bcec02416e
Another round of typos/spelling errors fixing, in particular for config-reference, HA guide and image guide. Change-Id: Ibc3661e132a0ea4010a5a61f71ef5209ae6655b6 Closes-Bug: #1356970
535 lines
27 KiB
XML
535 lines
27 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
|
|
<!DOCTYPE chapter [
|
|
<!ENTITY % openstack SYSTEM "../common/entities/openstack.ent">
|
|
%openstack;
|
|
]>
|
|
<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"
|
|
xml:id="ch_openstack_images">
|
|
<title>OpenStack Linux image requirements</title>
|
|
<?dbhtml stop-chunking?>
|
|
<para>For a Linux-based image to have full functionality in an
|
|
OpenStack Compute cloud, there are a few requirements. For
|
|
some of these, you can fulfill the requirement by installing
|
|
the <link
|
|
xlink:href="https://cloudinit.readthedocs.org/en/latest/"
|
|
><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 to use.</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 <
|
|
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 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 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 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: One ext3/ext4
|
|
partition (no LVM, no /boot, no swap)</title>
|
|
<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"
|
|
>cloud-utils</link> package (contains the
|
|
<command>growpart</command> tool for extending
|
|
partitions), the <link
|
|
xlink:href="https://launchpad.net/cloud-initramfs-tools"
|
|
>cloud-initramfs-growroot</link> package (which
|
|
supports resizing root partition on the first boot),
|
|
and the <link
|
|
xlink:href="https://launchpad.net/cloud-init"
|
|
><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 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
|
|
<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
|
|
the output of <command>parted /dev/sda
|
|
--script "print
|
|
free"</command>.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Create a new LVM partition with the
|
|
additional space. For example,
|
|
<command>parted /dev/sda --script
|
|
"mkpart lvm ..."</command>.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Create a new physical volume. For
|
|
example, <command>pvcreate
|
|
/dev/<replaceable>sda6</replaceable></command>.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Extend the volume group with this
|
|
physical partition. For example,
|
|
<command>vgextend
|
|
<replaceable>vg00</replaceable>
|
|
/dev/<replaceable>sda6</replaceable></command>.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Extend the logical volume contained the
|
|
root partition by the amount of space. For
|
|
example, <command>lvextend
|
|
/dev/mapper/<replaceable>node-root</replaceable>
|
|
/dev/<replaceable>sda6</replaceable></command>.</para>
|
|
</listitem>
|
|
<listitem>
|
|
<para>Resize the root file system. For
|
|
example, <command>resize2fs
|
|
/dev/mapper/<replaceable>node-root</replaceable></command>.</para>
|
|
</listitem>
|
|
</orderedlist></para>
|
|
<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.</para>
|
|
</simplesect>
|
|
</section>
|
|
<section xml:id="mac-address">
|
|
<title>No hard-coded MAC address information</title>
|
|
<para>You must remove the network persistence rules in the
|
|
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 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
|
|
inside of your image and use OpenStack security groups to
|
|
restrict access to instances. The reason is that having a
|
|
firewall installed on your instance can make it more
|
|
difficult to troubleshoot networking issues if you cannot
|
|
connect to your instance.</para>
|
|
</section>
|
|
<section xml:id="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
|
|
authentication. For this to work, your virtual machine
|
|
image must be configured to download the ssh public key
|
|
from the OpenStack metadata service or config drive, at
|
|
boot time.</para>
|
|
<simplesect>
|
|
<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
|
|
<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 <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
|
|
<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
|
|
“touch /var/lock/subsys/local”. This code fragment is
|
|
taken from the <link
|
|
xlink:href="https://github.com/rackerjoe/oz-image-build/blob/master/templates/centos60_x86_64.tdl"
|
|
>rackerjoe oz-image-build CentOS 6
|
|
template</link>.</para>
|
|
<programlisting language="bash">if [ ! -d /root/.ssh ]; then
|
|
mkdir -p /root/.ssh
|
|
chmod 700 /root/.ssh
|
|
fi
|
|
|
|
# Fetch public key using HTTP
|
|
ATTEMPTS=30
|
|
FAILED=0
|
|
while [ ! -f /root/.ssh/authorized_keys ]; do
|
|
curl -f http://169.254.169.254/latest/meta-data/public-keys/0/openssh-key > /tmp/metadata-key 2>/dev/null
|
|
if [ $? -eq 0 ]; then
|
|
cat /tmp/metadata-key >> /root/.ssh/authorized_keys
|
|
chmod 0600 /root/.ssh/authorized_keys
|
|
restorecon /root/.ssh/authorized_keys
|
|
rm -f /tmp/metadata-key
|
|
echo "Successfully retrieved public key from instance metadata"
|
|
echo "*****************"
|
|
echo "AUTHORIZED KEYS"
|
|
echo "*****************"
|
|
cat /root/.ssh/authorized_keys
|
|
echo "*****************"
|
|
else
|
|
FAILED=`expr $FAILED + 1`
|
|
if [ $FAILED -ge $ATTEMPTS ]; then
|
|
echo "Failed to retrieve public key from instance metadata after $FAILED attempts, quitting"
|
|
break
|
|
fi
|
|
echo "Could not retrieve public key from instance metadata (attempt #$FAILED/$ATTEMPTS), retrying in 5 seconds..."
