minor cleanup to ch_openstack_images

removed create, create add together doesn't make sense
removed incomplete sentence

Change-Id: Ic195901b07a358812857bc2b7d542543a0c2fdae
This commit is contained in:
Shilla Saebi 2014-02-17 14:56:56 -05:00
parent 7048c6ffe5
commit cbf9984bc6

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@ -1,4 +1,8 @@
<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE chapter [
<!-- Some useful entities borrowed from HTML -->
<!ENTITY nbsp "&#160;">
]>
<chapter xmlns="http://docbook.org/ns/docbook"
xmlns:xi="http://www.w3.org/2001/XInclude"
xmlns:xlink="http://www.w3.org/1999/xlink" version="5.0"
@ -10,125 +14,131 @@
some of these, the requirement can be fulfilled by installing
the <link
xlink:href="https://cloudinit.readthedocs.org/en/latest/"
>cloud-init</link> package. You should read this section
before creating your own image to be sure that the image
supports the OpenStack features you plan on using.<itemizedlist>
<listitem>
<para>Disk partitions and resize root partition on
boot (cloud-init)</para>
</listitem>
<listitem>
<para>No hard-coded MAC address information</para>
</listitem>
<listitem>
<para>SSH server running</para>
</listitem>
<listitem>
<para>Disable firewall</para>
</listitem>
<listitem>
<para>Access instance using ssh public key
(cloud-init)</para>
</listitem>
<listitem>
<para>Process user data and other metadata
(cloud-init)</para>
</listitem>
<listitem>
<para>Paravirtualized Xen support in Linux kernel (Xen
hypervisor only with Linux kernel version &lt;
3.0)</para>
</listitem>
</itemizedlist></para>
><package>cloud-init</package></link> package. Read
this section before you create your own image to be sure that
the image supports the OpenStack features that you plan on
using.</para>
<itemizedlist>
<listitem>
<para>Disk partitions and resize root partition on boot
(<package>cloud-init</package>)</para>
</listitem>
<listitem>
<para>No hard-coded MAC address information</para>
</listitem>
<listitem>
<para>SSH server running</para>
</listitem>
<listitem>
<para>Disable firewall</para>
</listitem>
<listitem>
<para>Access instance using ssh public key
(<package>cloud-init</package>)</para>
</listitem>
<listitem>
<para>Process user data and other metadata
(<package>cloud-init</package>)</para>
</listitem>
<listitem>
<para>Paravirtualized Xen support in Linux kernel (Xen
hypervisor only with Linux kernel version &lt;
3.0)</para>
</listitem>
</itemizedlist>
<section xml:id="support-resizing">
<title>Disk partitions and resize root partition on boot
(cloud-init)</title>
<para>When you create a new Linux image, the first decision
you will need to make is how to partition the disks. The
choice of partition method can affect the resizing
functionality, as described below.</para>
<para>When you create a Linux image, you must decide how to
partition the disks. The choice of partition method can
affect the resizing functionality, as described in the
following sections.</para>
<para>The size of the disk in a virtual machine image is
determined when you initially create the image. However,
OpenStack lets you launch instances with different size
drives by specifying different flavors. For example, if
your image was created with a 5 GB disk, and you launch an
instance with a flavor of <literal>m1.small</literal>. The
resulting virtual machine instance has, by default,
a primary disk size of 10 GB. When an instance's disk is resized
up, zeros are just added to the end.</para>
<para>Your image needs to be able to resize its partitions on
boot to match the size requested by the user. Otherwise,
after the instance boots, you will need to manually resize
the partitions if you want to access the additional
storage you have access to when the disk size associated
with the flavor exceeds the disk size your image was
created with.</para>
your image was created with a 5&nbsp;GB disk, and you
launch an instance with a flavor of
<literal>m1.small</literal>. The resulting virtual
machine instance has, by default, a primary disk size of
10&nbsp;GB. When the disk for an instance is resized up,
zeros are just added to the end.</para>
<para>Your image must be able to resize its partitions on boot
to match the size requested by the user. Otherwise, after
the instance boots, you must manually resize the
partitions to access the additional storage to which you
have access when the disk size associated with the flavor
exceeds the disk size with which your image was
created.</para>
<simplesect>
<title>Xen: 1 ext3/ext4 partition (no LVM, no /boot, no
swap)</title>
<para>If you are using the OpenStack XenAPI driver, the
Compute service will automatically adjust the
partition and filesystem for your instance on boot.
