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