|
|
sleep 5
|
|
fi
|
|
done</programlisting>
|
|
<note>
|
|
<para>Some VNC clients replace : (colon) with ;
|
|
(semicolon) and _ (underscore) with - (hyphen). If
|
|
editing a file over a VNC session, make sure it's
|
|
http: not http; and authorized_keys not
|
|
authorized-keys.</para>
|
|
</note>
|
|
|
|
|
|
</simplesect>
|
|
|
|
</section>
|
|
<section xml:id="metadata">
|
|
<title>Process user data and other metadata
|
|
(cloud-init)</title>
|
|
<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
|
|
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
|
|
Amazon EC2 metadata service, consult the Amazon EC2
|
|
documentation on <link
|
|
xlink:href="http://docs.amazonwebservices.com/AWSEC2/2009-04-04/UserGuide/AESDG-chapter-instancedata.html"
|
|
>Using Instance Metadata</link> for details on how to
|
|
retrieve user data.</para>
|
|
|
|
<para>The easiest way to support this type of functionality is
|
|
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>
|
|
<para>You must configure the image so that the kernel writes
|
|
the boot log to the <literal>ttyS0</literal> device. In
|
|
particular, the <literal>console=ttyS0</literal> argument
|
|
must be passed to the kernel on boot.</para>
|
|
<para>If your image uses grub2 as the boot loader, there
|
|
should be a line in the grub configuration file. For
|
|
example, <filename>/boot/grub/grub.cfg</filename>, which
|
|
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
|
|
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
|
|
operating-systems such as Ubuntu, run this command:</para>
|
|
<screen><prompt>#</prompt> <userinput>update-grub</userinput></screen>
|
|
<para>On Fedora-based systems, such as RHEL and CentOS, and on
|
|
openSUSE, run this command:</para>
|
|
<screen><prompt>#</prompt> <userinput>grub2-mkconfig -o /boot/grub2/grub.cfg</userinput></screen>
|
|
</section>
|
|
<section xml:id="image-xen-pv">
|
|
<title>Paravirtualized Xen support in the kernel (Xen
|
|
hypervisor only)</title>
|
|
<para>Prior to Linux kernel version 3.0, the mainline branch
|
|
of the Linux kernel did not have support paravirtualized
|
|
Xen virtual machine instances (what Xen calls DomU
|
|
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
|
|
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>
|
|
<para>Use options in <filename>nova.conf</filename> to control
|
|
whether, and for how long, unused base images are stored
|
|
in <filename>/var/lib/nova/instances/_base/</filename>. If
|
|
you have configured live migration of instances, all your
|
|
compute nodes share one common
|
|
<filename>/var/lib/nova/instances/</filename>
|
|
directory.</para>
|
|
<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>
|
|
<table rules="all">
|
|
<caption>Image cache management configuration
|
|
options</caption>
|
|
<col width="50%"/>
|
|
<col width="50%"/>
|
|
<thead>
|
|
<tr>
|
|
<td>Configuration option=Default value</td>
|
|
<td>(Type) Description</td>
|
|
</tr>
|
|
</thead>
|
|
<tbody>
|
|
<tr>
|
|
<td>preallocate_images=none</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>
|
|
<td>(BoolOpt) Should unused base images be
|
|
removed? When set to True, the interval at
|
|
which base images are removed are set with the
|
|
following two settings. If set to False base
|
|
images are never removed by Compute.</td>
|
|
</tr>
|
|
<tr>
|
|
<td>remove_unused_original_minimum_age_seconds=86400</td>
|
|
<td>(IntOpt) Unused unresized base images younger
|
|
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 are not removed. Default is 3600
|
|
seconds, or one hour.</td>
|
|
</tr>
|
|
</tbody>
|
|
</table>
|
|
<para>To see how the settings affect the deletion of a running
|
|
instance, check the directory where the images are
|
|
stored:</para>
|
|
<screen><prompt>#</prompt> <userinput>ls -lash /var/lib/nova/instances/_base/</userinput></screen>
|
|
<para>In the <filename>/var/log/compute/compute.log</filename>
|
|
file, look for the identifier:</para>
|
|
<screen><computeroutput>2012-02-18 04:24:17 41389 WARNING nova.virt.libvirt.imagecache [-] Unknown base file: /var/lib/nova/instances/_base/06a057b9c7b0b27e3b496f53d1e88810
|
|
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>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
|
|
in <filename>nova.conf</filename>. Restart all nova
|
|
services after changing a setting in
|
|
<filename>nova.conf</filename>.</para>
|
|
</section>
|
|
</chapter>
|