Appendix C. Whole Disk Images

Creating a whole disk image from the overcloud-full.qcow2 flat partition image involves the following steps:

$ sudo yum install -y guestfish

Once installed, run the guestfish interactive shell:

$ guestfish

Welcome to guestfish, the guest filesystem shell for
editing virtual machine filesystems and disk images.

Type: 'help' for help on commands
      'man' to read the manual
      'quit' to quit the shell

><fs>

For more information on using guestfish see "The Guestfish Shell" in the Virtualization Deployment and Administration Guide for Red Hat Enterprise Linux 7.

The following Python script uses the guestfish library to automatically generate the whole disk image.

#!/usr/bin/env python
import guestfs
import os

# remove old generated drive
try:
  os.unlink("/home/stack/images/overcloud-full-partitioned.qcow2")
except:
  pass

g = guestfs.GuestFS(python_return_dict=True)

# import old and new images
print("Creating new repartitioned image")
g.add_drive_opts("/home/stack/images/overcloud-full.qcow2", format="qcow2", readonly=1)
g.disk_create("/home/stack/images/overcloud-full-partitioned.qcow2", "qcow2", 10.2 * 1024 * 1024 * 1024) #10.2G
g.add_drive_opts("/home/stack/images/overcloud-full-partitioned.qcow2", format="qcow2", readonly=0)
g.launch()

# create the partitions for new image
print("Creating the initial partitions")
g.part_init("/dev/sdb", "mbr")
g.part_add("/dev/sdb", "primary", 2048, 616448)
g.part_add("/dev/sdb", "primary", 616449, -1)

g.pvcreate("/dev/sdb2")
g.vgcreate("vg", ['/dev/sdb2', ])
g.lvcreate("var", "vg", 5 * 1024)
g.lvcreate("tmp", "vg", 500)
g.lvcreate("swap", "vg", 250)
g.lvcreate("home", "vg", 100)
g.lvcreate("root", "vg", 4 * 1024)
g.part_set_bootable("/dev/sdb", 1, True)

# add filesystems to volumes
print("Adding filesystems")
ids = {}
keys = [ 'var', 'tmp', 'swap', 'home', 'root' ]
volumes = ['/dev/vg/var', '/dev/vg/tmp', '/dev/vg/swap', '/dev/vg/home', '/dev/vg/root']
swap_volume = volumes[2]

count = 0
for volume in volumes:
  if count!=2:
    g.mkfs('ext4', volume)
    ids[keys[count]] = g.vfs_uuid(volume)
  count +=1

# create filesystem on boot and swap
g.mkfs('ext4', '/dev/sdb1')
g.mkswap_opts(volumes[2])
ids['swap'] = g.vfs_uuid(volumes[2])

# mount drives and copy content
print("Start copying content")
g.mkmountpoint('/old')
g.mkmountpoint('/root')
g.mkmountpoint('/boot')
g.mkmountpoint('/home')
g.mkmountpoint('/var')
g.mount('/dev/sda', '/old')

g.mount('/dev/sdb1', '/boot')
g.mount(volumes[4], '/root')
g.mount(volumes[3], '/home')
g.mount(volumes[0], '/var')

# copy content to root
results = g.ls('/old/')
for result in results:
  if result not in ('boot', 'home', 'tmp', 'var'):
    print("Copying %s to root" % result)
    g.cp_a('/old/%s' % result, '/root/')

# copy extra content
folders_to_copy = ['boot', 'home', 'var']
for folder in folders_to_copy:
  results = g.ls('/old/%s/' % folder)
  for result in results:
    print("Copying %s to %s" % (result, folder))
    g.cp_a('/old/%s/%s' % (folder, result),
           '/%s/' % folder)

# create /etc/fstab file
print("Generating fstab content")
fstab_content = """
UUID={boot_id} /boot ext4 defaults 0 2
UUID={root_id} / ext4 defaults 0 1
UUID={swap_id} none swap sw 0 0
UUID={tmp_id} /tmp ext4 defaults 0 2
UUID={home_id} /home ext4 defaults 0 2
UUID={var_id} /var ext4 defaults 0 2
""".format(
  boot_id=g.vfs_uuid('/dev/sdb1'),
  root_id=ids['root'],
  swap_id=ids['swap'],
  tmp_id=ids['tmp'],
  home_id=ids['home'],
  var_id=ids['var'])

g.write('/root/etc/fstab', fstab_content)

