Rebooted after upgrade from 6.12.6, seems services cannot create pid files for lack of space on the device, not sure on which storage they are created, the USB is only 13% used. Of course since nothing starts I guess rolling back will be a pita.
Feb 17 08:46:24 Tower emhttpd: shcmd (35): /etc/rc.d/rc.avahidaemon start
Feb 17 08:46:24 Tower root: Starting Avahi mDNS/DNS-SD Daemon: /usr/sbin/avahi-daemon -D
Feb 17 08:46:24 Tower avahi-daemon[13749]: Found user 'avahi' (UID 61) and group
Adding these lines to the go file seems to be working and no services complaining about dbus:
#increase /run size
/bin/mount -t tmpfs tmpfs /run -o remount,size=64M
#start dbus
/usr/bin/dbus-uuidgen --ensure
/usr/bin/dbus-daemon --system
#start elogind
/etc/rc.d/rc.elogind start
Still don't think this is a great solution, ideally the size of /run should be increased at the first mount before any service starts.