ERROR: Could not connect to lockdownd: Invalid HostID (-21)

[jhihn]

This error appears when a host which has previously been trusted by the device has had its trust reset (Settings: General: Reset: Reset Location & Privacy) and is plugged in again.

The work-around is to delete the existing trust file in the lockdown directory and re-pair.

It would be nice if this could happen automatically.

[mexmer]

you can manually call unpair

[shaun-mills]

Seeing this too and confirmed that deleting the existing trust file in the lockdown directory does force the the re-paring / trust process to work again.

[jhihn]

You don't have ti nuke it from orbit, you can unpair it, or delete the trust file.
I would like the message changed though (though happy to have a text error string!)
"Invalid HostID" isn't a good description. The HostID is valid, the error is in the relationship.

[shaun-mills]

@jhihn can you point me to the function that does the unpair action? Or an example of how you would invoke it

[jhihn]

idevicepair is a binary: implemented here:
https://github.com/libimobiledevice/libimobiledevice/blob/master/tools/idevicepair.c

[lmamane]

I had this issue; I don't remember ever resetting the trust. I didn't even have to unpair, calling "idevicepair pair" worked.

[rootkittt]

where can i find the trust file?

[mailinglists35]

you don't have to delete any file.
just run
idevicepair pair
and that's all

[ryanjkemper]

Ran into the issue today and can confirm running idevicepair pair does resolve this issue when it occurred for me.

I see the security advantage of keeping the current functionality and forcing a re-pair. I am building re-try logic into my script that utilizes this library for backups. I do like @RJVB's idea to at least improve the error message by suggesting to re-pair the device.