# unmount filesystems
g.umount('/root')
g.umount('/boot')
g.umount('/old')
g.umount('/var')

# mount in the right directories to install bootloader
print("Installing bootloader")
g.mount(volumes[4], '/')
g.mkdir('/boot')
g.mkdir('/var')
g.mount('/dev/sdb1', '/boot')
g.mount(volumes[0], '/var')

# do a selinux relabel
g.selinux_relabel('/etc/selinux/targeted/contexts/files/file_contexts', '/', force=True)
g.selinux_relabel('/etc/selinux/targeted/contexts/files/file_contexts', '/var', force=True)

g.sh('grub2-install --target=i386-pc /dev/sdb')
g.sh('grub2-mkconfig -o /boot/grub2/grub.cfg')

# create dracut.conf file
dracut_content = """
add_dracutmodules+="lvm crypt"
"""
g.write('/etc/dracut.conf', dracut_content)

# update initramfs to include lvm and crypt
kernels = g.ls('/lib/modules')
for kernel in kernels:
  print("Updating dracut to include modules in kernel %s" % kernel)
  g.sh('dracut -f /boot/initramfs-%s.img %s --force' % (kernel, kernel))
g.umount('/boot')
g.umount('/var')
g.umount('/')

# close images
print("Finishing image")
g.shutdown()
g.close()

Save this script as a executable file on the undercloud and run it as the stack user:

$ ./whole-disk-image.py

This automatically creates the whole disk image from the flat partition image. Once the whole disk image creation completes, replace the old overcloud-full.qcow2 image:

$ mv ~/images/overcloud-full.qcow2 ~/images/overcloud-full-old.qcow2
$ cp ~/images/overcloud-full-partitioned.qcow2 ~/images/overcloud-full.qcow2

You can now upload the whole disk image along with your other images.

You can also use guestfish to encrypt volumes on your whole disk image. This requires using the luks-format subcommand, which erases the current volume and creates an encrypted volume.

The following Python script opens the overcloud-full-partitioned.qcow2 image created previously, removes the current home volume (which is empty), and replaces it with an encrypted home volume:

#!/usr/bin/env python
import binascii
import guestfs

g = guestfs.GuestFS(python_return_dict=True)
g.add_drive_opts("/home/stack/images/overcloud-full-partitioned.qcow2", format="qcow2", readonly=0)
g.launch()

random_content = binascii.b2a_hex(os.urandom(1024))
g.luks_format('/dev/vg/home', random_content, 0)
g.luks_open('/dev/vg/home', random_content, 'cryptedhome')
g.vgscan()
g.vg_activate_all(True)
g.mkfs('ext4', '/dev/mapper/cryptedhome')
g.mount('/dev/vg/root','/')

volumes = lvs()
volumes.remove('/dev/vg/home')
volumes.remove('/dev/vg/root')
volumes.remove('/dev/vg/swap')
fstab_content = []
fstab_content.append('UUID=%s /boot ext4 defaults 0 2' % g.vfs_uuid('/dev/sda1'))
fstab_content.append('UUID=%s / ext4 defaults 0 1' % g.vfs_uuid('/dev/vg/root'))
fstab_content.append('UUID=%s none swap sw 0 0' % g.vfs_uuid('/dev/vg/swap'))
fstab_content.append('/dev/mapper/cryptedhome /home ext4 defaults 0 1')
for volume in volumes:
  volume_name = volume.replace('/dev/vg/', '')
  fstab_content.append('UUID=%s /%s ext4 defaults 0 2' % (g.vfs_uuid(volume), volume_name))

g.write('/etc/fstab', '\n'.join(fstab_content))
print '\n'.join(fstab_content)

g.write('/root/home_keyfile', random_content)
g.chmod(0400, '/root/home_keyfile')

mapper = """
home UUID={home_id} /root/home_keyfile
""".format(home_id=g.vfs_uuid('/dev/mapper/cryptedhome'))
g.write('/etc/crypttab', mapper)

g.luks_close('/dev/mapper/cryptedhome')
g.selinux_relabel('/etc/selinux/targeted/contexts/files/file_contexts', '/', force=True)
g.shutdown()
g.close()

This script also:

Use this script as an example to create encrypted volumes as part of your whole disk image creation process.

To upload a whole disk image, use the --whole-disk-image option with the image upload command. For example:

$ openstack overcloud image upload --whole-disk --image-path /home/stack/images

This command uploads the images from /home/stack/images but treats the overcloud-full.qcow2 file as a whole disk image. This means you must rename the desired whole disk image to overcloud-full.qcow2 before running the image upload command.