WRTs with dual partitions - does each have its own nvram?

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Rickers
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Joined: 10 May 2015
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PostPosted: Sun Jan 03, 2021 18:44    Post subject: WRTs with dual partitions - does each have its own nvram? Reply with quote
Hi,
I have a WRT1900ACv1. Do these routers have a separates nvram store for each partition or is there one shared nvram?
Regards, Rick
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msoengineer
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Joined: 21 Jan 2017
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Location: Illinois Moderator

PostPosted: Sun Jan 03, 2021 21:59    Post subject: Reply with quote
WRONG: Yes each partition has its own nvram.

Correct: NVRAM is shared between the two partitions, so be very careful in reverting when mappings change...see my next comments for when nvram settings changed...

Edited in Red

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Last edited by msoengineer on Mon Jan 04, 2021 4:49; edited 1 time in total
Rickers
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Joined: 10 May 2015
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PostPosted: Sun Jan 03, 2021 23:40    Post subject: Reply with quote
That's what I expected, but I wanted to ask first.

I spent two hours today experimenting with this. These recent releases are stepping on the nvram in the "other" partition. I tried 44048 in partition 1, with the latest version (45229) in partition 2. Any change to anything on partition 2 and, on booting back into partition 1, I'm prompted to set the admin creds and my settings are all gone.

I can put 44048 in both partition with different settings no problem, changing settings, switching back and forth between partitions, etc. Settings are retained.

-Rick
msoengineer
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Joined: 21 Jan 2017
Posts: 1782
Location: Illinois Moderator

PostPosted: Mon Jan 04, 2021 0:40    Post subject: Reply with quote
The nvram mappings changed between those builds at 44910 and you likely spawned nvram gremlins. Try the new 45229 build and perform a factory reset and reload all your settings.
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FORUM RULES

TIPS/TRICKS: Best QCA Wifi Settings | Latency tricks | QoS Port priority | NEVER USE MU-MIMO |
Why to NOT use MU-MIMO | Max Wifi Pwr by Country | Linux Wifi Pwr | AC MCS & AX MCS | QCA 5Ghz chnls to use | WIFI Freq WIKI | TFTP R7800 | Don't buy AX | IPERF3 How-To

[R9000]52396 nightly (Main Router)
[EA8500]43192 & 45493 (2xOffsite)
[R7800] resting
[WDR3600]BS 44715 (Offsite)
[A7v5]BS 43038 (Offsite+spare napping)
blkt
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Joined: 20 Jan 2019
Posts: 5660

PostPosted: Mon Jan 04, 2021 2:25    Post subject: Reply with quote
Both firmware partitions are separate from each other, but the system configuration space is shared.

So, don't mix up an old build configuration with a new build and vice versa.
SurprisedItWorks
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Joined: 04 Aug 2018
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PostPosted: Mon Jan 04, 2021 4:31    Post subject: Reply with quote
Agree with blkt. nvram is shared. I learned it the hard way, by assuming otherwise and screwing everything up. Eventually I did careful experiments to verify that there is only one, shared, nvram configuration space.
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Rickers
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Joined: 10 May 2015
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PostPosted: Tue Jan 05, 2021 18:06    Post subject: Reply with quote
blkt wrote:
Both firmware partitions are separate from each other, but the system configuration space is shared.

So, don't mix up an old build configuration with a new build and vice versa.
I guess that explains it. Smile
u251
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Joined: 06 Oct 2018
Posts: 30

PostPosted: Tue Jan 05, 2021 19:08    Post subject: Interesting Topic Reply with quote
Is this thinking right then:

1:Flash a new version over an older version

2:Save out a config backup file. When doing so only variables relevant to new version will be saved.

3:Preform a nvram erase and reboot:

4:Reload the newly created config file. This insures no invisible gremlin variables are loaded.

5:Now just page thru all the settings looking for any that did not reload correctly and need to be edited.

"Both firmware partitions are separate from each other, but the system configuration space is shared"

I accept that there is a sharing but there must also be some settings that are saved and are unique to each partition. Right?
blkt
DD-WRT Guru


Joined: 20 Jan 2019
Posts: 5660

PostPosted: Tue Jan 05, 2021 19:29    Post subject: Re: Interesting Topic Reply with quote
u251 wrote:
Is this thinking right then:

1:Flash a new version over an older version

2:Save out a config backup file. When doing so only variables relevant to new version will be saved.

3:Preform a nvram erase and reboot:

4:Reload the newly created config file. This insures no invisible gremlin variables are loaded.

5:Now just page thru all the settings looking for any that did not reload correctly and need to be edited.

No, reset and manually reconfigure then save and reboot. Then, backup for use with the same build only.

u251 wrote:
I accept that there is a sharing but there must also be some settings that are saved and are unique to each partition. Right?

Wrong. It's the same config space. They both read from and write to the same location.
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