Sorry to be dense, but I couldn't quite figure out how to do that. My
first stumbling block is that /dev/ubd1 and /dev/ubd2 don't exist.
Indeed, there are no ubd* devices at all.. the kernel boot show this:
# sudo -u uml vmlinux \
ubd0=dubya-dev.breezy.rootfs \
ubd1=dubya-dev.cow,breezy.rootfs.pristine \
ubd2=dubya-dev.breezy.rootfs.bak \
con=null con0=null,fd:2 con1=fd:0,fd:1 \
eth0=tuntap,tap0 mem=512M
...
ubda: unknown partition table
Creating "dubya-dev.cow" as COW file for "breezy.rootfs.pristine"
ubdb: unknown partition table
ubdc: unknown partition table
...
* udev requires hotplug support, not started.
But everything on the new server instance works fine. Thinking it was a
udev error, I tried apt-getting udev and hotplug, but as I expected
they're installed and upgraded to the newest versions. A kernel
compilation misconfiguration?
However, even if I were to get that working, I'm not quite sure how to
"compare block by block (512-byte blocks) the two files. replace the
ubd1 block with ubd2 one when they don't match." Something using cmp and dd?
Thanks for the advice.
-Ian
Blaisorblade wrote:
On Friday 16 December 2005 15:47, Ian Smith-Heisters wrote:
Hi all,
I just read about COW, and wish I'd known about them when I first setup
my servers. Now I have several UML rootfs based off of a single original
rootfs, which I mirrored just by copying. Is there any way I can
retroactively create a COW from the modified rootfs and the original
rootfs? Sort of like doing a diff? Can uml_mkcow do this?
Thanks,
Ian
There's no such tool currently - however it can be coded in a relatively easy
way inside Uml.
ubd0=another_root_fs ubd1=new_cow_file,orig_one ubd2=modified_one
open /dev/ubd1
open /dev/ubd2
compare block by block (512-byte blocks) the two files
replace the ubd1 block with ubd2 one when they don't match.
finally, ubd1 will match ubd2 but on ubd1 the changes have been made on the
COW file.
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