[ubuntu-cloud] Cloud-config and mount points

[Bo Shi]

Thanks Scott, I'll give it a try.  As for ideas/code, I'm not
qualified to make any statement as I don't even know where the code
lives for the init code.  I'll try to report back when I get some time
to dive in.

On Wed, Jul 11, 2012 at 10:38 AM, Scott Moser <smoser at ubuntu.com> wrote:
> On Tue, 10 Jul 2012, Bo Shi wrote:
>
>> Hi,
>>
>> On an AWS EC2 instance, I'd like to switch /var/log from the root disk
>> to an ephemeral disk.  I can successfully change the mount point using
>> cloud-config:
>>
>>    mounts:
>>      - [ ephemeral0, /var/log, auto, "defaults,noexec" ]
>>
>>
>> One problem with this approach is that the actual mounts appear to be
>> occurring *after* rsyslog is started which blows away any existing
>> logs.  Does anyone know of a workaround?
>
>
> At times I've considered trying to make the mounts try to copy data
> across, but it seemed complex.  Ie, in the case given above, the code
> would have to know that rsyslog has to be restarted because it has handles
> to /var/log.
>
> That said, I think you might be able to accomplish what you want by
> running the 'mounts' cloud-config module as a 'cloud_init_modules' rather
> than 'cloud_config_modules'.
>
> basically, through user-data or image modification of
> /etc/cloud/cloud.cfg you should be able to do this:
>  | mounts:
>  |  - [ ephemeral0, /var/log, auto, "defaults,noexec" ]
>  | cloud_init_modules:
>  |  - bootcmd
>  |  - resizefs
>  |  - set_hostname
>  |  - update_hostname
>  |  - update_etc_hosts
>  |  - ca-certs
>  |  - rsyslog
>  |  - ssh
>  | cloud_config_modules:
>  |  - mounts
>  |  - ssh-import-id
>  |  - locale
>  |  - set-passwords
>  |  - grub-dpkg
>  |  - apt-pipelining
>  |  - apt-update-upgrade
>  |  - landscape
>  |  - timezone
>  |  - puppet
>  |  - chef
>  |  - salt-minion
>  |  - mcollective
>  |  - disable-ec2-metadata
>  |  - runcmd
>  |  - byobu
>
> Above, I basically copied content from /etc/cloud/cloud.cfg the data
> provided by user-data will override those stored in the image.
>
> I think that when run as a cloud-init module, cloud-init will actually
> block the running of rsyslog until it has finished.  So, at that point
> rsyslog should not have populated it.
>
> However, cloud-inti *will* have written some stuff to
> /var/log/cloud-init.log. so... thats one example of why this doesn't
> really work as well as you'd like.
>
> I'm open to ideas and code on how to make it magically work