[node-devel] run ovirt-node in non-livecd mode

[Wenyi Gao]

On 2013-01-17 20:24, Mike Burns wrote:
> On Thu, 2013-01-17 at 09:43 +0800, Wenyi Gao wrote:
>> On 2013-01-16 19:47, Mike Burns wrote:
>>> On Wed, 2013-01-16 at 13:33 +0800, Wenyi Gao wrote:
>>>> Hey,
>>>>
>>>> Currently, the ovirt-node hypervisor runs in livecd mode, that is the
>>>> root filesystem is read-only.
>>>> We have to run "persist" command for persistent files, which is
>>>> inconvenient for some uses who
>>>> run ovirt-node only as hypervisor alone. So do we have plan to let
>>>> ovirt-node run non-livecd mode?
>>>> Thanks.
>>> Hi Wenyi,
>>>
>>> ovirt-node doesn't just run in livecd mode, it *is* a livecd.  If you're
>>> using ovirt-node with ovirt-engine (or derivative builds like RHEV-H
>>> with RHEV-M), then you shouldn't have any need to persist anything
>>> manually.  This is handled by the vdsm and ovirt-node packages
>>> automatically.
>>>
>>> There is no plan to let it run in any mode other than livecd.  There are
>>> other options in those cases, like running a full OS rather than an
>>> ovirt-node iso.
>>>
>>> Thanks
>>>
>>> Mike
>> Hi Mike,
>>
>> Thank you very much for answering the question. My case is we are using
>> ovirt-node
>> as hypervisor standalone without ovirt-engin or RHEV-M.
>>
>>
>> So could you have some ideas to keep the rootfs writeable into disks
>> persistently
>> not into  tmpfs? Like overlay file system?
> There isn't really a way unless you are building the image yourself from
> scratch, and even then, some things won't work as you would expect them
> to.
>
> One possibility:
>
>        * add / to the rwtab or an rwtab.d file -- this makes everything
>          writable, though not persistent.  It needs to be done at build
>          time, though.
>        * when installing, install with a very large Config partition.
>          It's 5MB by default, but you will need far more than that.
>        * persist the directories that you want persisted.  This will
>          automatically persist everything in those directories
>          to /config.  You probably don't want/need /var persisted since
>          that is generally runtime-only data.  /data /var/log and /config
>          are already backed by real storage, so no need to persist those
>          either.
>
> In general, I don't recommend this.  There may be things that just don't
> work the way you would expect.  The method for combining the 2
> filesystems is done through bind-mounts which happen during the boot
> process.  Therefore, some things that get persisted don't get
> bind-mounted early enough in the process to be used correctly.  These
> need special handling in the ovirt-early service.
>
> One other thing you could try is altering /etc/fstab in the base image
> to symbolically link some directory in /data.  /data is backed by real
> storage, so that would theoretically work as well and might be safer.
> The change needs to be done in the base image at build time or using
> something like a plugin to make this change.
>
> Hope this helps
>
> Mike
>

Your suggestions is very helpful, thank you very much.

Wenyi Gao
>>
>>>> Best regards
>>>> Wenyi Gao
>>>>
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>