Using the boot loader plus an initrd and a kernel with a unionfs like feature compiled it needs to be possible to do the following: * Boot the kernel with the initrd * The initrd will contain an opimimized boot script and any kernel modules needed for the boot media device * The initrd will contain a static busybox with pivot_root * The initrd script will check all the labels on the boot media to find the one that it needs to mount * The initrd script will mount the boot media read-only * The initrd script will pivot to the boot media * The boot media init must account for the fact it was booted read-only and correctly bind mount any part of the file system that needs to be read-write * Alternatively it could re-mount things read-write if it is not an ISOFS
(In reply to comment #0) > correctly bind mount any part of the file system that needs to be > read-write It's really hard to determine which parts of the system need to be 'read-write'. When the user takes a tour in the liveCD distro, every part of the system is possible to be written to, his/her home directory, the /etc/ directory and the /var/ directory. Or maybe the user wants to make a directory under /. So I think maybe we should still use the 'union mount' method. Please see bug#4761 for some additional info.
We should review all packages and recipes and ensure that they do not write to the Read-Only FS, at this point we should not worry about persistent data, so for home directory example it would just be linked to /tmp which is reall /var/tmp and on ramfs. We should find any packages that write into /etc and patch that for the Read-Only FS.
The goal is to make live images workable even if a unionfs like feature is not compiled into kernel. Right? //Chen Qi
Add several bugs to the block list.
merged into poky/master: 2b204500bd20621d29762f23204a000eadc88e00