Freeze SO Linux, it's possible?
loic.grenie at gmail.com
Thu Dec 11 16:57:01 UTC 2008
2008/12/11 Bart Silverstrim <bsilver at chrononomicon.com>:
> Loïc Grenié wrote:
>> I'm proposing (and myself using) something in between. I use a live CD
>> that is physically stored on an USB key.
>> There is a read-only filesystem stored on the USB key.
>> There is a read-write filesystem that can be stored in memory or on disk
>> or whatever.
>> Both partition are unioned with aufs (earlier it was unionfs). The resulting
>> partition is read-write, but nothing can occur to the read-only partition
>> (precisely because it is read-only). All modification you make to the
>> unioned partition (including file deletion) are stored on the read-write
>> partition. After eah session you can either choose to just throw away the
>> read-write partition (that's the way the live CD works) or keep it (if it is
>> stored on some kind of disk -- in which case you have a system very
>> similar to a usual one) or use the unioned partition to recreate a new
>> "read-only" partition (if you want to do an upgrade, update, installation
>> of software). This is "Live CD" but with the default system upgradeable
>> and stored on any medium (regular hard drive, CD, USB key, external
>> drive). I suspect it would fly on a regular disk (on the key it's a bit slow).
>> As far as I can tell it is very similar to Deep Freeze but it is probably a
>> bit more difficult to use:
> Definitely more convoluted in theory but once set up sounds workable in
> practice, as you know since you're doing it :-)
>>I need to manually recreate the snapshot whe
>> I upgrade the system. When I've configured my USB key (~1.5 years ago,
>> it was with Feisty Fawn) I had to slightly modify the files of the initial
>> ramdisk because I did not really needed the exact same features of
>> Ubuntu Live CD; I don't know if the current initrd of Ubuntu is usable
> Deep freeze is still easier to implement than what you're using since
> you had to do some modification (and DF is near native speed from what I
> can tell, whereas you already acknowledged slower performance.
I have slower performance because I'm using an USB key (program loading,
data writing is all done on my USB key and it's slow). If you use a hard-disk
for the read-only partition and memory for read-write, it's probably roughly
the same speed as a regular linux (memory fills while you use the system,
so it might become slow after a while, especially if you download
If you use a disk partition for both partitions it's probably the
same speed as
a regular Linux (maybe slightly slower on slow processors) -- in that case the
read-write partition must be reformated at each boot, though.
> DF is also a little more transparent since you're keeping in mind what
> is RW and what is RO despite being unioned, no?
Only when you create the setup or when you want to update/upgrade
it. At regular run-time, you don't need to know. The system boots like
any Linux system, except that changes don't survive reboot.
> In other words this might not be an ideal setup for an average end user...?
This is definitely not an ideal setup for an average end user, but Deep
Freeze on Linux is not a very useful program for the average end user. It's
doable for a motivated system administrator (or hacker, in the positive
sense). After the initial setup, which was a pain for me (but I know it's
easier now, but I don't know how much easier) it's not difficult to use,
even when you want to update the "read-only" part.
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