This is a simple tool mainly aimed to creating disk image dump that can with careful planning and execution be installed to a live system (with disks mounted read only).

This horrible thing is useful in some low end cloud providers that won't let you choose your OS images freely, but happen to have such image that the user can reboot as read only.

USE THIS THING WITH EXTREME CAUTION. IF YOU DON'T KNOW WHAT YOU ARE DOING, YOU'LL DESTROY YOUR DATA. EVEN IF YOU KNOW, WHAT YOU ARE DOING, YOU CAN DESTROY YOUR DATA. IF YOUR RISING STAR IS NEAR URANUS, YOU CAN DESTROY YOUR DATA.

YOU HAVE BEEN WARNED.

Let's assume, you have a VirtualBox VDI image that has your entire bootable system. Remember to shut down the virtual machine before you start.

$ qemu-img convert -f vdi ../somewhere/my-bootable-disk.vdi -O raw my-bootable-disk.raw

$ create-dump my-bootable-disk.raw my-bootable-disk.dump

$ rm my-bootable-disk.raw

Now that you have a dump file my-bootable-disk.dump let's assume that your cheap cloud server is running in IP address 1.2.3.4 and has been modified so that everything is mounted read only (and where possible unmounted). Remember also to disable swap and lvm writes etc. Disable all possible daemons from the server.

Before you made the server read only, you naturally remembered to copy or compile install-dump binary there. If you didn't, mount a tmpfs partition somewhere and copy install-dump binary there (assuming you have compatible binary at hand). Furthermore, let's assume that your boot disk is /dev/sda.

$ cat my-bootable-disk.dump | gzip | ssh 1.2.3.4 'gunzip - | /wherever/it/is/install-dump -r /dev/sda

At this point, the die has been cast and if the dump installation breaks or system crashes or something, you have most probably killed your cloud server for good and must start over by installing a cloud vendor provided image and setting it read only etc.

Since there is a live filesystem is running, the system may crash and all weird stuff may happen. But if the system really is read-only, the dump should be written and system rebooted.

Timo J. Rinne tri@iki.fi

GPL-2.0