Automatic resize will occur if the following are all true:<itemizedlist>
<listitem>
<para><literal>auto_disk_config=True</literal>
is set as a property on the image in the
Image Registry.</para>
</listitem>
<listitem>
<para>The disk on the image has only one
partition.</para>
</listitem>
<listitem>
<para>The file system on the one partition is
ext3 or ext4.</para>
</listitem>
</itemizedlist></para>
<para>Therefore, if you are using Xen, we recommend that
when you create your images, you create a single ext3
or ext4 partition (not managed by LVM). Otherwise,
read on.</para>
<para>If you use the OpenStack XenAPI driver, the Compute
service automatically adjusts the partition and file
system for your instance on boot. Automatic resize
occurs if the following conditions are all
true:</para>
<itemizedlist>
<listitem>
<para><literal>auto_disk_config=True</literal> is
set as a property on the image in the image
registry.</para>
</listitem>
<listitem>
<para>The disk on the image has only one
partition.</para>
</listitem>
<listitem>
<para>The file system on the one partition is ext3
or ext4.</para>
</listitem>
</itemizedlist>
<para>Therefore, if you use Xen, we recommend that when
you create your images, you create a single ext3 or
ext4 partition (not managed by LVM). Otherwise, read
on.</para>
</simplesect>
<simplesect>
<title>Non-Xen with cloud-init/cloud-tools: 1 ext3/ext4
<title>Non-Xen with cloud-init/cloud-tools: One ext3/ext4
partition (no LVM, no /boot, no swap)</title>
<para>Your image must be configured to deal with two issues:<itemizedlist>
<listitem>
<para>The image's partition table describes
the original size of the image</para>
</listitem>
<listitem>
<para>The image's filesystem fills the
original size of the image</para>
</listitem>
</itemizedlist></para>
<para>Then, during the boot process:<itemizedlist>
<listitem>
<para>the partition table must be modified to
be made aware of the additional space<itemizedlist>
<listitem>
<para>If you are not using LVM, you
must modify the table to extend the
existing root partition to
encompass this additional
space</para>
</listitem>
<listitem>
<para>If you are using LVM, you can
create add a new LVM entry to the
partition table, create a new LVM
physical volume, add it to the
volume group, and extend the
logical partition with the root
volume</para>
</listitem>
</itemizedlist></para>
</listitem>
<listitem>
<para>the root volume filesystem must be
resized</para>
</listitem>
</itemizedlist></para>
<para>You must configure these items for your
image:</para>
<itemizedlist>
<listitem>
<para>The partition table for the image describes
the original size of the image</para>
</listitem>
<listitem>
<para>The file system for the image fills the
original size of the image</para>
</listitem>
</itemizedlist>
<para>Then, during the boot process, you must:</para>
<itemizedlist>
<listitem>
<para>Modify the partition table to make it aware
of the additional space:</para>
<itemizedlist>
<listitem>
<para>If you do not use LVM, you must
modify the table to extend the
existing root partition to encompass
this additional space.</para>
</listitem>
<listitem>
<para>If you use LVM, you can add a new
LVM entry to the partition table,
create a new LVM physical volume, add
it to the volume group, and extend the
logical partition with the root
volume.</para>
</listitem>
</itemizedlist>
</listitem>
<listitem>
<para>Resize the root volume file system.</para>
</listitem>
</itemizedlist>
<para>The simplest way to support this in your image is to
install the <link
xlink:href="https://launchpad.net/cloud-utils"
@ -136,42 +146,46 @@
<command>growpart</command> tool for extending
partitions), the <link
xlink:href="https://launchpad.net/cloud-initramfs-tools"
>cloud-initramfs-tools</link> package (which will
support resizing root partition on the first boot),
>cloud-initramfs-tools</link> package (which
supports resizing root partition on the first boot),
and the <link
xlink:href="https://launchpad.net/cloud-init"
>cloud-init</link> package into your image. With
these installed, the image will perform the root
partition resize on boot. For example, in the
<filename>/etc/rc.local</filename> file. These
packages are in the Ubuntu and Debian package
repository, as well as the EPEL repository (for
Fedora/RHEL/CentOS/Scientific Linux guests).</para>
<para>If you are not able to install
><package>cloud-init</package></link> package
into your image. With these installed, the image
performs the root partition resize on boot. For
example, in the <filename>/etc/rc.local</filename>
file. These packages are in the Ubuntu and Debian
package repository, as well as the EPEL repository
(for Fedora/RHEL/CentOS/Scientific Linux
guests).</para>
<para>If you cannot install
<literal>cloud-initramfs-tools</literal>, Robert
Plestenjak has a github project called <link
xlink:href="https://github.com/flegmatik/linux-rootfs-resize"
>linux-rootfs-resize</link> that contains scripts
that will update a ramdisk using
<command>growpart</command> so that the image will
resize properly on boot.</para>
