[one-users] Reference CONTEXT variables within CONTEXT

[Valentin Bud]

Hello Community,

First of all, I apologise I forgot to say hi in my previous E-Mail :|.

On Thu, May 16, 2013 at 10:28:14AM +0300, Valentin Bud wrote:
> I am trying to reference the CONTEXT variables from within CONTEXT.
> 
> For example, I define the DOMAIN="domain.tld" and the HOSTNAME="host".
> I would like to have a variable FQDN="$HOST.$DOMAIN.".
> 
> I have tried to achieve the above using the following in CONTEXT section
> of the template.
> 
> Case I
> --
> 
> $ onetemplate show vars
> 
> TEMPLATE CONTENTS
> CONTEXT=[
>   DOMAIN="domain.tld",
>   FQDN="$DOMAIN.$HOSTNAME.",
>   HOSTNAME="host" ]
> 
> [... output omitted for brevity ...]
> 
> Instantiating the template results in the following variables added to
> the VM.
> 
> $ onevm show vars
> 
> VIRTUAL MACHINE TEMPLATE
> CONTEXT=[
>   DISK_ID="1",
>   DOMAIN="domain.tld",
>   *FQDN="..",*
>   HOSTNAME="host",
>   TARGET="hda" ]
> 
> Case II
> --
> 
> $ onetemplate show vars
> 
> CONTEXT=[
>   DOMAIN="domain.tld",
>   FQDN="$CONTEXT[$DOMAIN].$CONTEXT[$HOSTNAME].",
>   HOSTNAME="host" ]
> [... output omitted for brevity ...]
> 
> Same result in the VM.
> 
> $ onevm show vars
> 
> VIRTUAL MACHINE TEMPLATE
> CONTEXT=[
>   DISK_ID="1",
>   DOMAIN="domain.tld",
>   *FQDN=".."*,
>   HOSTNAME="host",
>   TARGET="hda" ]
> [... output omitted for brevity ...]
> 
> Is it possible to achieve what am I trying or should I search for a new
> solution?
> 
> I have a simple use case. I am generating, via a hook, the ssh keys for
> the VM in question. At boot I copy the keys from /mnt to /etc/ssh via 
> a crafted one-context script. Awesome mechanism by the way :-).
> 
> I am generating the keys in
> CONTEXT_FILES_LOCATION=/var/lib/cloud/context/host.domain.tld.
> 
> I would like to use the following in the CONTEXT section:
> 
> CONTEXT=[
> CONTEXT_FILES_LOCATION=/var/lib/cloud/context/host.domain.tld./,
> DOMAIN="domain.tld",
> FILES="$CONTEXT_FILES_LOCATION/$FQDN/ssh_host_rsa_key ...",
> HOSTNAME="host",
> FQDN="$HOSTNAME.$DOMAIN." ]
> 
> This makes the template much more dynamic. I would just change the HOSTNAME
> and the paths would get generated dynamically.
> 

Writing the HOSTNAME, DOMAIN, CONTEXT_FILES_LOCATION outside the CONTEXT
section and referencing them from within CONTEXT works :-).

Example
--

$ onetemplate show vars

TEMPLATE CONTENTS
CONTEXT=[
  CONTEXT_FILES_LOCATION="$CONTEXT_FILES_LOCATION",
  DOMAIN="$DOMAIN",
  FILES="$CONTEXT_FILES_LOCATION/$FQDN/ssh_host_rsa_key
  $CONTEXT_FILES_LOCATION/$FQDN/ssh_host_rsa_key.pub",
  FQDN="$HOSTNAME.$DOMAIN.",
  HOSTNAME="$HOSTNAME" ]
CONTEXT_FILES_LOCATION="/var/lib/cloud/context"
CPU="1"
DISK=[
  IMAGE="vars" ]
DOMAIN="domain.tld"
GRAPHICS=[
  LISTEN="0.0.0.0",
  TYPE="vnc" ]
HOSTNAME="host"
MEMORY="2048"
NIC=[
  NETWORK="host.domain.tld" ]
OS=[
  ARCH="x86_64" ]
VCPU="4"

After instantiating the machine I have the desired results.

$ onevm show vars

VIRTUAL MACHINE TEMPLATE
CONTEXT=[
  CONTEXT_FILES_LOCATION="/var/lib/cloud/context",
  DISK_ID="1",
  DOMAIN="dev.corview.de",
  FILES="/var/lib/cloud/context//ssh_host_rsa_key
  /var/lib/cloud/context//ssh_host_rsa_key.pub",
  FQDN="vars.domain.tld.",
  HOSTNAME="vars",
  TARGET="hda" ]

Now I can easily generate SSH host keys for each machine if this wasn't
done already in a previous VM instantation.

Thanks and sorry for the noise. If this is mentioned somewhere in the
docs, my bad.

Cheers and Goodwill,

--
Valentin Bud
http://databus.pro/ | valentin at databus.pro