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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