On Tue 12 Apr 2016 at 17:28:14 (-0400), ken wrote: > On 04/12/2016 03:27 AM, to...@tuxteam.de wrote: > >On Mon, Apr 11, 2016 at 08:31:16PM -0500, David Wright wrote: > >>On Mon 11 Apr 2016 at 19:02:45 (-0400), ken wrote: > >>>This is on Wheezy for a Raspberry Pi. > >>> > >>>Using dd, I copied the SD card for one (nicely working and > >>>configured) system onto another SD card [...]
> It sounds like "update-initramfs -v -u all" should be the last thing > I do before the initial reboot, yes? > > > >Beware that now you have two different file systems with > >the same UUID. This might confuse some all too credulous > >programs that rely on (re-) seeing the same medium if the > >UUID didn't change. > > Very good to know... and I didn't know that at all. A quick look > around found me dbus-uuidgen, a command to create a new uuid. It's > stored in /var/lib/dbus/machine-id says the manpage... and > confirmed. Is that the UUID you're referring to? > > The manpage makes this one seem easy... > > cd [the SD card's / mount point] > dbus-uuidgen > var/lib/dbus/machine-id Not that one, but that's worth doing (assuming that the mount point is not / itself). But you need to remove machine-id first or nothing may happen. > There are also things called UUIDs, or 'labels', for devices and for > partitions and for swap(s). Do I need to do something with them as > well? Yes, what you see when you type $ ls -l /dev/disk/by* Whether they matter depends if you're using them or not (though it's bad form to have duplicates). For unencrypted filesystems, the contents of /etc/fstab will show how you're selecting filesystems to mount. If you created your _partitions_ on the clone independently from the original (ie you dd'd /dev/sdc1 for example), then the partition UUIDs will differ. But if you dd'd the entire card (as /dev/sdc for example), then the partition UUIDs (partuuids) will also be duplicated. In both cases, the filesystem UUIDs will have been duplicated; those are the ones in /dev/disk/by-uuid/ which are used by /etc/fstab if the latter contains lines starting with UUID=. Grub also picks these up when it writes a new /boot/grub/grub.cfg. The same applies to /dev/disk/by-label and LABEL= if you use those. (Grub doesn't.) tune2fs will let you change the UUID and LABEL on ext filesystems. I use gdisk to create partitions, and that handles partition UUIDs (called GUIDs) and disk GUIDs. I think that becomes important with encrypted disks, but others may need to help you there. Cheers, David.