<para>If you are able to install the cloud-utils and
cloud-init packages, we recommend that when you create
your images, you create a single ext3 or ext4
partition (not managed by LVM).</para>
that update a ramdisk by using
<command>growpart</command> so that the image
resizes properly on boot.</para>
<para>If you can install the cloud-utils and
<package>cloud-init</package> packages, we
recommend that when you create your images, you create
a single ext3 or ext4 partition (not managed by
LVM).</para>
</simplesect>
<simplesect>
<title>Non-Xen without cloud-init/cloud-tools: LVM</title>
<para>If you cannot install cloud-init and cloud-tools
inside of your guest, and you want to support resize,
you will need to write a script that your image will
run on boot to modify the partition table. In this
case, we recommend using LVM to manage your
partitions. Due to a limitation in the Linux kernel
(as of this writing), you cannot modify a partition
table of a raw disk that has partition currently
mounted, but you can do this for LVM.</para>
<para>Your script will need to do something like the following:<orderedlist>
<title>Non-Xen without
<package>cloud-init</package>/<package>cloud-tools</package>:
LVM</title>
<para>If you cannot install <package>cloud-init</package>
and <package>cloud-tools</package> inside of your
guest, and you want to support resize, you must write
a script that your image runs on boot to modify the
partition table. In this case, we recommend using LVM
to manage your partitions. Due to a limitation in the
Linux kernel (as of this writing), you cannot modify a
partition table of a raw disk that has partitions
currently mounted, but you can do this for LVM.</para>
<para>Your script must do something like the following:<orderedlist>
<listitem>
<para>Detect if any additional space is
available on the disk. For example, parse
@ -210,58 +224,56 @@
/dev/mapper/<replaceable>node-root</replaceable></command>.</para>
</listitem>
</orderedlist></para>
<para>You do not need to have a <filename>/boot</filename>
partition, unless your image is an older Linux
<para>You do not need a <filename>/boot</filename>
partition unless your image is an older Linux
distribution that requires that
<filename>/boot</filename> is not managed by LVM.
You may elect to use a swap per</para>
<filename>/boot</filename> is not managed by LVM.</para>
</simplesect>
</section>
<section xml:id="mac-adddress">
<title>No hard-coded MAC address information</title>
<para>You must remove the network persistence rules in the
image as their presence will result in the network
interface in the instance coming up as an interface other
than eth0. This is because your image has a record of the
MAC address of the network interface card when it was
first installed, and this MAC address will be different
each time the instance boots up. You should alter the
following files:<itemizedlist>
<listitem>
<para>Replace
<filename>/etc/udev/rules.d/70-persistent-net.rules</filename>
with an empty file (contains network
persistence rules, including MAC
address)</para>
</listitem>
<listitem>
<para>Replace
<filename>/lib/udev/rules.d/75-persistent-net-generator.rules</filename>
with an empty file (this generates the file
above)</para>
</listitem>
<listitem>
<para>Remove the HWADDR line from
<filename>/etc/sysconfig/network-scripts/ifcfg-eth0</filename>
on Fedora-based images</para>
</listitem>
</itemizedlist><note>
<para>If you delete the network persistent rules
files, you may get a udev kernel warning at boot
time, which is why we recommend replacing them
with empty files instead.</para>
</note></para>
image because they cause the network interface in the
instance to come up as an interface other than eth0. This
is because your image has a record of the MAC address of
the network interface card when it was first installed,
and this MAC address is different each time that the
instance boots. You should alter the following
files:</para>
<itemizedlist>
<listitem>
<para>Replace
<filename>/etc/udev/rules.d/70-persistent-net.rules</filename>
with an empty file (contains network persistence
rules, including MAC address)</para>
</listitem>
<listitem>
<para>Replace
<filename>/lib/udev/rules.d/75-persistent-net-generator.rules</filename>
with an empty file (this generates the file
above)</para>
</listitem>
<listitem>
<para>Remove the HWADDR line from
<filename>/etc/sysconfig/network-scripts/ifcfg-eth0</filename>
on Fedora-based images</para>
</listitem>
</itemizedlist>
<note>
<para>If you delete the network persistent rules files,
you may get a udev kernel warning at boot time, which
is why we recommend replacing them with empty files
instead.</para>
</note>
</section>
<section xml:id="ensure-ssh-server">
<title>Ensure ssh server runs</title>
<para>You must install an ssh server into the image and ensure
that it starts up on boot, or you will not be able to
connect to your instance using ssh when it boots inside of
OpenStack. This package is typically called
that it starts up on boot, or you cannot connect to your
instance by using ssh when it boots inside of OpenStack.
