[Libguestfs] ZFS Support

[Miha Pleško]

Hi Richard, 

thanks for a quick reply. For now, I will not go into patching the libguestfs by myself 
since this is out of my scope. But I'm looking forward to see ZFS covered by this awesome 
library one day :D 

Regards, 
Miha 




----- Original Message -----

From: "Richard W.M. Jones" <rjones at redhat.com> 
To: "Miha Pleško" <miha.plesko at xlab.si> 
Cc: libguestfs at redhat.com 
Sent: Thursday, October 12, 2017 11:49:11 AM 
Subject: Re: [Libguestfs] ZFS Support 

On Thu, Oct 12, 2017 at 09:46:13AM +0200, Miha Pleško wrote: 
> 
> Dear libguestfs developers, 
> 
> as explained yesterday by Ubuntu guys on my bug report 
> https://bugs.launchpad.net/ubuntu/+source/libguestfs/+bug/1722800 
> 
> the libguestfs currently supports ZFS filesystem only partially 
> i.e. for virt-rescue. 
> 
> Q: Would it be possible to bring ZFS support also to other 
> libguestfs utils, like guestfish and virt-format? 
> 
> I would need to have two usecases supported: 

Thanks for posting here. As you say, ZFS support in libguestfs is 
currently very limited. Enabling it basically adds the userspace 
package so it's available in virt-rescue, if you manually use the 
‘zfs’/‘zpool’/etc commands. 

> a) create a new volume with ZFS filesystem / format existing volume 
> into ZFS filesystem 

We could fairly easily make simple things work like creating a 
filesystem. This is a good beginners patch as it just involves making 
simple adjustments to this function: 

https://github.com/libguestfs/libguestfs/blob/master/daemon/mkfs.c#L35 

> b) manage files from ZFS volume (read, write) 

I believe that mounting a ZFS volume should just work currently. If 
not, you might need to make only simple adjustments to the mount API: 

https://github.com/libguestfs/libguestfs/blob/master/daemon/mount.ml#L24 

This should allow you to read and write files. 

Providing full ZFS volume management is a quite a bit harder. It 
would involve pulling in some of the zfs APIs and turning them into 
libguestfs APIs. There is lots of documentation about how to add new 
APIs here: 

http://libguestfs.org/guestfs-hacking.1.html#extending-libguestfs 

I would start by looking at how other APIs have been implemented. 
Particularly relevant would be the LVM and btrfs APIs, eg: 

https://github.com/libguestfs/libguestfs/blob/master/daemon/btrfs.c 

Rich. 

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones 
Read my programming and virtualization blog: http://rwmj.wordpress.com 
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