Read-only view of a ZFS filesystem inside a bhyve guest?
Daniel Braniss
danny at cs.huji.ac.il
Sat Apr 28 11:28:24 UTC 2018
> On 28 Apr 2018, at 14:26, Daniel Braniss <danny at cs.huji.ac.il> wrote:
>
>
>
>> On 28 Apr 2018, at 13:37, Mark Raynsford <list+org.freebsd.virtualization at io7m.com> wrote:
>>
>> On 2018-04-28T09:08:42 +0300
>> Daniel Braniss <danny at cs.huji.ac.il> wrote:
>>
>>> since the clients and the server are sharing the zfs volume,
>>> I’m doing the following:
>>> on the server I did:
>>> zfs create -sV 4G h/root.ro <http://root.ro/>
>>> newfs /dev/zvol/h/root.ro <http://root.ro/>
>>> mount /dev/zol/h/root.ro <http://root.ro/> /mnt
>>> copy a working root image to it.
>>> umount /mnt
>>> the clients then mount it as ro,
>>> the vm conflg file has:
>>> disk0_type=virtio-blk”
>>> disk0_name=“/dev/zvol/h/root.ro <http://root.ro/>”
>>> disk0_dev=“custom”
>>>
>>> one solution to the fact that the root is read-only is to use unionfs (probably nullfs will do too)
>>>
>>> the only problem I have is updating the image.
>>
>> Wow, didn't know this was possible. Is this safe? Two essentially
>> independent operating system instances being able to write to the same
>> zvol?
>
> that’s why it’s mounted rear-only in the client!
grr, hate spell checkers, s/rear/read/ :-)
> each client can get another vol for writing, ie /var
> if you want to have ‘permanent’ changes that will survive reboots.
>
> updating on the server is possible, but
> 1- the changes might not be seen by the client
> 2- opened files will have issues
>
> btw, point 2 is also true for NFS.
>
> danny
>
>>
>> --
>> Mark Raynsford | http://www.io7m.com
>>
>
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