Re: [Xen-devel] some thoughts on appstacks and app-tools

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Antti Kantee writes ("Re: some thoughts on appstacks and app-tools"):
> On 15/07/14 16:28, Ian Jackson wrote:
> > If that isn't happening already if you specify "ip=..." in the
> > appropriate place in the xl domain config file then there is a bug in
> > something, I think.
> 
> At least one bug is that I wasn't aware that it should happen ;)
> 
> Is the expected format documented somewhere?  E.g. ipv4 vs. ipv6, 
> default router, dhcp, etc?  xl-network-configuration is a little vague 
> about it.

No.  And as an OS author you are in theory looking at the wrong
document: that document is aimed at the host administrator.  In theory
you should be looking at the guest interface docs, of which the
relevant bit seems to be
  http://xenbits.xen.org/docs/unstable/misc/xenstore-paths.html
but sadly that doesn't mention the "ip" backend field.

> That said, ip= it might be good enough for a simple configuration, but 
> it will most likely fall short for e.g. a router/firewall.  I'm not sure 
> if an "rc script" should inline that type of configuration data, but if 
> that's literally all that the rc script doing, might be appropriate to 
> cut down the number of configuration files by allowing inlining.  <== 
> thinking out loud

Right.

> > I mean that the domain config file could say
> >    disk = [ "vdev=xvda, mountpoint=/etc, target=/path/to/blah.ffs" ]
> > and libxl would put the mountpoint info in xenstore so something
> > in the rump kernel Xen environment would pick it up.
> 
> Sounds good.  Can we pass arbitrary parameters a la fstab?

Not currently but perhaps we should be able to.

> > Busybox is a single application, not a build tool.  I wasn't aware of
> > crunchgen.  That does sound like it could do the job.
> 
> Ok.  They are usually mentioned together, so I thought busybox was the 
> Linux equivalent of crunchgen, kinda in the lsof(8) vs. fstat(1) sense. 

I don't know what crunchgen is other than what you have said here.
busybox is a reimplementation of a bunch of utilities written in such
a way that they can all be built into the same executable and dispatch
off argv[0].

So they don't sound very similar, although they solve some of the same
problem.

Notably, busybox's implementations are very minimal.  One of busybox's
aims is to be small (for installers, initramfs, etc.).  A traditional
GNU userland coreutils would be too big.  So no-one in the Linux world
would think of generating something to do busybox's job by smooshing
together coreutils ls and coreutils cat and so on.

ISTM that crunchgen might be useful, especially if there's a way to
specify whilch subsets of the BSD tools are included.  ls will be
quite fat compared to (say) mkdir and mknod.

> > I think it would be better to do this ad-hoc in the script language.
> 
> You're probably right ... at least until we run into the first 
> application that completely refuses to succumb to being backgrounded 
> like that.  But it sounds like a hurdle that can be crossed if it 
> appears at all.

Yes.

Ian.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
http://lists.xen.org/xen-devel