mounting the root fs writable



  • Every now and then someone who is tweaking his phone, advises to re-mount the root fs writable for a short time (to change something there, install add-ons, ..). In the times of Canonical they gave the strict advice not to do so because it could make fail the OTA updates later.

    Is anybody here in the position and knowledge to explain a bit, based on the structure of the OTA file distribution, what exactly could cause problems and what exactly should be avoided or not touched this way? Thanks in advance.



  • I have the same question and concern. I want to remount writeable so I can properly edit stuff in /etc (especially the hosts file to do blocking). On the other hand, I do not want to loose the ability to do future OTA updates...

    This is on the webs http://www.mibqyyo.com/en-articles/2015/11/13/ubuntu-touch-system-rw-bq-canonical-smartphones/ and it's quite detailed, but old. Has anyone here gone though this process, including remounting read-only and do an OTA update?

    Any info / experience is welcome, TIA!



  • My experience.

    I had bqE5 with UT. Remounted to writable, installed git, vim (DON'T do apt-get upgrade, JUST update & install), remounted to read only (frankly, I didn't bother to remount back, just restarted the phone). After everything worked, I was able to install further OTA updates.



  • thanks Jezek. I just did mount writable, edit /etc/hosts, mount read-only without any issues. Now wait for a new OTA :)



  • All these "it worked for me for now" type messages do not lead to any secure information. Want an example based on the change of the file /etc/hosts? The next OWA will just work fine (because it does not care or update the /etc/hosts file). But some OWA in the future wants to update /etc/hosts and checks before the md5 hash of the file because its unmodified hash value is known. And stops now because the md5 hash is not the same any more.

    This is only a guessed example. Without deep knowledge and information about the OWA update process, all is wild guessing.


  • Community

    Basically, your changes will be clobbered. The update system will unconditionally overwrite whatever is currently on the system with its changed version.

    I've never heard of remounting rw breaking the update process.



  • @unisuperbox said in mounting the root fs writable:

    Basically, your changes will be clobbered. The update system will unconditionally overwrite whatever is currently on the system with its changed version.

    I've never heard of remounting rw breaking the update process.

    How is this "overwrite" done? Some kind of tar-archive unpacked or a tree and copied over the existing tree or some kind of to be installed click-packages, or ...?

    Thanks.



  • @guru Agreed. I did save the original hosts file so it would be easy to restore the file and set the filesystem to read-only before doing an OTA. But that too isn't a guarantee, I realise it's a bit of a gamble.


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