Diskless (Stateless) Installation¶

Note: The stateless Service Node is not supported in ubuntu hierarchy cluster. For ubuntu, skip this section.

If you want, your Service Nodes can be stateless (diskless). The Service Node must contain not only the OS, but also the xCAT software and its dependencies. In addition, a number of files are added to the Service Node to support the PostgreSQL, or MySQL database access from the Service Node to the Management node, and ssh access to the nodes that the Service Nodes services. The following sections explain how to accomplish this.

Build the Service Node Diskless Image¶

This section assumes you can build the stateless image on the management node because the Service Nodes are the same OS and architecture as the management node. If this is not the case, you need to build the image on a machine that matches the Service Node’s OS architecture.

Create an osimage definition. When you run copycds, xCAT will create a Service Node osimage definitions for that distribution. For a stateless Service Node, use the *-netboot-service definition.

# lsdef -t osimage | grep -i service
rhels6.4-ppc64-install-service  (osimage)
rhels6.4-ppc64-netboot-service  (osimage)  <================
rhels6.4-ppc64-statelite-service  (osimage)

# lsdef -t osimage -l rhels6.3-ppc64-netboot-service
Object name: rhels6.3-ppc64-netboot-service
    exlist=/opt/xcat/share/xcat/netboot/rh/service.exlist
    imagetype=linux
    osarch=ppc64
    osdistroname=rhels6.3-ppc64
    osname=Linux
    osvers=rhels6.3
    otherpkgdir=/install/post/otherpkgs/rhels6.3/ppc64
    otherpkglist=/opt/xcat/share/xcat/netboot/rh/service.rhels6.ppc64.otherpkgs.pkglist
    pkgdir=/install/rhels6.3/ppc64
    pkglist=/opt/xcat/share/xcat/netboot/rh/service.rhels6.ppc64.pkglist
    postinstall=/opt/xcat/share/xcat/netboot/rh/service.rhels6.ppc64.postinstall
    profile=service
    provmethod=netboot
    rootimgdir=/install/netboot/rhels6.3/ppc64/service

You can check the Service Node packaging to see if it has all the rpms you require. We ship a basic requirements lists that will create a fully functional Service Node. However, you may want to customize your service node by adding additional operating system packages or modifying the files excluded by the exclude list. View the files referenced by the osimage pkglist, otherpkglist and exlist attributes:
```
cd /opt/xcat/share/xcat/netboot/rh/
view service.rhels6.ppc64.pkglist
view service.rhels6.ppc64.otherpkgs.pkglist
view service.exlist
```
If you would like to change any of these files, copy them to a custom directory. This can be any directory you choose, but we recommend that you keep it /install somewhere. A good location is something like /install/custom/netboot/<os>/service. Make sure that your otherpkgs.pkglist file as an entry for
```
xcat/xcat-core/xCATsn
```
This is required to install the xCAT Service Node function into your image.

You may also choose to create an appropriate /etc/fstab file in your Service Node image. Copy the script referenced by the postinstall attribute to your directory and modify it as you would like:
```
cp /opt/xcat/share/xcat/netboot/rh/service.rhels6.ppc64.postinstall
/install/custom/netboot/rh
vi /install/custom/netboot/rh
# uncomment the sample fstab lines and change as needed:
proc /proc proc rw 0 0
sysfs /sys sysfs rw 0 0
devpts /dev/pts devpts rw,gid=5,mode=620 0 0
service_x86_64 / tmpfs rw 0 1
none /tmp tmpfs defaults,size=10m 0 2
none /var/tmp tmpfs defaults,size=10m 0 2
```
After modifying the files, you will need to update the osimage definition to reference these files. We recommend creating a new osimage definition for your custom image:
```
lsdef -t osimage -l rhels6.3-ppc64-netboot-service -z > /tmp/myservice.def
vi /tmp/myservice.def
# change the name of the osimage definition
# change any attributes that now need to reference your custom files
# change the rootimgdir attribute replacing 'service'
with a name to match your new osimage definition
cat /tmp/msyservice.def | mkdef -z
```
While you are here, if you’d like, you can do the same for your compute node images, creating custom files and new custom osimage definitions as you need to.
Make your xCAT software available for otherpkgs processing

If you downloaded xCAT to your management node for installation, place a copy of your xcat-core and xcat-dep in your otherpkgdir directory

lsdef -t osimage -o rhels6.3-ppc64-netboot-service -i otherpkgdir
Object name: rhels6.3-ppc64-netboot-service
otherpkgdir=/install/post/otherpkgs/rhels6.3/ppc64
cd /install/post/otherpkgs/rhels6.3/ppc64
mkdir xcat
cd xcat
cp -Rp <current location of xcat-core>/xcat-core
cp -Rp <current location of xcat-dep>/xcat-dep

If you installed your management node directly from the online repository, you will need to download the xcat-core and xcat-dep tarballs

From http://xcat.org/download.html, download the xcat-core and xcat-dep tarball files. Copy these into a subdirectory in the otherpkgdir directory.

lsdef -t osimage -o rhels6.3-ppc64-netboot-service -i otherpkgdir
Object name: rhels6.3-ppc64-netboot-service
    otherpkgdir=/install/post/otherpkgs/rhels6.3/ppc64

cd /install/post/otherpkgs/rhels6.3/ppc64
mkdir xcat
cd xcat

# copy the <xcat-core> and <xcat-deb> tarballs here

# extract the tarballs
tar -jxvf <xcat-core>.tar.bz2
tar -jxvf <xcat-dep>.tar.bz2

Run image generation for your osimage definition:
```
genimage rhels6.3-ppc64-netboot-service
```

Prevent DHCP from starting up until xcatd has had a chance to configure it:

chroot /install/netboot/rhels6.3/ppc64/service/rootimg chkconfig dhcpd off
chroot /install/netboot/rhels6.3/ppc64/service/rootimg chkconfig dhcrelay off

IF using NFS hybrid mode, export /install read-only in Service Node image:

cd /install/netboot/rhels6.3/ppc64/service/rootimg/etc
echo '/install *(ro,no_root_squash,sync,fsid=13)' >exports

Pack the image for your osimage definition:

packimage rhels6.3-ppc64-netboot-service

Set the node status to ready for netboot using your osimage definition and your ‘service’ nodegroup:
```
nodeset service osimage=rhels6.3-ppc64-netboot-service
```
To diskless boot the Service Nodes

rnetboot service

Update Service Node Stateless Image¶

To update the xCAT software in the image at a later time:

Download the updated xcat-core and xcat-dep tarballs and place them in your osimage’s otherpkgdir xcat directory as you did above.

Generate and repack the image and reboot your Service Node.

Run image generation for your osimage definition.
genimage rhels6.3-ppc64-netboot-service
packimage rhels6.3-ppc64-netboot-service
nodeset service osimage=rhels6.3-ppc64-netboot-service
rnetboot service

Note: The Service Nodes are set up as NFS-root servers for the compute nodes. Any time changes are made to any compute image on the mgmt node it will be necessary to sync all changes to all Service Nodes. In our case the /install directory is mounted on the servicenodes, so the update to the compute node image is automatically available.

Monitor install and boot¶

wcons service # make sure DISPLAY is set to your X server/VNC or
rcons <one-node-at-a-time> # or do rcons for each node
tail -f /var/log/messages