Disable DAHDi Configuration Writes

Hello all ----

Could someone explain me what is the advadvantage to disable the Disable DAHDi Configuration Writes under Advanced Settings in FreePBX distro ?

Look forward to your reply.


If you have DAHDI working through a configuration that does not interact with FreePBX (you’ve developed your own system for managing your DAHDI config, for example), turning off configuration writes would be a good thing. You can still see what’s going on in DAHDI, you just choose to not let FreePBX modify it and possibly change it in a way that breaks your hand-crafted config.


Okay, i got a digital card and an analog card in my freepbx, the digital card was configure in CLI for set up the E1 mode, at each reboot the cards lost config and i must to re configure the cards… if i turning this feature it will fix this issue ? It’s that you mean ???

Look forward to your reply.

Thanks !


I turn this feature off when the defaults in FreePBX’s DAHDI configuration and my DAHDI configuration don’t reconcile.

An example would be echo cancellation. DAHDI in FreePBX can set the echo cancellation for the individual channels on my DAHDI card, but it sets it wrong (until I change it in the Advanced Settings). So, until I get that updated, I turn off the FreePBX updates.

Getting the configuration of a DAHDI card right can be a very “artistic” endeavor, so letting a tool like FreePBX (which is a "get it right 90% of the time thing for DAHDI) handle the configuration of your DAHDI card channels may not be the best choice. Also, while the Sangoma cards might be the most common, they are not the only cards out there, and not every option for every other card is covered.

Now, if you turn the machine off and have to reconfigure your cards when you turn it back on, I doubt that the FreePBX configuration changes are making much of a difference. It actually sounds to me like your example is a case where the config file is simply not getting processed by the card.

Or maybe, do you think it’s on the card it self, damage???

I am using both digital an analog cards from Diguim.

The thing is i have set them one by one , the analog card keep config after a reboot whereas the digital card not, i must tell you the digital card always set for E1 mode by editing the /etc/modprobe… file,
and all the rest are set in the UI as well as the analog card.

Please let me know your thoughts.

Thansks !

When you make DAHDI changes, all of the managed card config files are modified. So, once you get the files set, you should probably turn off the “write DAHDI config” file option so that the config files don’t get overwritten on an update. If you need to modify anything after that, it needs to be done by hand.

With DAHDI in particular, once the config is set and working, you should never have to change anything in the DAHDI config. There is nothing in FreePBX that should be “unconfiguring” your cards. I’m a believer in getting the DAHDI subsystem (which technically exists outside of both FreePBX and Asterisk) working on it’s own and simply referring Asterisk to it.

The fact that you are using DAHDI options in FreePBX to reset your card configs every time you restart your system tells me that there’s something wrong with your configuration. You shouldn’t have to reset anything every time you start the system up.

Okay, as this is a new card which not has a jumper to switch from T1 to E1 i am follow these steps, please see below : http://kb.digium.com/articles/Configuration/Changing-line-mode-to-T1-or-E1

I waiting to your suggestion.

Thanks !

You should set up the dahdi.conf file once using FreePBX and then Disable Configuration Writes.

Stop Asterisk and Stop Dahdi.

After that, you need to go into the file and hand-update your dahdi.conf file to include these options.

Restart Dahdi.

Restart Asterisk.

Your card is in that class of cards I was talking about - you need to hand-massage the file for it to work with DAHDI (which, remember, is separate from Asterisk) so making the changes in the file once and not allowing the file to be overwritten is the right way to accomplish your goal.

My apologies …[quote=“cynjut, post:8, topic:34133”]
you need to go into the file and hand-update your dahdi.conf file

I am sorry, i am not totally clear of what you said… It’s a cmd i need to type right here or…
Please could you give me an example.

Thanks !


Thanks !

@dicko,i ve proceded that way, i am asking to get an explaination of what @cynjut said.

Thanks !

Just adjust


and disable the dahdi helper after it works.

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Thanks !

I am wondering if i can still editing these files after doing that ?

Thanks !

Of course, as was said Dahdi is a channel driver software independent of FreePBX or Asterisk directly.

Ok, that is a good thing if i still can use it for futher config after doing that.

Thanks !