This package is typically called
<literal>openssh-server</literal>.</para>
</section>
<section xml:id="disable-firewall">
<title>Disable firewall</title>
<para>In general, we recommend that you disable any firewalls
@ -272,7 +284,7 @@
connect to your instance.</para>
</section>
<section xml:id="ssh-public-key">
<title>Access instance using ssh public key
<title>Access instance by using ssh public key
(cloud-init)</title>
<para>The typical way that users access virtual machines
running on OpenStack is to ssh using public key
@ -281,28 +293,32 @@
from the OpenStack metadata service or config drive, at
boot time.</para>
<simplesect>
<title>Use cloud-init to fetch the public key</title>
<para>The cloud-init package will automatically fetch the
public key from the metadata server and place the key
in an account. The account varies by distribution. On
Ubuntu-based virtual machines, the account is called
"ubuntu". On Fedora-based virtual machines, the
account is called "ec2-user".</para>
<title>Use <package>cloud-init</package> to fetch the
public key</title>
<para>The <package>cloud-init</package> package
automatically fetches the public key from the metadata
server and places the key in an account. The account
varies by distribution. On Ubuntu-based virtual
machines, the account is called
<literal>ubuntu</literal>. On Fedora-based virtual
machines, the account is called
<literal>ec2-user</literal>.</para>
<para>You can change the name of the account used by
cloud-init by editing the
<package>cloud-init</package> by editing the
<filename>/etc/cloud/cloud.cfg</filename> file and
adding a line with a different user. For example, to
configure cloud-init to put the key in an account
named <literal>admin</literal>, edit the configuration
file so it has the line:</para>
configure <package>cloud-init</package> to put the key
in an account named <literal>admin</literal>, edit the
configuration file so it has the line:</para>
<programlisting>user: admin</programlisting>
</simplesect>
<simplesect>
<title>Write a custom script to fetch the public
key</title>
<para>If you are unable or unwilling to install cloud-init
inside the guest, you can write a custom script to
fetch the public key and add it to a user account.</para>
<para>If you are unable or unwilling to install
<package>cloud-init</package> inside the guest,
you can write a custom script to fetch the public key
and add it to a user account.</para>
<para>To fetch the ssh public key and add it to the root
account, edit the <filename>/etc/rc.local</filename>
file and add the following lines before the line
@ -357,17 +373,16 @@ done</programlisting>
<section xml:id="metadata">
<title>Process user data and other metadata
(cloud-init)</title>
<para>In addition to the ssh public key, an image may need to
retrieve additional information from OpenStack, such as
<link
<para>In addition to the ssh public key, an image might need
additional information from OpenStack, such as <link
xlink:href="http://docs.openstack.org/user-guide/content/user-data.html"
>user data</link> that the user submitted when
requesting the image. For example, you might want to set the
host name of the instance when it is booted. Or, you might
wish to configure your image so that it executes user data
content as a script on boot.</para>
<para>This information is accessible through the metadata service
or the <link
requesting the image. For example, you might want to set
the host name of the instance when it is booted. Or, you
might wish to configure your image so that it executes
user data content as a script on boot.</para>
<para>This information is accessible through the metadata
service or the <link
xlink:href="http://docs.openstack.org/user-guide/content/config-drive.html"
>config drive</link>. As the OpenStack metadata
service is compatible with version 2009-04-04 of the
@ -378,9 +393,10 @@ done</programlisting>
retrieve user data.</para>
<para>The easiest way to support this type of functionality is
to install the cloud-init package into your image, which
is configured by default to treat user data as an
executable script, and will set the host name.</para>
to install the <package>cloud-init</package> package into
your image, which is configured by default to treat user
data as an executable script, and sets the host
name.</para>
</section>
<section xml:id="write-to-console">
<title>Ensure image writes boot log to console</title>
@ -394,11 +410,12 @@ done</programlisting>
