Comment 7 for bug 1634678

## setup
$ git clone git://git.launchpad.net/~smoser/cloud-init/+git/sru-info
$ ./sru-info/bin/enable-proposed
$ ( sudo apt-get -q update && sudo apt-get install -qy cloud-init ) </dev/null
$ dpkg-query --show cloud-init
$ sudo ./sru-info/bugs/lp-1634678/disk-setup
$ sudo ./sru-info/bin/do-reboot clean save=orig

## ssh back in
$ grep cc_disk_setup.py /var/log/cloud-init.log
2017-04-17 14:43:48,488 - stages.py[DEBUG]: Running module disk_setup (<module 'cloudinit.config.cc_disk_setup' from '/usr/lib/python3/dist-packages/cloudinit/config/cc_disk_setup.py'>) with frequency once-per-instance
2017-04-17 14:43:48,491 - cc_disk_setup.py[DEBUG]: setting up filesystems: [{'partition': 'auto', 'label': 'mydata', 'device': '/dev/vdb', 'filesystem': 'ext4'}]
2017-04-17 14:43:48,521 - cc_disk_setup.py[DEBUG]: Creating new filesystem.
2017-04-17 14:43:48,522 - cc_disk_setup.py[DEBUG]: Checking /dev/vdb against default devices
2017-04-17 14:43:48,522 - cc_disk_setup.py[DEBUG]: Identifying device to create mydata filesytem on
2017-04-17 14:43:48,536 - cc_disk_setup.py[DEBUG]: Automatic device for /dev/vdb identified as /dev/vdb1
2017-04-17 14:43:48,536 - cc_disk_setup.py[DEBUG]: File system type 'ext4' with label 'mydata' will be created on /dev/vdb1
2017-04-17 14:43:48,542 - cc_disk_setup.py[DEBUG]: Creating file system mydata on /dev/vdb1
2017-04-17 14:43:48,542 - cc_disk_setup.py[DEBUG]: Using cmd: /sbin/mkfs.ext4 /dev/vdb1 -L mydata

$ grep /mnt /proc/mounts
/dev/vdb1 /mnt ext4 rw,relatime,data=ordered 0 0
$ sudo blkid /dev/vdb1
/dev/vdb1: LABEL="mydata" UUID="3f2d4ff8-2863-4842-b4ec-e54fc3de9a2f" TYPE="ext4" PARTUUID="9ebe6f52-30c4-4523-b771-e6857edbbd65"
$ echo $(date -R) hi mom | sudo tee -a /mnt/my-important-data.txt
Mon, 17 Apr 2017 14:45:27 +0000 hi mom
$ sudo ./sru-info/bin/do-reboot clean save=orig2

## one more time.
## we did not format this time.
$ grep cc_disk_setup.py /var/log/cloud-init.log
2017-04-17 14:46:22,927 - stages.py[DEBUG]: Running module disk_setup (<module 'cloudinit.config.cc_disk_setup' from '/usr/lib/python3/dist-packages/cloudinit/config/cc_disk_setup.py'>) with frequency once-per-instance
2017-04-17 14:46:22,929 - cc_disk_setup.py[DEBUG]: setting up filesystems: [{'filesystem': 'ext4', 'partition': 'auto', 'label': 'mydata', 'device': '/dev/vdb'}]
2017-04-17 14:46:22,948 - cc_disk_setup.py[DEBUG]: Creating new filesystem.
2017-04-17 14:46:22,949 - cc_disk_setup.py[DEBUG]: Checking /dev/vdb against default devices
2017-04-17 14:46:22,949 - cc_disk_setup.py[DEBUG]: Identifying device to create mydata filesytem on
2017-04-17 14:46:22,964 - cc_disk_setup.py[DEBUG]: Automatic device for /dev/vdb identified as /dev/vdb1
2017-04-17 14:46:22,964 - cc_disk_setup.py[DEBUG]: Found filesystem match, skipping formating.

$ cat /mnt/my-important-data.txt
Mon, 17 Apr 2017 14:45:27 +0000 hi mom