Outmoding CDs (LiveCD)
John Richard Moser
nigelenki at comcast.net
Wed Feb 15 17:57:47 GMT 2006
John Richard Moser wrote:
[...]
> The resulting drive would appear as follows:
>
>
> [VFAT...][SQUASHFS....][root overlay...............][swap...][/boot]
>
> It would be possible also to separate /home from the overlay:
>
> [VFAT...][SQUASHFS....][root overlay.][/home.......][swap...][/boot]
>
[...]
>
> This has the particular advantage that grub can contain an entry that
> loads an initrd with the command line "reset_overlay" to reset the
> system. The result would be that the initrd would load, load modules,
> and read its configuration files to set up {/ <-> OVERLAY}; but then
> instead of setting up the proper overlay on /, it would FORMAT the
> overlay, FORMAT /boot, copy /boot from the squashfs back to /boot,
> correct menu.lst, sync, and reset.
>
> The result of this is that the system can be reset to its initial
> install state in about 15 seconds; however, the /home directory is
> isolated. We may keep a copy of /etc/{passwd,group} (on boot at each
> shutdown or boot up) and parse for all users and groups >1000 <60000
> after the wipe as well, to make sure all user names and passwords are
> re-entered into the system properly. A "Clear Passwords" option could
> clear the passwords, but this has its own security concerns (but anyone
> with physical access can do this anyway).
>
[...]
> The rapid reinstall feature could be tinkered with for base installs as
> a fast backup. It may be possible to squashfs the union of {/ <->
> OVERLAY} at user request and then reboot, destroy the two partitions (if
> they're adjacent) and resize, throw the new squashfs image in, and
> continue loading as normal. This requires, of course, somewhere to PUT
> the new squashfs image in the meanwhile; but it would facilitate a hard
> snapshot of the system that could be instantly restored. Separate / and
> /home are highly recommended in this setting, as /home may contain huge
> things like MP3 files and videos and sensitive documents that you may
> want to shred later.
I should have mentioned also, this entire feature makes LiveCD rescue a
pain in the ass, because you have an unpredictable overlay file system
with a static rootfs. If /home is on /(overlay) in this layout, it may
be difficult for a user to go in with a Live CD and back up their
existing data before reformat.
I also should note that the SquashFS would easily fit the bill as a
LiveCD base, so this could quickly become a "Live Stick" by just
ignoring the overlay and unionfsing with a tmpfs, as with a LiveCD.
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