looks something like this:</para>
<programlisting>linux /boot/vmlinuz-3.2.0-49-virtual root=UUID=6d2231e4-0975-4f35-a94f-56738c1a8150 ro console=ttyS0</programlisting>
<para>If <literal>console=ttyS0</literal> does not appear, you
will need to modify your grub configuration. In general,
you should not update the grub.cfg directly, since it is
automatically generated. Instead, you should edit
<filename>/etc/default/grub</filename> and modify the
value of the <literal>GRUB_CMDLINE_LINUX_DEFAULT</literal>
must modify your grub configuration. In general, you
should not update the <filename>grub.cfg</filename>
directly, since it is automatically generated. Instead,
you should edit <filename>/etc/default/grub</filename> and
modify the value of the
<literal>GRUB_CMDLINE_LINUX_DEFAULT</literal>
variable:
<programlisting language="bash">GRUB_CMDLINE_LINUX_DEFAULT="console=ttyS0"</programlisting></para>
<para>Next, update the grub configuration. On Debian-based
@ -417,8 +434,8 @@ done</programlisting>
guests). If you are running the Xen hypervisor with
paravirtualization, and you want to create an image for an
older Linux distribution that has a pre 3.0 kernel, you
will need to ensure that the image boots a kernel that has
been compiled with Xen support.</para>
must ensure that the image boots a kernel that has been
compiled with Xen support.</para>
</section>
<section xml:id="image-cache-management">
<title>Manage the image cache</title>
@ -429,8 +446,8 @@ done</programlisting>
compute nodes share one common
<filename>/var/lib/nova/instances/</filename>
directory.</para>
<para>For information about libvirt images in OpenStack, refer
to <link
<para>For information about libvirt images in OpenStack, see
<link
xlink:href="http://www.pixelbeat.org/docs/openstack_libvirt_images/"
>The life of an OpenStack libvirt image from Pádraig
Brady</link>.</para>
@ -448,18 +465,29 @@ done</programlisting>
<tbody>
<tr>
<td>preallocate_images=none</td>
<td>(StrOpt) VM image preallocation mode: "none"
=&gt; no storage provisioning is done up
front, "space" =&gt; storage is fully
allocated at instance start. If this is set to
'space', the $instance_dir/ images will be 
<link
xlink:href="http://www.kernel.org/doc/man-pages/online/pages/man2/fallocate.2.html"
>fallocate</link>d to immediately
determine if enough space is available, and to
possibly improve VM I/O performance due to
ongoing allocation avoidance, and better
locality of block allocations.</td>
<td><para>(StrOpt) VM image preallocation
mode:</para><itemizedlist>
<listitem>
<para><literal>none</literal>. No
storage provisioning occurs up
front.</para>
</listitem>
<listitem>
<para><literal>space</literal>.
Storage is fully allocated at
instance start. The
<literal>$instance_dir/</literal>
images are <link
xlink:href="http://www.kernel.org/doc/man-pages/online/pages/man2/fallocate.2.html"
>fallocate</link>d to immediately
determine if enough space is
available, and to possibly improve
VM I/O performance due to ongoing
allocation avoidance, and better
locality of block
allocations.</para>
</listitem>
</itemizedlist></td>
</tr>
<tr>
<td>remove_unused_base_images=True</td>
@ -472,13 +500,13 @@ done</programlisting>
<tr>
<td>remove_unused_original_minimum_age_seconds=86400</td>
<td>(IntOpt) Unused unresized base images younger
than this will not be removed. Default is
86400 seconds, or 24 hours.</td>
than this are not removed. Default is 86400
seconds, or 24 hours.</td>
</tr>
<tr>
<td>remove_unused_resized_minimum_age_seconds=3600</td>
<td>(IntOpt) Unused resized base images younger
than this will not be removed. Default is 3600
than this are not removed. Default is 3600
seconds, or one hour.</td>
</tr>
</tbody>
@ -494,7 +522,7 @@ a0d1d5d3_20
2012-02-18 04:24:17 41389 INFO nova.virt.libvirt.imagecache [-] Removable base files: /var/lib/nova/instances/_base/06a057b9c7b0b27e3b496f53d1e88810
a0d1d5d3 /var/lib/nova/instances/_base/06a057b9c7b0b27e3b496f53d1e88810a0d1d5d3_20
2012-02-18 04:24:17 41389 INFO nova.virt.libvirt.imagecache [-] Removing base file: /var/lib/nova/instances/_base/06a057b9c7b0b27e3b496f53d1e88810a0d1d5d3</computeroutput></screen>
<para>Since 86400 seconds (24 hours) is the default time for
<para>Because 86400 seconds (24 hours) is the default time for
<literal>remove_unused_original_minimum_age_seconds</literal>,
you can either wait for that time interval to see the base
image removed, or set the value to a shorter time period