. bersbers

    bersbers Network Newbie Member

    Yes, I know that one. Using it to restore the configuration, however, seems very similar to not clearing the NVRAM at all, isn't it? The backup is basically a gzipped text-file version which would allow me to receive the NVRAM settings, but I would still need to select the appropriate settings that I can safely carry iver, which is the main purpose of my previous question :)

    Is any of these script freely available somewhere, ideally (but not necessarily) with a bit of explanation?
  4. Grimson

    Grimson Networkin' Nut Member

  5. Wolfgan

    Wolfgan Reformed Router Member

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