I though about something like that. It's a trade-off between duplication hassle (bear by me) vs. hassle for the user during the first boot. I'm already some squashfs so it's a little bit the same point. Thanks for the suggestion, Grégoire On Sat, 2009-06-20 at 09:00 +0100, Alex Bligh wrote: > > --On 19 June 2009 16:42:54 -0700 Gregoire Gentil <gregoire@xxxxxxxxxx> > wrote: > > > I need to duplicate a huge number of identical 8GB SD cards on which I > > have 1GB of data at the beginning of the disk on various partitions and > > then a 7GB ext3 partition which is rather empty (just a few MB of data). > > > > The duplicator device enables me to select which sectors I can > > binary-duplicate. I would love to divide by 8 my duplication time, by > > duplicating only the first GB and then the beginning of the 7GB ext3 > > partition. > > I am guessing here about your application, but how about: > > 1. Leave the 7GB partition unformatted in the SD card image, set the > partition type in the partition table to a magic value > 2. Make a gzip'd version of a disk image of that partition. Do this by > using a loopback file system on a file the size of the partition > which is initially full of a single magic byte/word. The resultant > file should be tiny as the image will be mostly blocks full of the > magic byte/word. Put this on another partition. > 3. In the boot code for the device (I am assuming you can change that > or better still it is on the CF device), put a little bit of code > that > a) checks the partition table for the magic number, and if set, > do this: > b) mounts the partition with the gzip image, extracts it, > writes it (only writing blocks that are not full of the magic > byte/word, so the process will be quick) to the new partition, > then unmounts the partition with the gzip image so the boot > process can continue > c) change the partition table entry to ext3 > d) continue the boot process > Of course this only happens on the first boot, and is only writing > a few Mb of data. > 4. Only duplicate the first 1GB of the disk > > The program described is a few tens of lines of C linked with zlib. > It also gives you a relatively easy way to restore the partition > if you should ever need to (change partition table magic number back, > reboot). If this is the only r/w partition, that might be useful. > _______________________________________________ Ext3-users mailing list Ext3-users@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/ext3-users
