Ephemeral w/o FS gets added to fstab

[Nate House]

Using a DS that includes ec2 metadata with an ephemeral disk, even if the ephemeral disk is not formatted with a filesystem, cc_mounts adds an fstab entry that is likely invalid and potentially breaking reboot in some cases. I've seen this affect Debian based images and if needing to reproduce, Rax OnMetal I/O flavor is a good candidate. We are adjusting the base images cloud config to avoid hitting this but, any other cloud providers that provision non-formatted ephemeral disks would likely have similar issues.

[Nate House (nhouse)]

Here is some relevant log data and shows mounts attempting to mount the block dev instead of a valid partition:

Nov 3 21:53:25 debian [CLOUDINIT] openstack.py[DEBUG]: Mapped ephemeral0 to device /dev/sdb
Nov 3 21:53:25 debian [CLOUDINIT] cc_mounts.py[DEBUG]: Mapped metadata name ephemeral0 to /dev/sdb
Nov 3 21:53:25 debian [CLOUDINIT] cc_mounts.py[DEBUG]: changed default device ephemeral0 => /dev/sdb
Nov 3 21:53:25 debian [CLOUDINIT] util.py[DEBUG]: Activating mounts via 'mount -a' failed#012Traceback (most recent call last):#012 File "/usr/lib/python3/dist-packages/cloudinit/config/cc_mounts.py", line 366, in handle#012 util.subp(("mount", "-a"))#012 File "/usr/lib/python3/dist-packages/cloudinit/util.py", line 1687, in subp#012 cmd=args)#012cloudinit.util.ProcessExecutionError: Unexpected error while running command.#012Command: ('mount', '-a')#012Exit code: 32#012Reason: -#012Stdout: ''#012Stderr: 'mount: /dev/sdb is write-protected, mounting read-only\nmount: wrong fs type, bad option, bad superblock on /dev/sdb,\n missing codepage or helper program, or other error\n\n In some cases useful info is found in syslog - try\n dmesg | tail or so.\n'

[James Falcon (falcojr)]

Tracked in Github Issues as https://github.com/canonical/cloud-init/issues/2594