pve-manager error after apt-get upgrade

Had the same issue I believe, as I also just did a apt-get upgrade, seem to remember it was a perl compilation error in pve-daemon due to a missing new libhttp*perl* package which didn't get added before I did apt-get dist-upgrade...
 
ok but why would it remount root as read only? this makes no sense to me
 
ahh ok, yes this can happen if you use apt-get upgrade, which you should not use, always apt-get dist-upgrade
 
Hm well reason we always first do upgrade before dist-upgrade is that we've experienced several times over time that a node would get a NMI fired as SW watchdog sometimes was held down for longer than 60 sec by some package patching taking too long time, like grub probing our iSCSI luns/LVMs on iSCSI. Hence we've postponed kernel and thus grub patching to a dist-upgrade after most other package patching has been performed in an regular upgrade. Even as suggested w/dpkg --purge os-prober, grub patching is still is too slow ImHO.