You can't share a profile between Linux and Windows because some files contain absolute paths. In this case it is likely a problem with pkcs11.txt. You will have to use separate profiles and possibly use Sync.

You can't share a profile between Linux and Windows because.... - so have I been in an alternate reality for the last 12 or so years? Because that is how long I have been sharing this actual profile between Linux & Windows! Or is this some problem that has been introduced in the latest enhancements that Mozilla have decided to foist upon us? If so, then it's pretty poor design.

Two profiles - not a chance. One profile is enough to deal with, with what can only be described as the worst configuration system I've come across, which includes plenty in the last 30 years of IT. Trusting a third party with my bookmarks and passwords, Sync, yeah, that's not going to happen.

Why does pkcs11.txt use absolute paths? What is wrong with using system/environment variables. Mozilla talks about freedom & choice, so how about some platform/OS independence.

     Andrew

The pkcs11.txt file stores data used by the Software Security Device (Password Manager). This device operates independent in its own processor thread for security reasons and uses UDP ports to communicate.

• Options/Preferences -> Privacy & Security
  Certificates : Security Devices

I forgot about compatibility.ini that stores the path of the Firefox version that last used this profile. That will cause Firefox 67 and later to refuse to use the profile across platforms.

You would have to use Bash script on Linux and a Cmd script on Windows to swap the correct pkcs11.txt and compatibility.ini in place.

See also:

• /questions/1260190 Firefox 67 breaks shared profile between Ubuntu and Windows10

So after being away for a bit, I'm now back home and managed to fix this, thanks to the linked question, 1260190, above. The steps are as follows:

1) Create a new profile in Linux - this is a throw-away profile after things are set up and working.

2) Create a new profile in Win10 - this too is a throw-away after things are set up and working.

3) The profile that contains all the goodies, and now can't be accessed due to the new enhancements is in d:\XXX\internet\firefox\myNormalProfile. Create a new dir at the same level, d:\XXX\internet\firefox\platformSpecific. Beneath this, create two more dir's linux & win10.

4) From your new profile under Linux, step 1), copy the files compatibility.ini and pkcs11.txt to the ......platformSpecific\linux dir.

5) From your new profile under Win10, step 2), copy the files compatibility.ini & pkcs11.txt to the ......platformSpecific\win10 dir.

6) I've just realised that the machine I'm doing this on is only used by me hence has only one login, whether it be Linux or win10. If you have multiple logins, you will need to do this for each login.

7) Under Linux edit ~/.bashrc and add the line:

cp /mnt/win10/data/XXX/internet/firefox/platformSpecific/linux/* /mnt/win10/data/XXX/internet/firefox/myNormalProfile

All of the mounting is so that I can see the win10 partitions from Linux. If you are dual booting Linux & win10 and sharing firefox profiles, I'll assume you're smart enough to work out what I'm doing mountwise. The "data" bit in the path is my win10 d drive.

8) Under win10 create a little *.bat file in the ...platformSpecific\win10 dir

       copy compatibility.ini ..\..\myNormalProfile
       copy pkcs11.txt ..\..\myNormalProfile

and then create a link to it in the startup dir for the machine.

9) Now when either of the OS's boot they will copy their respective compatibility.ini & pkcs11.txt files into the profile that contains all of the goodies.

10) Now turf out the two throw-away profiles from 1) & 2)

So this is how I've gotten around this feature. Nice of Mozilla to break about 12 years of easy sharing. A bit of thought could have prevented this problem from happening, but who am I to complain, I only use the software, and have worked as a code monkey for close to 30 years, I'm not some developer with minimal real world experience that has to justify their existence and obviously knows better than me.....