<div class="gmail_quote">On Mon, Oct 24, 2011 at 9:02 AM, Mr Dash Four <span dir="ltr"><<a href="mailto:mr.dash.four@googlemail.com">mr.dash.four@googlemail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">
<div class="im"><br>
>> 1. How is the LiveCD file system constructed/built? I've read a variety<br>
>> of articles and it seems that it is close to the UnionFS (rom+ram<br>
>> "partitions"), but I am not sure that is used with the new versions of<br>
>> Linux. I see there are multiple loop mounts on the system, but can't<br>
>> figure out what they are.<br>
>><br>
><br>
> It is originally written into an ext4 image. That image is then compacted<br>
> and then written to a squashfs file system.<br>
><br>
</div>I am aware of all that - squashfs.img is constructed (which encapsulates<br>
the real ext3/4 partition in a separate file - ext4.img I think it was<br>
called), but what I was after is how is this actually mounted on the<br>
live system so that it is "read-write"? From what I can see there are<br>
multiple loop partitions used (in conjunction with dm), but this is as<br>
far as my knowledge goes, unfortunately.<br>
<div class="im"><br>
>> 2. My understanding is that all files that are modified in the "live"<br>
>> image are stored "separately" on a "ram partition". If that is indeed<br>
>> the case, can I look at what has been "modified" during the live<br>
>> session? This is easily visible and implemented in UnionFS by a simple<br>
>> "ls" on the ram (i.e. the read-write) part of the UnionFS, but I am not<br>
>> sure how this is organised on the LiveCD system.<br>
>><br>
><br>
> A dm overlay is used. This can either be ram or separate overlay spaces<br>
> for /home and/or /.<br>
</div>I don't have /home, so just /. Could you tell me how is it actually done<br>
at boot up and how is it made "read-write"? I presume there must be some<br>
sort of space where this information is written - I assume it is the<br>
ram, but I am not 100% sure.<br>
<div class="im"><br>
> I don't think this makes it easy to look at just what's<br>
> changed (in terms of efficiency, not commands). You can use find to find<br>
> files with a recent ctime, but you'd need to check every file.<br>
><br>
</div>I know that, but, as you rightly pointed out, I have to trash the whole<br>
/ partition and even then this won't be a complete solution as I also<br>
need to know the time when the system booted up - it is all a bit<br>
clumsy, there must be a better solution to this.<br>
<div><div></div><div class="h5">--</div></div></blockquote><div><br></div><div>See <a href="http://wiki.sugarlabs.org/go/LiveOS_image" style="background-color: transparent; ">http://wiki.sugarlabs.org/go/LiveOS_image</a><span style="background-color: transparent; "> for a page on these issues.</span></div>
<div><span style="background-color: transparent; "><br></span></div><div><span style="background-color: transparent; "> --Fred</span></div></div>