[lxc-users] [Help]LXD:point of differentiation. please answer my question

[John Siu]

> On Feb 20, 2016, at 02:39, 디케이 <zuntong at gmail.com> wrote:
> 
> Hi^^ 
> 
> Recently, I first know about LXD and I have searched information with great interest. 
> 
> (from articles, linuxcontainers.org <http://linuxcontainers.org/>, ubuntu product page)
> 
> But, until now, There are some parts that I can't yet understand.
> 
> That parts are very important for me. please anyswer my question below.
> 
> thanks in advance.
> 
>  
> 
> [Q1] I read that "LXD container provides a full OS environment within container." 
> 
>        So I think that is one of the Point of Differences beween LXD and other containers.
> 
>        Of course I know that app container like a docker does not support full OS envinronment.
> 
>        But before announcing LXD, already LXC technology has existed. well known technology. 
> 
>        Before LXD, Does LXC have already provided full OS environment??  
> 
>        I know other container like solaris zone also supports.
> 
> ( I know that LXD uses LXC, However I want to distinguish beween LXD new features and LXC origin feautre that have continued to support   before.)
> 
> 
>       Am I right? or wrong? 
> 
>       If I am wrong, 
> 
>      What is the main reason that LXD provides a full OS environment in comparison with lxc and zone??
> 
>       except for functions like a multiple hosts, snapshots.... just focus on full OS environment.
> 
> 

LXD is actually a management tool wrapper around LXC. LXC is the one that provide you the full OS container. LXD come with remote management capabilities, while LXC itself can only manage local containers.

So LXD is a LXC container manager. If you are familiar with VMware, you can think LXD as the VMSphere for LXC.

> [Q2] where can I get LXD manual? I have found a just few "get started webpage"
> 
>        I want to get "how to configure resource management", 
> 
>        how to assign block device and volume, how to connect container to outside and about configuraiotn files...
> 
> 

As far as I know, there are very limited documentation for LXD and LXC, not even ebook. Following blog series maybe helpful to you:

https://www.stgraber.org/2013/12/20/lxc-1-0-blog-post-series/
https://www.flockport.com/tag/lxc-3/

Both Flockport and Stéphane Graber's blog are very informative. Flockport is a bit more up to date, while Stéphane’s blog is more organized.
> [Q3] LXD container can not servcie itself by own funtion? 
> 
>        It means LXD container must use other tool like a SDN, openstack??
> 
>        (Docker can uses unixsocket, tcpsocket for service with other hosts, Docker does not need SDN)
> 
There is no LXD container. LXD manage LXC containers. LXD can be a standalone tools or work with Openstack, etc.

>  
> [Q4] All container technology use a host's kernel features (cgroup, namespace. etc...)
> 
>      I know LXD also use host's kernel features. 
> 
>      So VM like a virtubalbox, vmware can support better isolation and security than container.
> 
>      because VMs have own kernel and VMs does not share kernel resource.
> 
>      If so, How can LXD provide support better security and isolation than other container technology?? 
> 
Though cgroup have been in development for over 5yrs(or more?), IMHO it is still a new technology. The reason is it hasn’t been heavily tested and used till Docker, LXC and systemd ngspawn become available.

As with all technology, old or new, there will be bugs and security holes, and they will be fixed in time.
>     How can LXD be called linux hypervisor in comparison with other container(lxc, solaris zone)????.
> 
>  ( I know that LXD uses LXC, However I want to distinguish beween LXD new features and LXC origin feautre that have continued to support   before.)
> 
Again, as a simplified answer, LXC is comparable to Solaris Zone. They are both kernel level container, and the container use the host running kernel.

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