ubuntu-device-flash should not create data in writable partition

[Oliver Grawert]

after a fresh image creation the directory /system-data/var/lib/cloud/seed/nocloud-net/ with two files (meta-data, user-data) has been created in the writable partition.

having pre-created data in that partition makes us very inflexible for just booting from a freshly formatted empty media (with the proper writable label) or for booting with the writable partition in a tmpfs for readonly non-persistent installations.

the writable partition should not contain data before first boot. if needed, such files should be copied in place with an initramfs hook during boot from a storage space in the /boot partition.

without these files in place the system does not boot properly (i.e. when formatting the writable partition to do a "factory reset"). cloud-init hangs forever with error messages like http://paste.ubuntu.com/12096282/ printed to console in a loop.

[Ricardo Salveti (rsalveti)]

The only issue about storing such files at /boot is that we usually want to avoid touching such partition, for various reasons (and it's also vfat). But we should indeed not rely on the writable partition.

I know this is used by the cloud images, and MAAS was also going to use the same mechanism, so we need to align the fix with everyone when landing it.

[Leo Arias (elopio)]

The new path is /var/lib/cloud/seed/nocloud-net/

[Oliver Grawert (ogra)]

irrelevant with all-snaps since everything ends up in the writable partition now