Comment 3 for bug 1816170

After starting the VMs that were not due to the above error coming from QEMU:

juju-5ad6c1-6-kvm-0: stuck in initramfs
juju-5ad6c1-6-kvm-1: shows a login prompt (juju-5ad6c1-6-kvm-1 login:)
juju-5ad6c1-6-kvm-2: shows a login prompt
juju-5ad6c1-6-kvm-3: stuck in initramfs
juju-5ad6c1-6-kvm-4: shows a login prompt
juju-5ad6c1-6-kvm-5: shows a login prompt

(initramfs) Gave up waiting for root file system device. Common problems:
 - Boot args (cat /proc/cmdline)
   - Check rootdelay= (did the system wait long enough?)
 - Missing modules (cat /proc/modules; ls /dev)
ALERT! LABEL=cloudimg-rootfs does not exist. Dropping to a shell!

(initramfs) cat /proc/cmdline
BOOT_IMAGE=/boot/vmlinuz-4.15.0-46-generic root=LABEL=cloudimg-rootfs ro console=tty1 console=ttyS0

If ./init is ran by hand from the console in this initramfs "Gave up waiting for root file system device" is encountered again.

(initramfs) blkid
/dev/vdb: UUID="2019-03-14-19-44-16-00" LABEL="cidata" TYPE="iso9660"

(initramfs) ls /dev/vd*
/dev/vdb /dev/vda

(initramfs) mount | grep /dev/vd ; echo $?
1

http://manpages.ubuntu.com/manpages/bionic/man8/initramfs-tools.8.html
"If a label is used, as in root=LABEL=rootPart the initrd will search all available devices for a filesystem with the appropriate label, and mount that device as the root filesystem."